Skip to main content

Home/ Larvata/ Group items tagged code

Rss Feed Group items tagged

Filter: All | Bookmarks | Topics Simple Middle
張 旭

Active Record Associations - Ruby on Rails Guides - 0 views

guides.rubyonrails.org/association_basics.html

rails database ruby relation

shared by 張 旭 on 12 Apr 16 - Cached
  • With Active Record associations, we can streamline these - and other - operations by declaratively telling Rails that there is a connection between the two models.
  • belongs_to has_one has_many has_many :through has_one :through has_and_belongs_to_many
  • an association is a connection between two Active Record models
  • ...195 more annotations...
  • Associations are implemented using macro-style calls, so that you can declaratively add features to your models
  • A belongs_to association sets up a one-to-one connection with another model, such that each instance of the declaring model "belongs to" one instance of the other model.
  • belongs_to associations must use the singular term.
  • belongs_to
  • A has_one association also sets up a one-to-one connection with another model, but with somewhat different semantics (and consequences).
  • This association indicates that each instance of a model contains or possesses one instance of another model
  • belongs_to
  • A has_many association indicates a one-to-many connection with another model.
  • This association indicates that each instance of the model has zero or more instances of another model.
  • belongs_to
  • A has_many :through association is often used to set up a many-to-many connection with another model
  • This association indicates that the declaring model can be matched with zero or more instances of another model by proceeding through a third model.
  • through:
  • through:
  • The collection of join models can be managed via the API
  • new join models are created for newly associated objects, and if some are gone their rows are deleted.
  • The has_many :through association is also useful for setting up "shortcuts" through nested has_many associations
  • A has_one :through association sets up a one-to-one connection with another model. This association indicates that the declaring model can be matched with one instance of another model by proceeding through a third model.
  • A has_and_belongs_to_many association creates a direct many-to-many connection with another model, with no intervening model.
  • id: false
  • The has_one relationship says that one of something is yours
  • using t.references :supplier instead.
  • declare a many-to-many relationship is to use has_many :through. This makes the association indirectly, through a join model
  • set up a has_many :through relationship if you need to work with the relationship model as an independent entity
  • set up a has_and_belongs_to_many relationship (though you'll need to remember to create the joining table in the database).
  • use has_many :through if you need validations, callbacks, or extra attributes on the join model
  • With polymorphic associations, a model can belong to more than one other model, on a single association.
  • belongs_to :imageable, polymorphic: true
  • a polymorphic belongs_to declaration as setting up an interface that any other model can use.
    • 張 旭
      張 旭 on 13 Apr 16
       
      _id 記錄的是不同類型的外連鍵 id；_type 記錄的是不同類型的表格名稱。
  • In designing a data model, you will sometimes find a model that should have a relation to itself
  • add a references column to the model itself
  • Controlling caching Avoiding name collisions Updating the schema Controlling association scope Bi-directional associations
  • All of the association methods are built around caching, which keeps the result of the most recent query available for further operations.
  • it is a bad idea to give an association a name that is already used for an instance method of ActiveRecord::Base. The association method would override the base method and break things.
  • You are responsible for maintaining your database schema to match your associations.
  • belongs_to associations you need to create foreign keys
  • has_and_belongs_to_many associations you need to create the appropriate join table
  • If you create an association some time after you build the underlying model, you need to remember to create an add_column migration to provide the necessary foreign key.
  • Active Record creates the name by using the lexical order of the class names
  • So a join between customer and order models will give the default join table name of "customers_orders" because "c" outranks "o" in lexical ordering.
  • For example, one would expect the tables "paper_boxes" and "papers" to generate a join table name of "papers_paper_boxes" because of the length of the name "paper_boxes", but it in fact generates a join table name of "paper_boxes_papers" (because the underscore '' is lexicographically _less than 's' in common encodings).
  • id: false
  • pass id: false to create_table because that table does not represent a model
  • By default, associations look for objects only within the current module's scope.
  • will work fine, because both the Supplier and the Account class are defined within the same scope.
  • To associate a model with a model in a different namespace, you must specify the complete class name in your association declaration:
  • class_name
  • class_name
  • Active Record provides the :inverse_of option
    • 張 旭
      張 旭 on 13 Apr 16
       
      意思是說第一次比較兩者的 first_name 是相同的；但透過 c 實體修改 first_name 之後，再次比較就不相同了，因為兩個是記憶體裡面兩個不同的物件。
  • preventing inconsistencies and making your application more efficient
  • Every association will attempt to automatically find the inverse association and set the :inverse_of option heuristically (based on the association name)
  • In database terms, this association says that this class contains the foreign key.
  • In all of these methods, association is replaced with the symbol passed as the first argument to belongs_to.
  • (force_reload = false)
  • The association method returns the associated object, if any. If no associated object is found, it returns nil.
  • the cached version will be returned.
  • The association= method assigns an associated object to this object.
  • Behind the scenes, this means extracting the primary key from the associate object and setting this object's foreign key to the same value.
  • The build_association method returns a new object of the associated type
  • but the associated object will not yet be saved.
  • The create_association method returns a new object of the associated type
  • once it passes all of the validations specified on the associated model, the associated object will be saved
  • raises ActiveRecord::RecordInvalid if the record is invalid.
  • dependent
  • counter_cache
  • :autosave :class_name :counter_cache :dependent :foreign_key :inverse_of :polymorphic :touch :validate
  • finding the number of belonging objects more efficient.
  • Although the :counter_cache option is specified on the model that includes the belongs_to declaration, the actual column must be added to the associated model.
  • add a column named orders_count to the Customer model.
  • :destroy, when the object is destroyed, destroy will be called on its associated objects.
  • deleted directly from the database without calling their destroy method.
  • Rails will not create foreign key columns for you
  • The :inverse_of option specifies the name of the has_many or has_one association that is the inverse of this association
  • set the :touch option to :true, then the updated_at or updated_on timestamp on the associated object will be set to the current time whenever this object is saved or destroyed
  • specify a particular timestamp attribute to update
  • If you set the :validate option to true, then associated objects will be validated whenever you save this object
  • By default, this is false: associated objects will not be validated when this object is saved.
  • where includes readonly select
  • make your code somewhat more efficient
  • no need to use includes for immediate associations
  • will be read-only when retrieved via the association
  • The select method lets you override the SQL SELECT clause that is used to retrieve data about the associated object
  • using the association.nil?
  • Assigning an object to a belongs_to association does not automatically save the object. It does not save the associated object either.
  • In database terms, this association says that the other class contains the foreign key.
  • the cached version will be returned.
  • :as :autosave :class_name :dependent :foreign_key :inverse_of :primary_key :source :source_type :through :validate
  • Setting the :as option indicates that this is a polymorphic association
  • :nullify causes the foreign key to be set to NULL. Callbacks are not executed.
  • It's necessary not to set or leave :nullify option for those associations that have NOT NULL database constraints.
  • The :source_type option specifies the source association type for a has_one :through association that proceeds through a polymorphic association.
  • The :source option specifies the source association name for a has_one :through association.
  • The :through option specifies a join model through which to perform the query
  • more efficient by including representatives in the association from suppliers to accounts
  • When you assign an object to a has_one association, that object is automatically saved (in order to update its foreign key).
  • If either of these saves fails due to validation errors, then the assignment statement returns false and the assignment itself is cancelled.
  • If the parent object (the one declaring the has_one association) is unsaved (that is, new_record? returns true) then the child objects are not saved.
  • If you want to assign an object to a has_one association without saving the object, use the association.build method
  • collection(force_reload = false) collection<<(object, ...) collection.delete(object, ...) collection.destroy(object, ...) collection=(objects) collection_singular_ids collection_singular_ids=(ids) collection.clear collection.empty? collection.size collection.find(...) collection.where(...) collection.exists?(...) collection.build(attributes = {}, ...) collection.create(attributes = {}) collection.create!(attributes = {})
  • In all of these methods, collection is replaced with the symbol passed as the first argument to has_many, and collection_singular is replaced with the singularized version of that symbol.
  • The collection<< method adds one or more objects to the collection by setting their foreign keys to the primary key of the calling model
  • The collection.delete method removes one or more objects from the collection by setting their foreign keys to NULL.
  • objects will be destroyed if they're associated with dependent: :destroy, and deleted if they're associated with dependent: :delete_all
  • The collection.destroy method removes one or more objects from the collection by running destroy on each object.
  • The collection_singular_ids method returns an array of the ids of the objects in the collection.
  • The collection_singular_ids= method makes the collection contain only the objects identified by the supplied primary key values, by adding and deleting as appropriate
  • The default strategy for has_many :through associations is delete_all, and for has_many associations is to set the foreign keys to NULL.
  • The collection.clear method removes all objects from the collection according to the strategy specified by the dependent option
  • uses the same syntax and options as ActiveRecord::Base.find
  • The collection.where method finds objects within the collection based on the conditions supplied but the objects are loaded lazily meaning that the database is queried only when the object(s) are accessed.
  • The collection.build method returns one or more new objects of the associated type. These objects will be instantiated from the passed attributes, and the link through their foreign key will be created, but the associated objects will not yet be saved.
  • The collection.create method returns a new object of the associated type. This object will be instantiated from the passed attributes, the link through its foreign key will be created, and, once it passes all of the validations specified on the associated model, the associated object will be saved.
  • :as :autosave :class_name :dependent :foreign_key :inverse_of :primary_key :source :source_type :through :validate
  • :delete_all causes all the associated objects to be deleted directly from the database (so callbacks will not execute)
  • :nullify causes the foreign keys to be set to NULL. Callbacks are not executed.
  • where includes readonly select
  • :conditions :through :polymorphic :foreign_key
  • By convention, Rails assumes that the column used to hold the primary key of the association is id. You can override this and explicitly specify the primary key with the :primary_key option.
  • The :source option specifies the source association name for a has_many :through association.
  • You only need to use this option if the name of the source association cannot be automatically inferred from the association name.
  • The :source_type option specifies the source association type for a has_many :through association that proceeds through a polymorphic association.
  • The :through option specifies a join model through which to perform the query.
  • has_many :through associations provide a way to implement many-to-many relationships,
  • By default, this is true: associated objects will be validated when this object is saved.
  • where extending group includes limit offset order readonly select uniq
  • If you use a hash-style where option, then record creation via this association will be automatically scoped using the hash
  • The extending method specifies a named module to extend the association proxy.
  • Association extensions
  • The group method supplies an attribute name to group the result set by, using a GROUP BY clause in the finder SQL.
  • has_many :line_items, -> { group 'orders.id' },                        through: :orders
  • more efficient by including line items in the association from customers to orders
  • The limit method lets you restrict the total number of objects that will be fetched through an association.
  • The offset method lets you specify the starting offset for fetching objects via an association
  • The order method dictates the order in which associated objects will be received (in the syntax used by an SQL ORDER BY clause).
  • Use the distinct method to keep the collection free of duplicates.
  • mostly useful together with the :through option
  • -> { distinct }
  • .all.inspect
  • If you want to make sure that, upon insertion, all of the records in the persisted association are distinct (so that you can be sure that when you inspect the association that you will never find duplicate records), you should add a unique index on the table itself
  • unique: true
  • Do not attempt to use include? to enforce distinctness in an association.
  • multiple users could be attempting this at the same time
  • checking for uniqueness using something like include? is subject to race conditions
  • When you assign an object to a has_many association, that object is automatically saved (in order to update its foreign key).
  • If any of these saves fails due to validation errors, then the assignment statement returns false and the assignment itself is cancelled.
  • If the parent object (the one declaring the has_many association) is unsaved (that is, new_record? returns true) then the child objects are not saved when they are added
  • All unsaved members of the association will automatically be saved when the parent is saved.
  • assign an object to a has_many association without saving the object, use the collection.build method
  • collection(force_reload = false) collection<<(object, ...) collection.delete(object, ...) collection.destroy(object, ...) collection=(objects) collection_singular_ids collection_singular_ids=(ids) collection.clear collection.empty? collection.size collection.find(...) collection.where(...) collection.exists?(...) collection.build(attributes = {}) collection.create(attributes = {}) collection.create!(attributes = {})
  • If the join table for a has_and_belongs_to_many association has additional columns beyond the two foreign keys, these columns will be added as attributes to records retrieved via that association.
  • Records returned with additional attributes will always be read-only
  • If you require this sort of complex behavior on the table that joins two models in a many-to-many relationship, you should use a has_many :through association instead of has_and_belongs_to_many.
  • aliased as collection.concat and collection.push.
  • The collection.delete method removes one or more objects from the collection by deleting records in the join table
  • not destroy the objects
  • The collection.destroy method removes one or more objects from the collection by running destroy on each record in the join table, including running callbacks.
  • not destroy the objects.
  • The collection.clear method removes every object from the collection by deleting the rows from the joining table.
  • not destroy the associated objects.
  • The collection.find method finds objects within the collection. It uses the same syntax and options as ActiveRecord::Base.find.
  • The collection.where method finds objects within the collection based on the conditions supplied but the objects are loaded lazily meaning that the database is queried only when the object(s) are accessed.
  • The collection.exists? method checks whether an object meeting the supplied conditions exists in the collection.
  • The collection.build method returns a new object of the associated type.
  • the associated object will not yet be saved.
  • the associated object will be saved.
  • The collection.create method returns a new object of the associated type.
  • it passes all of the validations specified on the associated model
  • :association_foreign_key :autosave :class_name :foreign_key :join_table :validate
  • The :foreign_key and :association_foreign_key options are useful when setting up a many-to-many self-join.
  • Rails assumes that the column in the join table used to hold the foreign key pointing to the other model is the name of that model with the suffix _id added.
  • If you set the :autosave option to true, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
  • By convention, Rails assumes that the column in the join table used to hold the foreign key pointing to this model is the name of this model with the suffix _id added.
  • By default, this is true: associated objects will be validated when this object is saved.
  • where extending group includes limit offset order readonly select uniq
  • set conditions via a hash
  • In this case, using @parts.assemblies.create or @parts.assemblies.build will create orders where the factory column has the value "Seattle"
  • If you use a hash-style where, then record creation via this association will be automatically scoped using the hash
  • using a GROUP BY clause in the finder SQL.
  • Use the uniq method to remove duplicates from the collection.
  • assign an object to a has_and_belongs_to_many association, that object is automatically saved (in order to update the join table).
  • If any of these saves fails due to validation errors, then the assignment statement returns false and the assignment itself is cancelled.
  • If the parent object (the one declaring the has_and_belongs_to_many association) is unsaved (that is, new_record? returns true) then the child objects are not saved when they are added.
  • If you want to assign an object to a has_and_belongs_to_many association without saving the object, use the collection.build method.
  • Normal callbacks hook into the life cycle of Active Record objects, allowing you to work with those objects at various points
  • define association callbacks by adding options to the association declaration
  • Rails passes the object being added or removed to the callback.
  • stack callbacks on a single event by passing them as an array
  • If a before_add callback throws an exception, the object does not get added to the collection.
  • if a before_remove callback throws an exception, the object does not get removed from the collection
  • extend these objects through anonymous modules, adding new finders, creators, or other methods.
  • order_number
  • use a named extension module
  • proxy_association.owner returns the object that the association is a part of.
張 旭

Helm | - 0 views

helm.sh/developing_charts

helm kubernetes chart development devops package

shared by 張 旭 on 05 Aug 19 - No Cached
  • A chart is a collection of files that describe a related set of Kubernetes resources.
  • A single chart might be used to deploy something simple, like a memcached pod, or something complex, like a full web app stack with HTTP servers, databases, caches, and so on.
  • Charts are created as files laid out in a particular directory tree, then they can be packaged into versioned archives to be deployed.
  • ...170 more annotations...
  • A chart is organized as a collection of files inside of a directory.
  • values.yaml # The default configuration values for this chart
  • charts/ # A directory containing any charts upon which this chart depends.
  • templates/ # A directory of templates that, when combined with values, # will generate valid Kubernetes manifest files.
  • version: A SemVer 2 version (required)
  • apiVersion: The chart API version, always "v1" (required)
  • Every chart must have a version number. A version must follow the SemVer 2 standard.
  • non-SemVer names are explicitly disallowed by the system.
  • When generating a package, the helm package command will use the version that it finds in the Chart.yaml as a token in the package name.
  • the appVersion field is not related to the version field. It is a way of specifying the version of the application.
  • appVersion: The version of the app that this contains (optional). This needn't be SemVer.
  • If the latest version of a chart in the repository is marked as deprecated, then the chart as a whole is considered to be deprecated.
  • deprecated: Whether this chart is deprecated (optional, boolean)
  • one chart may depend on any number of other charts.
  • dependencies can be dynamically linked through the requirements.yaml file or brought in to the charts/ directory and managed manually.
  • the preferred method of declaring dependencies is by using a requirements.yaml file inside of your chart.
  • A requirements.yaml file is a simple file for listing your dependencies.
  • The repository field is the full URL to the chart repository.
  • you must also use helm repo add to add that repo locally.
  • helm dependency update and it will use your dependency file to download all the specified charts into your charts/ directory for you.
  • When helm dependency update retrieves charts, it will store them as chart archives in the charts/ directory.
  • Managing charts with requirements.yaml is a good way to easily keep charts updated, and also share requirements information throughout a team.
  • All charts are loaded by default.
  • The condition field holds one or more YAML paths (delimited by commas). If this path exists in the top parent’s values and resolves to a boolean value, the chart will be enabled or disabled based on that boolean value.
  • The tags field is a YAML list of labels to associate with this chart.
  • all charts with tags can be enabled or disabled by specifying the tag and a boolean value.
  • The --set parameter can be used as usual to alter tag and condition values.
  • Conditions (when set in values) always override tags.
  • The first condition path that exists wins and subsequent ones for that chart are ignored.
  • The keys containing the values to be imported can be specified in the parent chart’s requirements.yaml file using a YAML list. Each item in the list is a key which is imported from the child chart’s exports field.
  • specifying the key data in our import list, Helm looks in the exports field of the child chart for data key and imports its contents.
  • the parent key data is not contained in the parent’s final values. If you need to specify the parent key, use the ‘child-parent’ format.
  • To access values that are not contained in the exports key of the child chart’s values, you will need to specify the source key of the values to be imported (child) and the destination path in the parent chart’s values (parent).
  • To drop a dependency into your charts/ directory, use the helm fetch command
  • A dependency can be either a chart archive (foo-1.2.3.tgz) or an unpacked chart directory.
  • name cannot start with _ or .. Such files are ignored by the chart loader.
  • a single release is created with all the objects for the chart and its dependencies.
  • Helm Chart templates are written in the Go template language, with the addition of 50 or so add-on template functions from the Sprig library and a few other specialized functions
  • When Helm renders the charts, it will pass every file in that directory through the template engine.
  • Chart developers may supply a file called values.yaml inside of a chart. This file can contain default values.
  • Chart users may supply a YAML file that contains values. This can be provided on the command line with helm install.
  • When a user supplies custom values, these values will override the values in the chart’s values.yaml file.
  • Template files follow the standard conventions for writing Go templates
  • {{default "minio" .Values.storage}}
  • Values that are supplied via a values.yaml file (or via the --set flag) are accessible from the .Values object in a template.
  • pre-defined, are available to every template, and cannot be overridden
  • the names are case sensitive
  • Release.Name: The name of the release (not the chart)
  • Release.IsUpgrade: This is set to true if the current operation is an upgrade or rollback.
  • Release.Revision: The revision number. It begins at 1, and increments with each helm upgrade
  • Chart: The contents of the Chart.yaml
  • Files: A map-like object containing all non-special files in the chart.
  • Files can be accessed using {{index .Files "file.name"}} or using the {{.Files.Get name}} or {{.Files.GetString name}} functions.
  • .helmignore
  • access the contents of the file as []byte using {{.Files.GetBytes}}
  • Any unknown Chart.yaml fields will be dropped
  • Chart.yaml cannot be used to pass arbitrarily structured data into the template.
  • A values file is formatted in YAML.
  • A chart may include a default values.yaml file
  • be merged into the default values file.
  • The default values file included inside of a chart must be named values.yaml
  • accessible inside of templates using the .Values object
  • Values files can declare values for the top-level chart, as well as for any of the charts that are included in that chart’s charts/ directory.
  • Charts at a higher level have access to all of the variables defined beneath.
  • lower level charts cannot access things in parent charts
  • Values are namespaced, but namespaces are pruned.
  • the scope of the values has been reduced and the namespace prefix removed
  • Helm supports special “global” value.
  • a way of sharing one top-level variable with all subcharts, which is useful for things like setting metadata properties like labels.
  • If a subchart declares a global variable, that global will be passed downward (to the subchart’s subcharts), but not upward to the parent chart.
  • global variables of parent charts take precedence over the global variables from subcharts.
  • helm lint
  • A chart repository is an HTTP server that houses one or more packaged charts
  • Any HTTP server that can serve YAML files and tar files and can answer GET requests can be used as a repository server.
  • Helm does not provide tools for uploading charts to remote repository servers.
  • the only way to add a chart to $HELM_HOME/starters is to manually copy it there.
  • Helm provides a hook mechanism to allow chart developers to intervene at certain points in a release’s life cycle.
  • Execute a Job to back up a database before installing a new chart, and then execute a second job after the upgrade in order to restore data.
  • Hooks are declared as an annotation in the metadata section of a manifest
  • Hooks work like regular templates, but they have special annotations
  • pre-install
  • post-install: Executes after all resources are loaded into Kubernetes
  • pre-delete
  • post-delete: Executes on a deletion request after all of the release’s resources have been deleted.
  • pre-upgrade
  • post-upgrade
  • pre-rollback
  • post-rollback: Executes on a rollback request after all resources have been modified.
  • crd-install
  • test-success: Executes when running helm test and expects the pod to return successfully (return code == 0).
  • test-failure: Executes when running helm test and expects the pod to fail (return code != 0).
  • Hooks allow you, the chart developer, an opportunity to perform operations at strategic points in a release lifecycle
  • Tiller then loads the hook with the lowest weight first (negative to positive)
  • Tiller returns the release name (and other data) to the client
  • If the resources is a Job kind, Tiller will wait until the job successfully runs to completion.
  • if the job fails, the release will fail. This is a blocking operation, so the Helm client will pause while the Job is run.
  • If they have hook weights (see below), they are executed in weighted order. Otherwise, ordering is not guaranteed.
  • good practice to add a hook weight, and set it to 0 if weight is not important.
  • The resources that a hook creates are not tracked or managed as part of the release.
  • leave the hook resource alone.
  • To destroy such resources, you need to either write code to perform this operation in a pre-delete or post-delete hook or add "helm.sh/hook-delete-policy" annotation to the hook template file.
  • Hooks are just Kubernetes manifest files with special annotations in the metadata section
  • One resource can implement multiple hooks
  • no limit to the number of different resources that may implement a given hook.
  • When subcharts declare hooks, those are also evaluated. There is no way for a top-level chart to disable the hooks declared by subcharts.
  • Hook weights can be positive or negative numbers but must be represented as strings.
  • sort those hooks in ascending order.
  • Hook deletion policies
  • "before-hook-creation" specifies Tiller should delete the previous hook before the new hook is launched.
  • By default Tiller will wait for 60 seconds for a deleted hook to no longer exist in the API server before timing out.
  • Custom Resource Definitions (CRDs) are a special kind in Kubernetes.
  • The crd-install hook is executed very early during an installation, before the rest of the manifests are verified.
  • A common reason why the hook resource might already exist is that it was not deleted following use on a previous install/upgrade.
  • Helm uses Go templates for templating your resource files.
  • two special template functions: include and required
  • include function allows you to bring in another template, and then pass the results to other template functions.
  • The required function allows you to declare a particular values entry as required for template rendering.
  • If the value is empty, the template rendering will fail with a user submitted error message.
  • When you are working with string data, you are always safer quoting the strings than leaving them as bare words
  • Quote Strings, Don’t Quote Integers
  • when working with integers do not quote the values
  • env variables values which are expected to be string
  • to include a template, and then perform an operation on that template’s output, Helm has a special include function
  • The above includes a template called toYaml, passes it $value, and then passes the output of that template to the nindent function.
  • Go provides a way for setting template options to control behavior when a map is indexed with a key that’s not present in the map
  • The required function gives developers the ability to declare a value entry as required for template rendering.
  • The tpl function allows developers to evaluate strings as templates inside a template.
  • Rendering a external configuration file
  • (.Files.Get "conf/app.conf")
  • Image pull secrets are essentially a combination of registry, username, and password.
  • Automatically Roll Deployments When ConfigMaps or Secrets change
  • configmaps or secrets are injected as configuration files in containers
  • a restart may be required should those be updated with a subsequent helm upgrade
  • The sha256sum function can be used to ensure a deployment’s annotation section is updated if another file changes
  • checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}
  • helm upgrade --recreate-pods
  • "helm.sh/resource-policy": keep
  • resources that should not be deleted when Helm runs a helm delete
  • this resource becomes orphaned. Helm will no longer manage it in any way.
  • create some reusable parts in your chart
  • In the templates/ directory, any file that begins with an underscore(_) is not expected to output a Kubernetes manifest file.
  • by convention, helper templates and partials are placed in a _helpers.tpl file.
  • The current best practice for composing a complex application from discrete parts is to create a top-level umbrella chart that exposes the global configurations, and then use the charts/ subdirectory to embed each of the components.
  • SAP’s Converged charts: These charts install SAP Converged Cloud a full OpenStack IaaS on Kubernetes. All of the charts are collected together in one GitHub repository, except for a few submodules.
  • Deis’s Workflow: This chart exposes the entire Deis PaaS system with one chart. But it’s different from the SAP chart in that this umbrella chart is built from each component, and each component is tracked in a different Git repository.
  • YAML is a superset of JSON
  • any valid JSON structure ought to be valid in YAML.
  • As a best practice, templates should follow a YAML-like syntax unless the JSON syntax substantially reduces the risk of a formatting issue.
  • There are functions in Helm that allow you to generate random data, cryptographic keys, and so on.
  • a chart repository is a location where packaged charts can be stored and shared.
  • A chart repository is an HTTP server that houses an index.yaml file and optionally some packaged charts.
  • Because a chart repository can be any HTTP server that can serve YAML and tar files and can answer GET requests, you have a plethora of options when it comes down to hosting your own chart repository.
  • It is not required that a chart package be located on the same server as the index.yaml file.
  • A valid chart repository must have an index file. The index file contains information about each chart in the chart repository.
  • The Helm project provides an open-source Helm repository server called ChartMuseum that you can host yourself.
  • $ helm repo index fantastic-charts --url https://fantastic-charts.storage.googleapis.com
  • A repository will not be added if it does not contain a valid index.yaml
  • add the repository to their helm client via the helm repo add [NAME] [URL] command with any name they would like to use to reference the repository.
  • Helm has provenance tools which help chart users verify the integrity and origin of a package.
  • Integrity is established by comparing a chart to a provenance record
  • The provenance file contains a chart’s YAML file plus several pieces of verification information
  • Chart repositories serve as a centralized collection of Helm charts.
  • Chart repositories must make it possible to serve provenance files over HTTP via a specific request, and must make them available at the same URI path as the chart.
  • We don’t want to be “the certificate authority” for all chart signers. Instead, we strongly favor a decentralized model, which is part of the reason we chose OpenPGP as our foundational technology.
  • The Keybase platform provides a public centralized repository for trust information.
  • A chart contains a number of Kubernetes resources and components that work together.
  • A test in a helm chart lives under the templates/ directory and is a pod definition that specifies a container with a given command to run.
  • The pod definition must contain one of the helm test hook annotations: helm.sh/hook: test-success or helm.sh/hook: test-failure
  • helm test
  • nest your test suite under a tests/ directory like <chart-name>/templates/tests/
張 旭

Active Record Validations - Ruby on Rails Guides - 0 views

guides.rubyonrails.org/active_record_validations.html

rails validation database

shared by 張 旭 on 12 Apr 16 - No Cached
  • validates :name, presence: true
  • Validations are used to ensure that only valid data is saved into your database
  • Model-level validations are the best way to ensure that only valid data is saved into your database.
  • ...117 more annotations...
  • native database constraints
  • client-side validations
  • controller-level validations
  • Database constraints and/or stored procedures make the validation mechanisms database-dependent and can make testing and maintenance more difficult
  • Client-side validations can be useful, but are generally unreliable
  • combined with other techniques, client-side validation can be a convenient way to provide users with immediate feedback
  • it's a good idea to keep your controllers skinny
  • model-level validations are the most appropriate in most circumstances.
  • Active Record uses the new_record? instance method to determine whether an object is already in the database or not.
  • Creating and saving a new record will send an SQL INSERT operation to the database. Updating an existing record will send an SQL UPDATE operation instead. Validations are typically run before these commands are sent to the database
  • The bang versions (e.g. save!) raise an exception if the record is invalid.
  • save and update return false
  • create just returns the object
  • skip validations, and will save the object to the database regardless of its validity.
  • be used with caution
  • update_all
  • save also has the ability to skip validations if passed validate: false as argument.
  • save(validate: false)
  • valid? triggers your validations and returns true if no errors
  • After Active Record has performed validations, any errors found can be accessed through the errors.messages instance method
  • By definition, an object is valid if this collection is empty after running validations.
  • validations are not run when using new.
  • invalid? is simply the inverse of valid?.
  • To verify whether or not a particular attribute of an object is valid, you can use errors[:attribute]. I
  • only useful after validations have been run
  • Every time a validation fails, an error message is added to the object's errors collection,
  • All of them accept the :on and :message options, which define when the validation should be run and what message should be added to the errors collection if it fails, respectively.
  • validates that a checkbox on the user interface was checked when a form was submitted.
  • agree to your application's terms of service
  • 'acceptance' does not need to be recorded anywhere in your database (if you don't have a field for it, the helper will just create a virtual attribute).
  • It defaults to "1" and can be easily changed.
  • use this helper when your model has associations with other models and they also need to be validated
  • valid? will be called upon each one of the associated objects.
  • work with all of the association types
  • Don't use validates_associated on both ends of your associations.
    • 張 旭
      張 旭 on 12 Apr 16
       
      關聯式的物件驗證，在其中一方啟動就好了！
  • each associated object will contain its own errors collection
  • errors do not bubble up to the calling model
  • when you have two text fields that should receive exactly the same content
  • This validation creates a virtual attribute whose name is the name of the field that has to be confirmed with "_confirmation" appended.
  • To require confirmation, make sure to add a presence check for the confirmation attribute
  • this set can be any enumerable object.
  • The exclusion helper has an option :in that receives the set of values that will not be accepted for the validated attributes.
  • :in option has an alias called :within
  • validates the attributes' values by testing whether they match a given regular expression, which is specified using the :with option.
  • attribute does not match the regular expression by using the :without option.
  • validates that the attributes' values are included in a given set
  • :in option has an alias called :within
  • specify length constraints
  • :minimum
  • :maximum
  • :in (or :within)
  • :is - The attribute length must be equal to the given value.
  • :wrong_length, :too_long, and :too_short options and %{count} as a placeholder for the number corresponding to the length constraint being used.
  • split the value in a different way using the :tokenizer option:
    • 張 旭
      張 旭 on 12 Apr 16
       
      自己提供切割算字數的方式
  • validates that your attributes have only numeric values
  • By default, it will match an optional sign followed by an integral or floating point number.
  • set :only_integer to true.
  • allows a trailing newline character.
  • :greater_than
  • :greater_than_or_equal_to
  • :equal_to
  • :less_than
  • :less_than_or_equal_to
  • :odd - Specifies the value must be an odd number if set to true.
  • :even - Specifies the value must be an even number if set to true.
  • validates that the specified attributes are not empty
  • if the value is either nil or a blank string
  • validate associated records whose presence is required, you must specify the :inverse_of option for the association
  • inverse_of
  • an association is present, you'll need to test whether the associated object itself is present, and not the foreign key used to map the association
  • false.blank? is true
  • validate the presence of a boolean field
  • ensure the value will NOT be nil
  • validates that the specified attributes are absent
  • not either nil or a blank string
  • be sure that an association is absent
  • false.present? is false
  • validate the absence of a boolean field you should use validates :field_name, exclusion: { in: [true, false] }.
  • validates that the attribute's value is unique right before the object gets saved
  • a :scope option that you can use to specify other attributes that are used to limit the uniqueness check
  • a :case_sensitive option that you can use to define whether the uniqueness constraint will be case sensitive or not.
  • There is no default error message for validates_with.
  • To implement the validate method, you must have a record parameter defined, which is the record to be validated.
  • the validator will be initialized only once for the whole application life cycle, and not on each validation run, so be careful about using instance variables inside it.
  • passes the record to a separate class for validation
  • use a plain old Ruby object
  • validates attributes against a block
  • The block receives the record, the attribute's name and the attribute's value. You can do anything you like to check for valid data within the block
  • will let validation pass if the attribute's value is blank?, like nil or an empty string
  • the :message option lets you specify the message that will be added to the errors collection when validation fails
  • skips the validation when the value being validated is nil
  • specify when the validation should happen
  • raise ActiveModel::StrictValidationFailed when the object is invalid
  • You can do that by using the :if and :unless options, which can take a symbol, a string, a Proc or an Array.
  • use the :if option when you want to specify when the validation should happen
  • using eval and needs to contain valid Ruby code.
  • Using a Proc object gives you the ability to write an inline condition instead of a separate method
  • have multiple validations use one condition, it can be easily achieved using with_options.
  • implement a validate method which takes a record as an argument and performs the validation on it
  • validates_with method
  • implement a validate_each method which takes three arguments: record, attribute, and value
  • combine standard validations with your own custom validators.
  • :expiration_date_cannot_be_in_the_past,    :discount_cannot_be_greater_than_total_value
  • By default such validations will run every time you call valid?
  • errors[] is used when you want to check the error messages for a specific attribute.
  • Returns an instance of the class ActiveModel::Errors containing all errors.
  • lets you manually add messages that are related to particular attributes
  • using []= setter
  • errors[:base] is an array, you can simply add a string to it and it will be used as an error message.
  • use this method when you want to say that the object is invalid, no matter the values of its attributes.
  • clear all the messages in the errors collection
  • calling errors.clear upon an invalid object won't actually make it valid: the errors collection will now be empty, but the next time you call valid? or any method that tries to save this object to the database, the validations will run again.
  • the total number of error messages for the object.
  • .errors.full_messages.each
  • .field_with_errors
張 旭

Rails Routing from the Outside In - Ruby on Rails Guides - 0 views

guides.rubyonrails.org/routing.html

rails router path url namespace

shared by 張 旭 on 09 Mar 14 - Cached
  • Resource routing allows you to quickly declare all of the common routes for a given resourceful controller.
  • Rails would dispatch that request to the destroy method on the photos controller with { id: '17' } in params.
  • a resourceful route provides a mapping between HTTP verbs and URLs to controller actions.
  • ...86 more annotations...
  • each action also maps to particular CRUD operations in a database
  • resource :photo and resources :photos creates both singular and plural routes that map to the same controller (PhotosController).
  • One way to avoid deep nesting (as recommended above) is to generate the collection actions scoped under the parent, so as to get a sense of the hierarchy, but to not nest the member actions.
  • to only build routes with the minimal amount of information to uniquely identify the resource
  • The shallow method of the DSL creates a scope inside of which every nesting is shallow
  • These concerns can be used in resources to avoid code duplication and share behavior across routes
  • add a member route, just add a member block into the resource block
  • You can leave out the :on option, this will create the same member route except that the resource id value will be available in params[:photo_id] instead of params[:id].
  • Singular Resources
  • use a singular resource to map /profile (rather than /profile/:id) to the show action
  • Passing a String to get will expect a controller#action format
  • workaround
  • organize groups of controllers under a namespace
  • route /articles (without the prefix /admin) to Admin::ArticlesController
  • route /admin/articles to ArticlesController (without the Admin:: module prefix)
  • Nested routes allow you to capture this relationship in your routing.
  • helpers take an instance of Magazine as the first parameter (magazine_ads_url(@magazine)).
  • Resources should never be nested more than 1 level deep.
  • via the :shallow option
  • a balance between descriptive routes and deep nesting
  • :shallow_path prefixes member paths with the specified parameter
  • Routing Concerns allows you to declare common routes that can be reused inside other resources and routes
  • Rails can also create paths and URLs from an array of parameters.
  • use url_for with a set of objects
  • In helpers like link_to, you can specify just the object in place of the full url_for call
  • insert the action name as the first element of the array
  • This will recognize /photos/1/preview with GET, and route to the preview action of PhotosController, with the resource id value passed in params[:id]. It will also create the preview_photo_url and preview_photo_path helpers.
  • pass :on to a route, eliminating the block:
  • Collection Routes
  • This will enable Rails to recognize paths such as /photos/search with GET, and route to the search action of PhotosController. It will also create the search_photos_url and search_photos_path route helpers.
  • simple routing makes it very easy to map legacy URLs to new Rails actions
  • add an alternate new action using the :on shortcut
  • When you set up a regular route, you supply a series of symbols that Rails maps to parts of an incoming HTTP request.
  • :controller maps to the name of a controller in your application
  • :action maps to the name of an action within that controller
  • optional parameters, denoted by parentheses
  • This route will also route the incoming request of /photos to PhotosController#index, since :action and :id are
  • use a constraint on :controller that matches the namespace you require
  • dynamic segments don't accept dots
  • The params will also include any parameters from the query string
  • :defaults option.
  • set params[:format] to "jpg"
  • cannot override defaults via query parameters
  • specify a name for any route using the :as option
  • create logout_path and logout_url as named helpers in your application.
  • Inside the show action of UsersController, params[:username] will contain the username for the user.
  • should use the get, post, put, patch and delete methods to constrain a route to a particular verb.
  • use the match method with the :via option to match multiple verbs at once
  • Routing both GET and POST requests to a single action has security implications
  • 'GET' in Rails won't check for CSRF token. You should never write to the database from 'GET' requests
  • use the :constraints option to enforce a format for a dynamic segment
  • constraints
  • don't need to use anchors
  • Request-Based Constraints
  • the same name as the hash key and then compare the return value with the hash value.
  • constraint values should match the corresponding Request object method return type
    • 張 旭
      張 旭 on 11 Apr 16
       
      應該就是檢查來源的 request， 如果是某個特定的 request 來訪問的，就通過。
  • blacklist
    • 張 旭
      張 旭 on 11 Apr 16
       
      這裡有點複雜 ...
  • redirect helper
  • reuse dynamic segments from the match in the path to redirect
  • this redirection is a 301 "Moved Permanently" redirect.
  • root method
  • put the root route at the top of the file
  • The root route only routes GET requests to the action.
  • root inside namespaces and scopes
  • For namespaced controllers you can use the directory notation
  • Only the directory notation is supported
  • use the :constraints option to specify a required format on the implicit id
  • specify a single constraint to apply to a number of routes by using the block
  • non-resourceful routes
  • :id parameter doesn't accept dots
  • :as option lets you override the normal naming for the named route helpers
  • use the :as option to prefix the named route helpers that Rails generates for a rout
  • prevent name collisions
  • prefix routes with a named parameter
  • This will provide you with URLs such as /bob/articles/1 and will allow you to reference the username part of the path as params[:username] in controllers, helpers and views
  • :only option
  • :except option
  • generate only the routes that you actually need can cut down on memory use and speed up the routing process.
  • alter path names
  • http://localhost:3000/rails/info/routes
  • rake routes
  • setting the CONTROLLER environment variable
  • Routes should be included in your testing strategy
  • assert_generates assert_recognizes assert_routing
張 旭

Helm | - 0 views

helm.sh/...chart_template_guide

helm kubernetes chart devops development

shared by 張 旭 on 06 Aug 19 - No Cached
  • Templates generate manifest files, which are YAML-formatted resource descriptions that Kubernetes can understand.
  • service.yaml: A basic manifest for creating a service endpoint for your deployment
  • In Kubernetes, a ConfigMap is simply a container for storing configuration data.
  • ...88 more annotations...
  • deployment.yaml: A basic manifest for creating a Kubernetes deployment
  • using the suffix .yaml for YAML files and .tpl for helpers.
  • It is just fine to put a plain YAML file like this in the templates/ directory.
  • helm get manifest
  • The helm get manifest command takes a release name (full-coral) and prints out all of the Kubernetes resources that were uploaded to the server. Each file begins with --- to indicate the start of a YAML document
  • Names should be unique to a release
  • The name: field is limited to 63 characters because of limitations to the DNS system.
  • release names are limited to 53 characters
  • {{ .Release.Name }}
  • A template directive is enclosed in {{ and }} blocks.
  • The values that are passed into a template can be thought of as namespaced objects, where a dot (.) separates each namespaced element.
  • The leading dot before Release indicates that we start with the top-most namespace for this scope
  • The Release object is one of the built-in objects for Helm
  • When you want to test the template rendering, but not actually install anything, you can use helm install ./mychart --debug --dry-run
  • Using --dry-run will make it easier to test your code, but it won’t ensure that Kubernetes itself will accept the templates you generate.
  • Objects are passed into a template from the template engine.
  • create new objects within your templates
  • Objects can be simple, and have just one value. Or they can contain other objects or functions.
  • Release is one of the top-level objects that you can access in your templates.
  • Release.Namespace: The namespace to be released into (if the manifest doesn’t override)
  • Values: Values passed into the template from the values.yaml file and from user-supplied files. By default, Values is empty.
  • Chart: The contents of the Chart.yaml file.
  • Files: This provides access to all non-special files in a chart.
  • Files.Get is a function for getting a file by name
  • Files.GetBytes is a function for getting the contents of a file as an array of bytes instead of as a string. This is useful for things like images.
  • Template: Contains information about the current template that is being executed
  • BasePath: The namespaced path to the templates directory of the current chart
  • The built-in values always begin with a capital letter.
  • Go’s naming convention
  • use only initial lower case letters in order to distinguish local names from those built-in.
  • If this is a subchart, the values.yaml file of a parent chart
  • Individual parameters passed with --set
  • values.yaml is the default, which can be overridden by a parent chart’s values.yaml, which can in turn be overridden by a user-supplied values file, which can in turn be overridden by --set parameters.
  • While structuring data this way is possible, the recommendation is that you keep your values trees shallow, favoring flatness.
  • If you need to delete a key from the default values, you may override the value of the key to be null, in which case Helm will remove the key from the overridden values merge.
  • Kubernetes would then fail because you can not declare more than one livenessProbe handler.
  • When injecting strings from the .Values object into the template, we ought to quote these strings.
  • quote
  • Template functions follow the syntax functionName arg1 arg2...
  • While we talk about the “Helm template language” as if it is Helm-specific, it is actually a combination of the Go template language, some extra functions, and a variety of wrappers to expose certain objects to the templates.
  • Drawing on a concept from UNIX, pipelines are a tool for chaining together a series of template commands to compactly express a series of transformations.
  • pipelines are an efficient way of getting several things done in sequence
  • The repeat function will echo the given string the given number of times
  • default DEFAULT_VALUE GIVEN_VALUE. This function allows you to specify a default value inside of the template, in case the value is omitted.
  • all static default values should live in the values.yaml, and should not be repeated using the default command
  • Operators are implemented as functions that return a boolean value.
  • To use eq, ne, lt, gt, and, or, not etcetera place the operator at the front of the statement followed by its parameters just as you would a function.
  • if and
  • if or
  • with to specify a scope
  • range, which provides a “for each”-style loop
  • block declares a special kind of fillable template area
  • A pipeline is evaluated as false if the value is: a boolean false a numeric zero an empty string a nil (empty or null) an empty collection (map, slice, tuple, dict, array)
  • incorrect YAML because of the whitespacing
  • When the template engine runs, it removes the contents inside of {{ and }}, but it leaves the remaining whitespace exactly as is.
  • {{- (with the dash and space added) indicates that whitespace should be chomped left, while -}} means whitespace to the right should be consumed.
  • Newlines are whitespace!
  • an * at the end of the line indicates a newline character that would be removed
  • Be careful with the chomping modifiers.
  • the indent function
  • Scopes can be changed. with can allow you to set the current scope (.) to a particular object.
  • Inside of the restricted scope, you will not be able to access the other objects from the parent scope.
  • range
  • The range function will “range over” (iterate through) the pizzaToppings list.
  • Just like with sets the scope of ., so does a range operator.
  • The toppings: |- line is declaring a multi-line string.
  • not a YAML list. It’s a big string.
  • the data in ConfigMaps data is composed of key/value pairs, where both the key and the value are simple strings.
  • The |- marker in YAML takes a multi-line string.
  • range can be used to iterate over collections that have a key and a value (like a map or dict).
  • In Helm templates, a variable is a named reference to another object. It follows the form $name
  • Variables are assigned with a special assignment operator: :=
  • {{- $relname := .Release.Name -}}
  • capture both the index and the value
  • the integer index (starting from zero) to $index and the value to $topping
  • For data structures that have both a key and a value, we can use range to get both
  • Variables are normally not “global”. They are scoped to the block in which they are declared.
  • one variable that is always global - $ - this variable will always point to the root context.
  • $.
  • $.
  • Helm template language is its ability to declare multiple templates and use them together.
  • A named template (sometimes called a partial or a subtemplate) is simply a template defined inside of a file, and given a name.
  • when naming templates: template names are global.
  • If you declare two templates with the same name, whichever one is loaded last will be the one used.
  • you should be careful to name your templates with chart-specific names.
  • templates in subcharts are compiled together with top-level templates
  • naming convention is to prefix each defined template with the name of the chart: {{ define "mychart.labels" }}
  • Helm has over 60 available functions.
張 旭

Active Record Migrations - Ruby on Rails Guides - 0 views

edgeguides.rubyonrails.org/active_record_migrations.html

rails database model migration

shared by 張 旭 on 12 Apr 16 - No Cached
    • 張 旭
      張 旭 on 12 Apr 16
       
       跟 belongs_to 與 has_many 設定對應的 Migrattion
    • 張 旭
      張 旭 on 12 Apr 16
       
      has_and_belongs_to_many 的對應？
  • add_column and remove_column
  • ...114 more annotations...
  • allowing your schema and changes to be database independent.
  • each migration as being a new 'version' of the database
  • each migration modifies it to add or remove tables, columns, or entries
  • Active Record will also update your db/schema.rb file to match the up-to-date structure of your database.
  • A primary key column called id will also be added implicitly, as it's the default primary key for all Active Record models
  • roll this migration back, it will remove the table
  • timestamps macro adds two columns, created_at and updated_at
  • On databases that support transactions with statements that change the schema, migrations are wrapped in a transaction
  • reversible
  • use up and down instead of change
  • Migrations are stored as files in the db/migrate directory, one for each migration class.
  • a UTC timestamp identifying
  • Rails uses this timestamp to determine which migration should be run and in what order
  • "AddXXXToYYY" or "RemoveXXXFromYYY"
  • use a Ruby DSL
  • column type as references
  • part_number:string:index
  • a migration to remove a column
  • "CreateXXX"
  • change_column_null
  • AddUserRefToProducts
  • :references
  • produce join tables if JoinTable is part of the name
  • CreateJoinTable
  • The model and scaffold generators will create migrations appropriate for adding a new model.
  • enclosed by curly braces and follow the field type
  • create_table
  • By default, create_table will create a primary key called id
  • add an index on the new column
  • when using MySQL, the default is ENGINE=InnoDB
  • create_join_table creates an HABTM (has and belongs to many) join table
  • To customize the name of the table, provide a :table_name option:
  • create_join_table also accepts a block
  • change_table, used for changing existing tables
  • remove
  • rename
  • add_column
  • change_column
  • remove_column
  • change_column_default
  • place an SQL fragment in the :options option.
  • limit
  • precision
  • scale
  • polymorphic
  • default
  • index
  • add_foreign_key
  • Active Record only supports single column foreign keys.
  • use the old style of migration using up and down methods instead of the change method.
  • .connection.execute
  • change_table is also reversible, as long as the block does not call change, change_default or remove.
  • remove_column is reversible if you supply the column type as the third argument
  • Complex migrations may require processing that Active Record doesn't know how to reverse
  • reversible
  • Using reversible will ensure that the instructions are executed in the right order too.
  • add_column add_foreign_key add_index add_reference add_timestamps change_column_default (must supply a :from and :to option) change_column_null create_join_table create_table disable_extension drop_join_table drop_table (must supply a block) enable_extension remove_column (must supply a type) remove_foreign_key (must supply a second table) remove_index remove_reference remove_timestamps rename_column rename_index rename_table
  • :column_options option
  • have the option :null set to false by default
  • By default, the name of the join table comes from the union of the first two arguments provided to create_join_table
  • in alphabetical order
  • change_column command is irreversible.
    • 張 旭
      張 旭 on 12 Apr 16
       
      關聯物在前，被關聯物在後。 A 關聯到 B
  • If the column names can not be derived from the table names, you can use the :column and :primary_key options.
  • figure out the column name
  • foreign key for a specific column
  • foreign key by name
    • 張 旭
      張 旭 on 12 Apr 16
       
      不懂 column 跟 name 的用法差異，基本上一樣。
  • Active Record knows how to reverse the migration automatically
    • 張 旭
      張 旭 on 12 Apr 16
       
      使用內建的 method，Rails 比較容易自動 rollback
    • 張 旭
      張 旭 on 12 Apr 16
       
      除了幾個特殊的 change_ 跟 remove_
  • should use reversible or write the up and down methods instead of using the change method
  • If your migration is irreversible, you should raise ActiveRecord::IrreversibleMigration from your down method.
  • DontUseConstraintForZipcodeValidationMigration
  • rails db:migrate
  • the db:migrate task also invokes the db:schema:dump task, which will update your db/schema.rb file to match the structure of your database.
  • specify a target version
  • all migrations up to and including 20080906120000
  • run the down method on all the migrations down to, but not including, 20080906120000
  • rails db:rollback
  • db:migrate:redo task is a shortcut for doing a rollback and then migrating back up again
    • 張 旭
      張 旭 on 12 Apr 16
       
      舊版的還是 rake！
  • STEP parameter
  • db:setup task will create the database, load the schema and initialize it with the seed data
  • db:reset task will drop the database and set it up again. This is functionally equivalent to rails db:drop db:setup.
  • run a specific migration up or down, the db:migrate:up and db:migrate:down
  • the RAILS_ENV environment variable
  • db:migrate VERBOSE=false will suppress all output.
  • If you have already run the migration, then you cannot just edit the migration and run the migration again: Rails thinks it has already run the migration and so will do nothing when you run rails db:migrate.
  • must rollback the migration (for example with bin/rails db:rollback), edit your migration and then run rails db:migrate to run the corrected version.
  • editing existing migrations is not a good idea.
  • should write a new migration that performs the changes you require
  • revert method can be helpful when writing a new migration to undo previous migrations in whole or in part
  • require_relative
  • revert
  • They are not designed to be edited, they just represent the current state of the database.
  • Schema Files for
  • Schema files are also useful if you want a quick look at what attributes an Active Record object has
  • annotate_models gem automatically adds and updates comments at the top of each model summarizing the schema if you desire that functionality.
  • database-independent
  • multiple databases
  • db/schema.rb cannot express database specific items such as triggers, stored procedures or check constraints
  • you can execute custom SQL statements, the schema dumper cannot reconstitute those statements from the database
  • db:structure:dump
    • 張 旭
      張 旭 on 12 Apr 16
       
      資料庫種類不相依的 schema 付出的代價就是有些特殊的資料庫特性無法描述出來，例如 trigger；如果有在 migration 寫 SQL 的，簡單說 schema dumper 這邊就要設定成 :sql 而不是預設的 :ruby
  • set in config/application.rb by the config.active_record.schema_format setting, which may be either :sql or :ruby.
  • check them into source control.
  • db/schema.rb contains the current version number of the database
  • Validations such as validates :foreign_key, uniqueness: true are one way in which models can enforce data integrity
  • The :dependent option on associations allows models to automatically destroy child objects when the parent is destroyed.
  • Migrations can also be used to add or modify data
  • Initial
  • To add initial data after a database is created, Rails has a built-in 'seeds' feature that makes the process quick and easy.
  • db/seeds.rb
  • rails db:seed
張 旭

Volumes - Kubernetes - 0 views

kubernetes.io/...volumes

kubernetes volume disk nfs

shared by 張 旭 on 28 May 19 - No Cached
  • On-disk files in a Container are ephemeral,
  • when a Container crashes, kubelet will restart it, but the files will be lost - the Container starts with a clean state
  • In Docker, a volume is simply a directory on disk or in another Container.
  • ...105 more annotations...
  • A Kubernetes volume, on the other hand, has an explicit lifetime - the same as the Pod that encloses it.
  • a volume outlives any Containers that run within the Pod, and data is preserved across Container restarts.
    • 張 旭
      張 旭 on 06 Jul 19
       
      Kubernetes Volume 是跟著 Pod 的生命週期在走
  • Kubernetes supports many types of volumes, and a Pod can use any number of them simultaneously.
  • To use a volume, a Pod specifies what volumes to provide for the Pod (the .spec.volumes field) and where to mount those into Containers (the .spec.containers.volumeMounts field).
  • A process in a container sees a filesystem view composed from their Docker image and volumes.
  • Volumes can not mount onto other volumes or have hard links to other volumes.
  • Each Container in the Pod must independently specify where to mount each volume
  • localnfs
  • cephfs
  • awsElasticBlockStore
  • glusterfs
  • vsphereVolume
  • An awsElasticBlockStore volume mounts an Amazon Web Services (AWS) EBS Volume into your Pod.
  • the contents of an EBS volume are preserved and the volume is merely unmounted.
  • an EBS volume can be pre-populated with data, and that data can be “handed off” between Pods.
  • create an EBS volume using aws ec2 create-volume
  • the nodes on which Pods are running must be AWS EC2 instances
  • EBS only supports a single EC2 instance mounting a volume
  • check that the size and EBS volume type are suitable for your use!
  • A cephfs volume allows an existing CephFS volume to be mounted into your Pod.
  • the contents of a cephfs volume are preserved and the volume is merely unmounted.
    • 張 旭
      張 旭 on 06 Jul 19
       
      相當於自己的 AWS EBS
  • CephFS can be mounted by multiple writers simultaneously.
  • have your own Ceph server running with the share exported
  • configMap
  • The configMap resource provides a way to inject configuration data into Pods
  • When referencing a configMap object, you can simply provide its name in the volume to reference it
  • volumeMounts: - name: config-vol mountPath: /etc/config volumes: - name: config-vol configMap: name: log-config items: - key: log_level path: log_level
  • create a ConfigMap before you can use it.
  • A Container using a ConfigMap as a subPath volume mount will not receive ConfigMap updates.
  • An emptyDir volume is first created when a Pod is assigned to a Node, and exists as long as that Pod is running on that node.
  • When a Pod is removed from a node for any reason, the data in the emptyDir is deleted forever.
  • By default, emptyDir volumes are stored on whatever medium is backing the node - that might be disk or SSD or network storage, depending on your environment.
  • you can set the emptyDir.medium field to "Memory" to tell Kubernetes to mount a tmpfs (RAM-backed filesystem)
  • volumeMounts: - mountPath: /cache name: cache-volume volumes: - name: cache-volume emptyDir: {}
  • An fc volume allows an existing fibre channel volume to be mounted in a Pod.
  • configure FC SAN Zoning to allocate and mask those LUNs (volumes) to the target WWNs beforehand so that Kubernetes hosts can access them.
  • Flocker is an open-source clustered Container data volume manager. It provides management and orchestration of data volumes backed by a variety of storage backends.
  • emptyDir
  • flocker
  • A flocker volume allows a Flocker dataset to be mounted into a Pod
  • have your own Flocker installation running
  • A gcePersistentDisk volume mounts a Google Compute Engine (GCE) Persistent Disk into your Pod.
  • Using a PD on a Pod controlled by a ReplicationController will fail unless the PD is read-only or the replica count is 0 or 1
  • A glusterfs volume allows a Glusterfs (an open source networked filesystem) volume to be mounted into your Pod.
  • have your own GlusterFS installation running
  • A hostPath volume mounts a file or directory from the host node’s filesystem into your Pod.
  • a powerful escape hatch for some applications
  • access to Docker internals; use a hostPath of /var/lib/docker
  • allowing a Pod to specify whether a given hostPath should exist prior to the Pod running, whether it should be created, and what it should exist as
  • specify a type for a hostPath volume
  • the files or directories created on the underlying hosts are only writable by root.
  • hostPath: # directory location on host path: /data # this field is optional type: Directory
  • An iscsi volume allows an existing iSCSI (SCSI over IP) volume to be mounted into your Pod.
  • have your own iSCSI server running
  • A feature of iSCSI is that it can be mounted as read-only by multiple consumers simultaneously.
  • A local volume represents a mounted local storage device such as a disk, partition or directory.
  • Local volumes can only be used as a statically created PersistentVolume.
  • Compared to hostPath volumes, local volumes can be used in a durable and portable manner without manually scheduling Pods to nodes, as the system is aware of the volume’s node constraints by looking at the node affinity on the PersistentVolume.
  • If a node becomes unhealthy, then the local volume will also become inaccessible, and a Pod using it will not be able to run.
  • PersistentVolume spec using a local volume and nodeAffinity
  • PersistentVolume nodeAffinity is required when using local volumes. It enables the Kubernetes scheduler to correctly schedule Pods using local volumes to the correct node.
  • PersistentVolume volumeMode can now be set to “Block” (instead of the default value “Filesystem”) to expose the local volume as a raw block device.
  • When using local volumes, it is recommended to create a StorageClass with volumeBindingMode set to WaitForFirstConsumer
  • An nfs volume allows an existing NFS (Network File System) share to be mounted into your Pod.
  • NFS can be mounted by multiple writers simultaneously.
  • have your own NFS server running with the share exported
  • A persistentVolumeClaim volume is used to mount a PersistentVolume into a Pod.
  • PersistentVolumes are a way for users to “claim” durable storage (such as a GCE PersistentDisk or an iSCSI volume) without knowing the details of the particular cloud environment.
  • A projected volume maps several existing volume sources into the same directory.
  • All sources are required to be in the same namespace as the Pod. For more details, see the all-in-one volume design document.
  • Each projected volume source is listed in the spec under sources
  • A Container using a projected volume source as a subPath volume mount will not receive updates for those volume sources.
  • RBD volumes can only be mounted by a single consumer in read-write mode - no simultaneous writers allowed
  • A secret volume is used to pass sensitive information, such as passwords, to Pods
  • store secrets in the Kubernetes API and mount them as files for use by Pods
  • secret volumes are backed by tmpfs (a RAM-backed filesystem) so they are never written to non-volatile storage.
  • create a secret in the Kubernetes API before you can use it
  • A Container using a Secret as a subPath volume mount will not receive Secret updates.
  • StorageOS runs as a Container within your Kubernetes environment, making local or attached storage accessible from any node within the Kubernetes cluster.
  • Data can be replicated to protect against node failure. Thin provisioning and compression can improve utilization and reduce cost.
  • StorageOS provides block storage to Containers, accessible via a file system.
  • A vsphereVolume is used to mount a vSphere VMDK Volume into your Pod.
  • supports both VMFS and VSAN datastore.
  • create VMDK using one of the following methods before using with Pod.
  • share one volume for multiple uses in a single Pod.
  • The volumeMounts.subPath property can be used to specify a sub-path inside the referenced volume instead of its root.
  • volumeMounts: - name: workdir1 mountPath: /logs subPathExpr: $(POD_NAME)
  • env: - name: POD_NAME valueFrom: fieldRef: apiVersion: v1 fieldPath: metadata.name
  • Use the subPathExpr field to construct subPath directory names from Downward API environment variables
  • enable the VolumeSubpathEnvExpansion feature gate
  • The subPath and subPathExpr properties are mutually exclusive.
  • There is no limit on how much space an emptyDir or hostPath volume can consume, and no isolation between Containers or between Pods.
  • emptyDir and hostPath volumes will be able to request a certain amount of space using a resource specification, and to select the type of media to use, for clusters that have several media types.
  • the Container Storage Interface (CSI) and Flexvolume. They enable storage vendors to create custom storage plugins without adding them to the Kubernetes repository.
  • all volume plugins (like volume types listed above) were “in-tree” meaning they were built, linked, compiled, and shipped with the core Kubernetes binaries and extend the core Kubernetes API.
  • Container Storage Interface (CSI) defines a standard interface for container orchestration systems (like Kubernetes) to expose arbitrary storage systems to their container workloads.
  • Once a CSI compatible volume driver is deployed on a Kubernetes cluster, users may use the csi volume type to attach, mount, etc. the volumes exposed by the CSI driver.
  • The csi volume type does not support direct reference from Pod and may only be referenced in a Pod via a PersistentVolumeClaim object.
  • This feature requires CSIInlineVolume feature gate to be enabled:--feature-gates=CSIInlineVolume=true
  • In-tree plugins that support CSI Migration and have a corresponding CSI driver implemented are listed in the “Types of Volumes” section above.
  • Mount propagation allows for sharing volumes mounted by a Container to other Containers in the same Pod, or even to other Pods on the same node.
  • Mount propagation of a volume is controlled by mountPropagation field in Container.volumeMounts.
  • HostToContainer - This volume mount will receive all subsequent mounts that are mounted to this volume or any of its subdirectories.
  • Bidirectional - This volume mount behaves the same the HostToContainer mount. In addition, all volume mounts created by the Container will be propagated back to the host and to all Containers of all Pods that use the same volume.
  • Edit your Docker’s systemd service file. Set MountFlags as follows:MountFlags=shared
張 旭

Auto DevOps | GitLab - 0 views

docs.gitlab.com/...index.html

gitlab auto devops CI deploy

shared by 張 旭 on 02 Aug 19 - No Cached
  • Auto DevOps provides pre-defined CI/CD configuration which allows you to automatically detect, build, test, deploy, and monitor your applications
  • Just push your code and GitLab takes care of everything else.
  • Auto DevOps will be automatically disabled on the first pipeline failure.
  • ...78 more annotations...
  • Your project will continue to use an alternative CI/CD configuration file if one is found
  • Auto DevOps works with any Kubernetes cluster;
  • using the Docker or Kubernetes executor, with privileged mode enabled.
  • Base domain (needed for Auto Review Apps and Auto Deploy)
  • Kubernetes (needed for Auto Review Apps, Auto Deploy, and Auto Monitoring)
  • Prometheus (needed for Auto Monitoring)
  • scrape your Kubernetes cluster.
  • project level as a variable: KUBE_INGRESS_BASE_DOMAIN
  • A wildcard DNS A record matching the base domain(s) is required
  • Once set up, all requests will hit the load balancer, which in turn will route them to the Kubernetes pods that run your application(s).
  • review/ (every environment starting with review/)
  • staging
  • production
  • need to define a separate KUBE_INGRESS_BASE_DOMAIN variable for all the above based on the environment.
  • Continuous deployment to production: Enables Auto Deploy with master branch directly deployed to production.
  • Continuous deployment to production using timed incremental rollout
  • Automatic deployment to staging, manual deployment to production
  • Auto Build creates a build of the application using an existing Dockerfile or Heroku buildpacks.
  • If a project’s repository contains a Dockerfile, Auto Build will use docker build to create a Docker image.
  • Each buildpack requires certain files to be in your project’s repository for Auto Build to successfully build your application.
  • Auto Test automatically runs the appropriate tests for your application using Herokuish and Heroku buildpacks by analyzing your project to detect the language and framework.
  • Auto Code Quality uses the Code Quality image to run static analysis and other code checks on the current code.
  • Static Application Security Testing (SAST) uses the SAST Docker image to run static analysis on the current code and checks for potential security issues.
  • Dependency Scanning uses the Dependency Scanning Docker image to run analysis on the project dependencies and checks for potential security issues.
  • License Management uses the License Management Docker image to search the project dependencies for their license.
  • Vulnerability Static Analysis for containers uses Clair to run static analysis on a Docker image and checks for potential security issues.
  • Review Apps are temporary application environments based on the branch’s code so developers, designers, QA, product managers, and other reviewers can actually see and interact with code changes as part of the review process. Auto Review Apps create a Review App for each branch. Auto Review Apps will deploy your app to your Kubernetes cluster only. When no cluster is available, no deployment will occur.
  • The Review App will have a unique URL based on the project ID, the branch or tag name, and a unique number, combined with the Auto DevOps base domain.
  • Review apps are deployed using the auto-deploy-app chart with Helm, which can be customized.
  • Your apps should not be manipulated outside of Helm (using Kubernetes directly).
  • Dynamic Application Security Testing (DAST) uses the popular open source tool OWASP ZAProxy to perform an analysis on the current code and checks for potential security issues.
  • Auto Browser Performance Testing utilizes the Sitespeed.io container to measure the performance of a web page.
  • add the paths to a file named .gitlab-urls.txt in the root directory, one per line.
  • After a branch or merge request is merged into the project’s default branch (usually master), Auto Deploy deploys the application to a production environment in the Kubernetes cluster, with a namespace based on the project name and unique project ID
  • Auto Deploy doesn’t include deployments to staging or canary by default, but the Auto DevOps template contains job definitions for these tasks if you want to enable them.
  • Apps are deployed using the auto-deploy-app chart with Helm.
  • For internal and private projects a GitLab Deploy Token will be automatically created, when Auto DevOps is enabled and the Auto DevOps settings are saved.
  • If the GitLab Deploy Token cannot be found, CI_REGISTRY_PASSWORD is used. Note that CI_REGISTRY_PASSWORD is only valid during deployment.
  • If present, DB_INITIALIZE will be run as a shell command within an application pod as a helm post-install hook.
  • a post-install hook means that if any deploy succeeds, DB_INITIALIZE will not be processed thereafter.
  • DB_MIGRATE will be run as a shell command within an application pod as a helm pre-upgrade hook.
    • 張 旭
      張 旭 on 02 Aug 19
       
      如果專案類型不同，就要去查 buildpacks 裡面如何叫用該指令，例如 laravel 的 migration
    • 張 旭
      張 旭 on 02 Aug 19
       
      如果是自己的 Dockerfile 建立起來的，看來就不用鳥 buildpacks 的作法
  • Once your application is deployed, Auto Monitoring makes it possible to monitor your application’s server and response metrics right out of the box.
  • annotate the NGINX Ingress deployment to be scraped by Prometheus using prometheus.io/scrape: "true" and prometheus.io/port: "10254"
  • If you are also using Auto Review Apps and Auto Deploy and choose to provide your own Dockerfile, make sure you expose your application to port 5000 as this is the port assumed by the default Helm chart.
  • While Auto DevOps provides great defaults to get you started, you can customize almost everything to fit your needs; from custom buildpacks, to Dockerfiles, Helm charts, or even copying the complete CI/CD configuration into your project to enable staging and canary deployments, and more.
  • If your project has a Dockerfile in the root of the project repo, Auto DevOps will build a Docker image based on the Dockerfile rather than using buildpacks.
  • Auto DevOps uses Helm to deploy your application to Kubernetes.
  • Bundled chart - If your project has a ./chart directory with a Chart.yaml file in it, Auto DevOps will detect the chart and use it instead of the default one.
  • Create a project variable AUTO_DEVOPS_CHART with the URL of a custom chart to use or create two project variables AUTO_DEVOPS_CHART_REPOSITORY with the URL of a custom chart repository and AUTO_DEVOPS_CHART with the path to the chart.
  • make use of the HELM_UPGRADE_EXTRA_ARGS environment variable to override the default values in the values.yaml file in the default Helm chart.
  • specify the use of a custom Helm chart per environment by scoping the environment variable to the desired environment.
    • 張 旭
      張 旭 on 02 Aug 19
       
      Auto DevOps 就是一套人家寫好好的傳便便的 .gitlab-ci.yml
  • Your additions will be merged with the Auto DevOps template using the behaviour described for include
  • copy and paste the contents of the Auto DevOps template into your project and edit this as needed.
  • In order to support applications that require a database, PostgreSQL is provisioned by default.
  • Set up the replica variables using a project variable and scale your application by just redeploying it!
  • You should not scale your application using Kubernetes directly.
  • Some applications need to define secret variables that are accessible by the deployed application.
  • Auto DevOps detects variables where the key starts with K8S_SECRET_ and make these prefixed variables available to the deployed application, as environment variables.
  • Auto DevOps pipelines will take your application secret variables to populate a Kubernetes secret.
  • Environment variables are generally considered immutable in a Kubernetes pod.
  • if you update an application secret without changing any code then manually create a new pipeline, you will find that any running application pods will not have the updated secrets.
  • Variables with multiline values are not currently supported
  • The normal behavior of Auto DevOps is to use Continuous Deployment, pushing automatically to the production environment every time a new pipeline is run on the default branch.
  • If STAGING_ENABLED is defined in your project (e.g., set STAGING_ENABLED to 1 as a CI/CD variable), then the application will be automatically deployed to a staging environment, and a production_manual job will be created for you when you’re ready to manually deploy to production.
  • If CANARY_ENABLED is defined in your project (e.g., set CANARY_ENABLED to 1 as a CI/CD variable) then two manual jobs will be created: canary which will deploy the application to the canary environment production_manual which is to be used by you when you’re ready to manually deploy to production.
  • If INCREMENTAL_ROLLOUT_MODE is set to manual in your project, then instead of the standard production job, 4 different manual jobs will be created: rollout 10% rollout 25% rollout 50% rollout 100%
  • The percentage is based on the REPLICAS variable and defines the number of pods you want to have for your deployment.
  • To start a job, click on the play icon next to the job’s name.
  • Once you get to 100%, you cannot scale down, and you’d have to roll back by redeploying the old version using the rollback button in the environment page.
  • With INCREMENTAL_ROLLOUT_MODE set to manual and with STAGING_ENABLED
  • not all buildpacks support Auto Test yet
  • When a project has been marked as private, GitLab’s Container Registry requires authentication when downloading containers.
  • Authentication credentials will be valid while the pipeline is running, allowing for a successful initial deployment.
  • After the pipeline completes, Kubernetes will no longer be able to access the Container Registry.
  • We strongly advise using GitLab Container Registry with Auto DevOps in order to simplify configuration and prevent any unforeseen issues.
張 旭

你到底知不知道什麼是 Kubernetes? | Hwchiu Learning Note - 0 views

www.hwchiu.com/kubernetes-concept.html

kubernetes storage networking programming system

shared by 張 旭 on 03 Feb 19 - No Cached
  • Storage(儲存) 實際上一直都不是一個簡單處理的問題，從軟體面來看實際上牽扯到非常多的層級，譬如 Linux Kernel, FileSystem, Block/File-Level, Cache, Snapshot, Object Storage 等各式各樣的議題可以討論。
  • DRBD
  • 異地備援，容錯機制，快照，重複資料刪除等超多相關的議題基本上從來沒有一個完美的解法能夠滿足所有使用情境。
  • ...20 more annotations...
  • 管理者可能會直接在 NFS Server 上進行 MDADM 來設定相關的 Block Device 並且基於上面提供 Export 供 NFS 使用，甚至底層套用不同的檔案系統 (EXT4/BTF4) 來獲取不同的功能與效能。
  • Kubernetes 就只是 NFS Client 的角色
  • CSI(Container Storage Interface)。CSI 本身作為 Kubernetes 與 Storage Solution 的中介層。
  • 基本上 Pod 裡面每個 Container 會使用 Volume 這個物件來代表容器內的掛載點，而在外部實際上會透過 PVC 以及 PV 的方式來描述這個 Volume 背後的儲存方案伺服器的資訊。
  • 整體會透過 CSI 的元件們與最外面實際上的儲存設備連接，所有儲存相關的功能是否有實現，有支援全部都要仰賴最後面的實際提供者， kubernetes 只透過 CSI 的標準去執行。
  • 在網路部分也有與之對應的 CNI(Container Network Interface). kubernetes 透過 CNI 這個介面來與後方的 網路解決方案 溝通
  • CNI 最基本的要求就是在在對應的階段為對應的容器提供網路能力
  • 目前最常見也是 IPv4 + TCP/UDP 的傳輸方式，因此才會看到大部分的 CNI 都在講這些。
  • 希望所有容器彼此之間可以透過 IPv4 來互相存取彼此，不論是同節點或是跨節點的容器們都要可以滿足這個需求。
  • 容器間到底怎麼傳輸的，需不需要封裝，透過什麼網卡，要不要透過 NAT 處理? 這一切都是 CNI 介面背後的實現
  • 外部網路存取容器服務 (Service/Ingress)
  • kubernetes 在 Service/Ingress 中間自行實現了一個模組，大抵上稱為 kube-proxy, 其底層可以使用 iptables, IPVS, user-space software 等不同的實現方法，這部分是跟 CNI 完全無關。
  • CNI 跟 Service/Ingress 是會衝突的，也有可能彼此沒有配合，這中間沒有絕對的穩定整合。
  • CNI 一般會處理的部份，包含了容器內的 網卡數量,網卡名稱,網卡IP, 以及容器與外部節點的連接能力等
  • CRI (Container Runtime Interface) 或是 Device Plugin
  • 對於 kubernetes 來說，其實本身並不在意到底底下的容器化技術實際上是怎麼實現的，你要用 Docker, rkt, CRI-O 都無所謂，甚至背後是一個偽裝成 Container 的 Virtaul Machine virtlet 都可以。
  • 去思考到底為什麼自己本身的服務需要容器化，容器化可以帶來什麼優點
  • 太多太多的人都認為只要寫一個 Dockerfile 將原先的應用程式們全部包裝起來放在一起就是一個很好的容器 來使用了。
  • 最後就會發現根本把 Container 當作 Virtual Machine 來使用，然後再補一句 Contaienr 根本不好用啊
  • 容器化 不是把直接 Virtual Machine 的使用習慣換個環境使用就叫做 容器化，而是要從概念上去暸解與使用
張 旭

bbatsov/rails-style-guide: A community-driven Ruby on Rails 4 style guide - 0 views

github.com/...rails-style-guide

rails programming code style

shared by 張 旭 on 07 May 17 - No Cached
  • custom initialization code in config/initializers. The code in initializers executes on application startup
  • Keep initialization code for each gem in a separate file with the same name as the gem
  • Mark additional assets for precompilation
  • ...90 more annotations...
  • config/environments/production.rb
  • Create an additional staging environment that closely resembles the production one
  • Keep any additional configuration in YAML files under the config/ directory
  • Rails::Application.config_for(:yaml_file)
  • Use nested routes to express better the relationship between ActiveRecord models
  • nest routes more than 1 level deep then use the shallow: true option
  • namespaced routes to group related actions
  • Don't use match to define any routes unless there is need to map multiple request types among [:get, :post, :patch, :put, :delete] to a single action using :via option.
  • Keep the controllers skinny
  • all the business logic should naturally reside in the model
  • Share no more than two instance variables between a controller and a view.
  • using a template
  • Prefer render plain: over render text
  • Prefer corresponding symbols to numeric HTTP status codes
  • without abbreviations
  • Keep your models for business logic and data-persistence only
  • Avoid altering ActiveRecord defaults (table names, primary key, etc)
  • Group macro-style methods (has_many, validates, etc) in the beginning of the class definition
  • Prefer has_many :through to has_and_belongs_to_many
  • self[:attribute]
  • self[:attribute] = value
  • validates
  • Keep custom validators under app/validators
  • Consider extracting custom validators to a shared gem
  • preferable to make a class method instead which serves the same purpose of the named scope
  • returns an ActiveRecord::Relation object
  • .update_attributes
  • Override the to_param method of the model
  • Use the friendly_id gem. It allows creation of human-readable URLs by using some descriptive attribute of the model instead of its id
  • find_each to iterate over a collection of AR objects
  • .find_each
  • .find_each
  • Looping through a collection of records from the database (using the all method, for example) is very inefficient since it will try to instantiate all the objects at once
  • always call before_destroy callbacks that perform validation with prepend: true
  • Define the dependent option to the has_many and has_one associations
  • always use the exception raising bang! method or handle the method return value.
  • When persisting AR objects
  • Avoid string interpolation in queries
  • param will be properly escaped
  • Consider using named placeholders instead of positional placeholders
  • use of find over where when you need to retrieve a single record by id
  • use of find_by over where and find_by_attribute
  • use of where.not over SQL
  • use heredocs with squish
  • Keep the schema.rb (or structure.sql) under version control.
  • Use rake db:schema:load instead of rake db:migrate to initialize an empty database
  • Enforce default values in the migrations themselves instead of in the application layer
  • change_column_default
  • imposing data integrity from the Rails app is impossible
  • use the change method instead of up and down methods.
  • constructive migrations
  • use models in migrations, make sure you define them so that you don't end up with broken migrations in the future
  • Don't use non-reversible migration commands in the change method.
  • In this case, block will be used by create_table in rollback
  • Never call the model layer directly from a view
  • Never make complex formatting in the views, export the formatting to a method in the view helper or the model.
  • When the labels of an ActiveRecord model need to be translated, use the activerecord scope
  • Separate the texts used in the views from translations of ActiveRecord attributes
  • Place the locale files for the models in a folder locales/models
  • the texts used in the views in folder locales/views
  • config/application.rb config.i18n.load_path += Dir[Rails.root.join('config', 'locales', '**', '*.{rb,yml}')]
  • I18n.t
  • I18n.l
  • Use "lazy" lookup for the texts used in views.
  • Use the dot-separated keys in the controllers and models
  • Reserve app/assets for custom stylesheets, javascripts, or images
  • Third party code such as jQuery or bootstrap should be placed in vendor/assets
  • Provide both HTML and plain-text view templates
  • config.action_mailer.raise_delivery_errors = true
  • Use a local SMTP server like Mailcatcher in the development environment
  • Provide default settings for the host name
  • The _url methods include the host name and the _path methods don't
  • _url
  • Format the from and to addresses properly
  • default from:
  • sending html emails all styles should be inline
  • Sending emails while generating page response should be avoided. It causes delays in loading of the page and request can timeout if multiple email are sent.
  • .start_with?
  • .end_with?
  • &.
  • Config your timezone accordingly in application.rb
  • config.active_record.default_timezone = :local
  • it can be only :utc or :local
  • Don't use Time.parse
  • Time.zone.parse
  • Don't use Time.now
  • Time.zone.now
  • Put gems used only for development or testing in the appropriate group in the Gemfile
  • Add all OS X specific gems to a darwin group in the Gemfile, and all Linux specific gems to a linux group
  • Do not remove the Gemfile.lock from version control.
張 旭

The Asset Pipeline - Ruby on Rails Guides - 0 views

guides.rubyonrails.org/asset_pipeline.html

rails image javascript font CSS file

shared by 張 旭 on 29 Dec 14 - No Cached
  • provides a framework to concatenate and minify or compress JavaScript and CSS assets
  • adds the ability to write these assets in other languages and pre-processors such as CoffeeScript, Sass and ERB
  • invalidate the cache by altering this fingerprint
  • ...80 more annotations...
  • Rails 4 automatically adds the sass-rails, coffee-rails and uglifier gems to your Gemfile
  • reduce the number of requests that a browser makes to render a web page
  • Starting with version 3.1, Rails defaults to concatenating all JavaScript files into one master .js file and all CSS files into one master .css file
  • In production, Rails inserts an MD5 fingerprint into each filename so that the file is cached by the web browser
  • The technique sprockets uses for fingerprinting is to insert a hash of the content into the name, usually at the end.
  • asset minification or compression
  • The sass-rails gem is automatically used for CSS compression if included in Gemfile and no config.assets.css_compressor option is set.
  • Supported languages include Sass for CSS, CoffeeScript for JavaScript, and ERB for both by default.
  • When a filename is unique and based on its content, HTTP headers can be set to encourage caches everywhere (whether at CDNs, at ISPs, in networking equipment, or in web browsers) to keep their own copy of the content
  • asset pipeline is technically no longer a core feature of Rails 4
  • Rails uses for fingerprinting is to insert a hash of the content into the name, usually at the end
  • With the asset pipeline, the preferred location for these assets is now the app/assets directory.
  • Fingerprinting is enabled by default for production and disabled for all other environments
  • The files in app/assets are never served directly in production.
  • Paths are traversed in the order that they occur in the search path
  • You should use app/assets for files that must undergo some pre-processing before they are served.
  • By default .coffee and .scss files will not be precompiled on their own
  • app/assets is for assets that are owned by the application, such as custom images, JavaScript files or stylesheets.
  • lib/assets is for your own libraries' code that doesn't really fit into the scope of the application or those libraries which are shared across applications.
  • vendor/assets is for assets that are owned by outside entities, such as code for JavaScript plugins and CSS frameworks.
  • Any path under assets/* will be searched
  • By default these files will be ready to use by your application immediately using the require_tree directive.
  • By default, this means the files in app/assets take precedence, and will mask corresponding paths in lib and vendor
  • Sprockets uses files named index (with the relevant extensions) for a special purpose
  • Rails.application.config.assets.paths
  • causes turbolinks to check if an asset has been updated and if so loads it into the page
  • if you add an erb extension to a CSS asset (for example, application.css.erb), then helpers like asset_path are available in your CSS rules
  • If you add an erb extension to a JavaScript asset, making it something such as application.js.erb, then you can use the asset_path helper in your JavaScript code
  • The asset pipeline automatically evaluates ERB
  • data URI — a method of embedding the image data directly into the CSS file — you can use the asset_data_uri helper.
  • Sprockets will also look through the paths specified in config.assets.paths, which includes the standard application paths and any paths added by Rails engines.
  • image_tag
  • the closing tag cannot be of the style -%>
  • asset_data_uri
  • app/assets/javascripts/application.js
  • sass-rails provides -url and -path helpers (hyphenated in Sass, underscored in Ruby) for the following asset classes: image, font, video, audio, JavaScript and stylesheet.
  • Rails.application.config.assets.compress
  • In JavaScript files, the directives begin with //=
  • The require_tree directive tells Sprockets to recursively include all JavaScript files in the specified directory into the output.
  • manifest files contain directives — instructions that tell Sprockets which files to require in order to build a single CSS or JavaScript file.
  • You should not rely on any particular order among those
  • Sprockets uses manifest files to determine which assets to include and serve.
  • the family of require directives prevents files from being included twice in the output
  • which files to require in order to build a single CSS or JavaScript file
  • Directives are processed top to bottom, but the order in which files are included by require_tree is unspecified.
  • In JavaScript files, Sprockets directives begin with //=
  • If require_self is called more than once, only the last call is respected.
  • require directive is used to tell Sprockets the files you wish to require.
  • You need not supply the extensions explicitly. Sprockets assumes you are requiring a .js file when done from within a .js file
  • paths must be specified relative to the manifest file
  • require_directory
  • Rails 4 creates both app/assets/javascripts/application.js and app/assets/stylesheets/application.css regardless of whether the --skip-sprockets option is used when creating a new rails application.
  • The file extensions used on an asset determine what preprocessing is applied.
  • app/assets/stylesheets/application.css
  • Additional layers of preprocessing can be requested by adding other extensions, where each extension is processed in a right-to-left manner
  • require_self
  • use the Sass @import rule instead of these Sprockets directives.
  • Keep in mind that the order of these preprocessors is important
  • In development mode, assets are served as separate files in the order they are specified in the manifest file.
  • when these files are requested they are processed by the processors provided by the coffee-script and sass gems and then sent back to the browser as JavaScript and CSS respectively.
  • css.scss.erb
  • js.coffee.erb
  • Keep in mind the order of these preprocessors is important.
  • By default Rails assumes that assets have been precompiled and will be served as static assets by your web server
  • with the Asset Pipeline the :cache and :concat options aren't used anymore
  • Assets are compiled and cached on the first request after the server is started
  • RAILS_ENV=production bundle exec rake assets:precompile
  • Debug mode can also be enabled in Rails helper methods
  • If you set config.assets.initialize_on_precompile to false, be sure to test rake assets:precompile locally before deploying
  • By default Rails assumes assets have been precompiled and will be served as static assets by your web server.
  • a rake task to compile the asset manifests and other files in the pipeline
  • RAILS_ENV=production bin/rake assets:precompile
  • a recipe to handle this in deployment
  • links the folder specified in config.assets.prefix to shared/assets
  • config/initializers/assets.rb
  • The initialize_on_precompile change tells the precompile task to run without invoking Rails
  • The X-Sendfile header is a directive to the web server to ignore the response from the application, and instead serve a specified file from disk
  • the jquery-rails gem which comes with Rails as the standard JavaScript library gem.
  • Possible options for JavaScript compression are :closure, :uglifier and :yui
  • concatenate assets
張 旭

Getting Started with Rails - Ruby on Rails Guides - 0 views

guides.rubyonrails.org/getting_started.html

shared by 張 旭 on 22 Jan 14 - Cached
  • A controller's purpose is to receive specific requests for the application.
  • Routing decides which controller receives which requests
  • The view should just display that information
  • ...55 more annotations...
  • view templates are written in a language called ERB (Embedded Ruby) which is converted by the request cycle in Rails before being sent to the user.
  • Each action's purpose is to collect information to provide it to a view.
  • A view's purpose is to display this information in a human readable format.
  • routing file which holds entries in a special DSL (domain-specific language) that tells Rails how to connect incoming requests to controllers and actions.
  • You can create, read, update and destroy items for a resource and these operations are referred to as CRUD operations
  • A controller is simply a class that is defined to inherit from ApplicationController.
  • If not found, then it will attempt to load a template called application/new. It looks for one here because the PostsController inherits from ApplicationController
  • :formats specifies the format of template to be served in response. The default format is :html, and so Rails is looking for an HTML template.
  • :handlers, is telling us what template handlers could be used to render our template.
  • When you call form_for, you pass it an identifying object for this form. In this case, it's the symbol :post. This tells the form_for helper what this form is for.
  • that the action attribute for the form is pointing at /posts/new
  • When a form is submitted, the fields of the form are sent to Rails as parameters.
  • parameters can then be referenced inside the controller actions, typically to perform a particular task
  • params method is the object which represents the parameters (or fields) coming in from the form.
  • Active Record is smart enough to automatically map column names to model attributes,
  • Rails uses rake commands to run migrations, and it's possible to undo a migration after it's been applied to your database
  • every Rails model can be initialized with its respective attributes, which are automatically mapped to the respective database columns.
  • migration creates a method named change which will be called when you run this migration.
  • The action defined in this method is also reversible, which means Rails knows how to reverse the change made by this migration, in case you want to reverse it later
  • Migration filenames include a timestamp to ensure that they're processed in the order that they were created.
  • @post.save returns a boolean indicating whether the model was saved or not.
  • prevents an attacker from setting the model's attributes by manipulating the hash passed to the model.
  • If you want to link to an action in the same controller, you don't need to specify the :controller option, as Rails will use the current controller by default.
  • inherits from ActiveRecord::Base
  • Active Record supplies a great deal of functionality to your Rails models for free, including basic database CRUD (Create, Read, Update, Destroy) operations, data validation, as well as sophisticated search support and the ability to relate multiple models to one another.
  • Rails includes methods to help you validate the data that you send to models
  • Rails can validate a variety of conditions in a model, including the presence or uniqueness of columns, their format, and the existence of associated objects.
  • redirect_to will tell the browser to issue another request.
  • rendering is done within the same request as the form submission
  • Each request for a comment has to keep track of the post to which the comment is attached, thus the initial call to the find method of the Post model to get the post in question.
  • pluralize is a rails helper that takes a number and a string as its arguments. If the number is greater than one, the string will be automatically pluralized.
  • The render method is used so that the @post object is passed back to the new template when it is rendered.
  • The method: :patch option tells Rails that we want this form to be submitted via the PATCH HTTP method which is the HTTP method you're expected to use to update resources according to the REST protocol.
  • it accepts a hash containing the attributes that you want to update.
  • field_with_errors. You can define a css rule to make them standout
  • belongs_to :post, which sets up an Active Record association
  • creates comments as a nested resource within posts
  • call destroy on Active Record objects when you want to delete them from the database.
  • Rails allows you to use the dependent option of an association to achieve this.
  • store all external data as UTF-8
  • you're better off ensuring that all external data is UTF-8
  • use UTF-8 as the internal storage of your database
  • Rails defaults to converting data from your database into UTF-8 at the boundary.
  • :patch
  • By default forms built with the form_for helper are sent via POST
  • The :method and :'data-confirm' options are used as HTML5 attributes so that when the link is clicked, Rails will first show a confirm dialog to the user, and then submit the link with method delete. This is done via the JavaScript file jquery_ujs which is automatically included into your application's layout (app/views/layouts/application.html.erb) when you generated the application.
  • Without this file, the confirmation dialog box wouldn't appear.
  • just defines the partial template we want to render
  • As the render method iterates over the @post.comments collection, it assigns each comment to
  • a local variable named the same as the partial
  • use the authentication system
  • require and permit
  • the method is often made private to make sure it can't be called outside its intended context.
  • standard CRUD actions in each controller in the following order: index, show, new, edit, create, update and destroy.
  • must be placed before any private or protected method in the controller in order to work
張 旭

ruby-grape/grape: An opinionated framework for creating REST-like APIs in Ruby. - 0 views

github.com/grape

api rails ruby

shared by 張 旭 on 17 Dec 16 - No Cached
  • Grape is a REST-like API framework for Ruby.
  • designed to run on Rack or complement existing web application frameworks such as Rails and Sinatra by providing a simple DSL to easily develop RESTful APIs
  • Grape APIs are Rack applications that are created by subclassing Grape::API
  • ...54 more annotations...
  • Rails expects a subdirectory that matches the name of the Ruby module and a file name that matches the name of the class
  • mount multiple API implementations inside another one
  • mount on a path, which is similar to using prefix inside the mounted API itself.
  • four strategies in which clients can reach your API's endpoints: :path, :header, :accept_version_header and :param
  • clients should pass the desired version as a request parameter, either in the URL query string or in the request body.
  • clients should pass the desired version in the HTTP Accept head
  • clients should pass the desired version in the UR
  • clients should pass the desired version in the HTTP Accept-Version header.
  • add a description to API methods and namespaces
  • Request parameters are available through the params hash object
  • Parameters are automatically populated from the request body on POST and PUT
  • route string parameters will have precedence.
  • Grape allows you to access only the parameters that have been declared by your params block
  • By default declared(params) includes parameters that have nil values
  • all valid types
  • type: File
  • JSON objects and arrays of objects are accepted equally
  • any class can be used as a type so long as an explicit coercion method is supplied
  • As a special case, variant-member-type collections may also be declared, by passing a Set or Array with more than one member to type
  • Parameters can be nested using group or by calling requires or optional with a block
  • relevant if another parameter is given
  • Parameters options can be grouped
  • allow_blank can be combined with both requires and optional
  • Parameters can be restricted to a specific set of values
  • Parameters can be restricted to match a specific regular expression
  • Never define mutually exclusive sets with any required params
  • Namespaces allow parameter definitions and apply to every method within the namespace
  • define a route parameter as a namespace using route_param
  • create custom validation that use request to validate the attribute
  • rescue a Grape::Exceptions::ValidationErrors and respond with a custom response or turn the response into well-formatted JSON for a JSON API that separates individual parameters and the corresponding error messages
  • custom validation messages
  • Request headers are available through the headers helper or from env in their original form
  • define requirements for your named route parameters using regular expressions on namespace or endpoint
  • route will match only if all requirements are met
  • mix in a module
  • define reusable params
  • using cookies method
  • a 201 for POST-Requests
  • 204 for DELETE-Requests
  • 200 status code for all other Requests
  • use status to query and set the actual HTTP Status Code
  • raising errors with error!
  • It is very crucial to define this endpoint at the very end of your API, as it literally accepts every request.
  • rescue_from will rescue the exceptions listed and all their subclasses.
  • Grape::API provides a logger method which by default will return an instance of the Logger class from Ruby's standard library.
  • Grape supports a range of ways to present your data
  • Grape has built-in Basic and Digest authentication (the given block is executed in the context of the current Endpoint).
  • Authentication applies to the current namespace and any children, but not parents.
  • Blocks can be executed before or after every API call, using before, after, before_validation and after_validation
  • Before and after callbacks execute in the following order
  • Grape by default anchors all request paths, which means that the request URL should match from start to end to match
  • The namespace method has a number of aliases, including: group, resource, resources, and segment. Use whichever reads the best for your API.
  • test a Grape API with RSpec by making HTTP requests and examining the response
  • POST JSON data and specify the correct content-type.
張 旭

Best practices for writing Dockerfiles | Docker Documentation - 0 views

docs.docker.com/...dockerfile_best-practices

docker system

shared by 張 旭 on 28 Sep 18 - No Cached
  • building efficient images
  • Docker builds images automatically by reading the instructions from a Dockerfile -- a text file that contains all commands, in order, needed to build a given image.
  • A Docker image consists of read-only layers each of which represents a Dockerfile instruction.
  • ...47 more annotations...
  • The layers are stacked and each one is a delta of the changes from the previous layer
  • When you run an image and generate a container, you add a new writable layer (the “container layer”) on top of the underlying layers.
  • By “ephemeral,” we mean that the container can be stopped and destroyed, then rebuilt and replaced with an absolute minimum set up and configuration.
  • Inadvertently including files that are not necessary for building an image results in a larger build context and larger image size.
  • To exclude files not relevant to the build (without restructuring your source repository) use a .dockerignore file. This file supports exclusion patterns similar to .gitignore files.
  • minimize image layers by leveraging build cache.
  • if your build contains several layers, you can order them from the less frequently changed (to ensure the build cache is reusable) to the more frequently changed
  • avoid installing extra or unnecessary packages just because they might be “nice to have.”
  • Each container should have only one concern.
  • Decoupling applications into multiple containers makes it easier to scale horizontally and reuse containers
  • Limiting each container to one process is a good rule of thumb, but it is not a hard and fast rule.
  • Use your best judgment to keep containers as clean and modular as possible.
  • do multi-stage builds and only copy the artifacts you need into the final image. This allows you to include tools and debug information in your intermediate build stages without increasing the size of the final image.
  • avoid duplication of packages and make the list much easier to update.
  • When building an image, Docker steps through the instructions in your Dockerfile, executing each in the order specified.
  • the next instruction is compared against all child images derived from that base image to see if one of them was built using the exact same instruction. If not, the cache is invalidated.
  • simply comparing the instruction in the Dockerfile with one of the child images is sufficient.
  • For the ADD and COPY instructions, the contents of the file(s) in the image are examined and a checksum is calculated for each file.
  • If anything has changed in the file(s), such as the contents and metadata, then the cache is invalidated.
  • cache checking does not look at the files in the container to determine a cache match.
  • In that case just the command string itself is used to find a match.
    • 張 旭
      張 旭 on 28 Sep 18
       
      RUN apt-get 這樣的指令，直接比對指令內容的意思。
  • Whenever possible, use current official repositories as the basis for your images.
  • Using RUN apt-get update && apt-get install -y ensures your Dockerfile installs the latest package versions with no further coding or manual intervention.
  • cache busting
  • Docker executes these commands using the /bin/sh -c interpreter, which only evaluates the exit code of the last operation in the pipe to determine success.
  • set -o pipefail && to ensure that an unexpected error prevents the build from inadvertently succeeding.
  • The CMD instruction should be used to run the software contained by your image, along with any arguments.
  • CMD should almost always be used in the form of CMD [“executable”, “param1”, “param2”…]
  • CMD should rarely be used in the manner of CMD [“param”, “param”] in conjunction with ENTRYPOINT
  • The ENV instruction is also useful for providing required environment variables specific to services you wish to containerize,
  • Each ENV line creates a new intermediate layer, just like RUN commands
  • COPY is preferred
  • COPY only supports the basic copying of local files into the container
  • the best use for ADD is local tar file auto-extraction into the image, as in ADD rootfs.tar.xz /
  • If you have multiple Dockerfile steps that use different files from your context, COPY them individually, rather than all at once.
  • using ADD to fetch packages from remote URLs is strongly discouraged; you should use curl or wget instead
  • The best use for ENTRYPOINT is to set the image’s main command, allowing that image to be run as though it was that command (and then use CMD as the default flags).
  • the image name can double as a reference to the binary as shown in the command
  • The VOLUME instruction should be used to expose any database storage area, configuration storage, or files/folders created by your docker container.
  • use VOLUME for any mutable and/or user-serviceable parts of your image
  • If you absolutely need functionality similar to sudo, such as initializing the daemon as root but running it as non-root), consider using “gosu”.
  • always use absolute paths for your WORKDIR
  • An ONBUILD command executes after the current Dockerfile build completes.
  • Think of the ONBUILD command as an instruction the parent Dockerfile gives to the child Dockerfile
  • A Docker build executes ONBUILD commands before any command in a child Dockerfile.
  • Be careful when putting ADD or COPY in ONBUILD. The “onbuild” image fails catastrophically if the new build’s context is missing the resource being added.
張 旭

Helm | - 0 views

helm.sh/using_helm

kubernetes helm system

shared by 張 旭 on 17 Jul 19 - No Cached
  • Helm will figure out where to install Tiller by reading your Kubernetes configuration file (usually $HOME/.kube/config). This is the same file that kubectl uses.
  • kubectl cluster-info
  • Role-Based Access Control (RBAC) enabled
  • ...133 more annotations...
  • initialize the local CLI
  • install Tiller into your Kubernetes cluster
  • helm install
  • helm init --upgrade
  • By default, when Tiller is installed, it does not have authentication enabled.
  • helm repo update
  • Without a max history set the history is kept indefinitely, leaving a large number of records for helm and tiller to maintain.
  • helm init --upgrade
  • Whenever you install a chart, a new release is created.
  • one chart can be installed multiple times into the same cluster. And each can be independently managed and upgraded.
  • helm list function will show you a list of all deployed releases.
  • helm delete
  • helm status
  • you can audit a cluster’s history, and even undelete a release (with helm rollback).
  • the Helm server (Tiller).
  • The Helm client (helm)
  • brew install kubernetes-helm
  • Tiller, the server portion of Helm, typically runs inside of your Kubernetes cluster.
  • it can also be run locally, and configured to talk to a remote Kubernetes cluster.
  • Role-Based Access Control - RBAC for short
  • create a service account for Tiller with the right roles and permissions to access resources.
  • run Tiller in an RBAC-enabled Kubernetes cluster.
  • run kubectl get pods --namespace kube-system and see Tiller running.
  • helm inspect
  • Helm will look for Tiller in the kube-system namespace unless --tiller-namespace or TILLER_NAMESPACE is set.
  • For development, it is sometimes easier to work on Tiller locally, and configure it to connect to a remote Kubernetes cluster.
  • even when running locally, Tiller will store release configuration in ConfigMaps inside of Kubernetes.
  • helm version should show you both the client and server version.
  • Tiller stores its data in Kubernetes ConfigMaps, you can safely delete and re-install Tiller without worrying about losing any data.
  • helm reset
  • The --node-selectors flag allows us to specify the node labels required for scheduling the Tiller pod.
  • --override allows you to specify properties of Tiller’s deployment manifest.
  • helm init --override manipulates the specified properties of the final manifest (there is no “values” file).
  • The --output flag allows us skip the installation of Tiller’s deployment manifest and simply output the deployment manifest to stdout in either JSON or YAML format.
  • By default, tiller stores release information in ConfigMaps in the namespace where it is running.
  • switch from the default backend to the secrets backend, you’ll have to do the migration for this on your own.
  • a beta SQL storage backend that stores release information in an SQL database (only postgres has been tested so far).
  • Once you have the Helm Client and Tiller successfully installed, you can move on to using Helm to manage charts.
  • Helm requires that kubelet have access to a copy of the socat program to proxy connections to the Tiller API.
  • A Release is an instance of a chart running in a Kubernetes cluster. One chart can often be installed many times into the same cluster.
  • helm init --client-only
  • helm init --dry-run --debug
  • A panic in Tiller is almost always the result of a failure to negotiate with the Kubernetes API server
  • Tiller and Helm have to negotiate a common version to make sure that they can safely communicate without breaking API assumptions
  • helm delete --purge
  • Helm stores some files in $HELM_HOME, which is located by default in ~/.helm
  • A Chart is a Helm package. It contains all of the resource definitions necessary to run an application, tool, or service inside of a Kubernetes cluster.
  • it like the Kubernetes equivalent of a Homebrew formula, an Apt dpkg, or a Yum RPM file.
  • A Repository is the place where charts can be collected and shared.
  • Set the $HELM_HOME environment variable
  • each time it is installed, a new release is created.
  • Helm installs charts into Kubernetes, creating a new release for each installation. And to find new charts, you can search Helm chart repositories.
  • chart repository is named stable by default
  • helm search shows you all of the available charts
  • helm inspect
  • To install a new package, use the helm install command. At its simplest, it takes only one argument: The name of the chart.
  • If you want to use your own release name, simply use the --name flag on helm install
  • additional configuration steps you can or should take.
  • Helm does not wait until all of the resources are running before it exits. Many charts require Docker images that are over 600M in size, and may take a long time to install into the cluster.
  • helm status
  • helm inspect values
  • helm inspect values stable/mariadb
  • override any of these settings in a YAML formatted file, and then pass that file during installation.
  • helm install -f config.yaml stable/mariadb
  • --values (or -f): Specify a YAML file with overrides.
  • --set (and its variants --set-string and --set-file): Specify overrides on the command line.
  • Values that have been --set can be cleared by running helm upgrade with --reset-values specified.
  • Chart designers are encouraged to consider the --set usage when designing the format of a values.yaml file.
  • --set-file key=filepath is another variant of --set. It reads the file and use its content as a value.
  • inject a multi-line text into values without dealing with indentation in YAML.
  • An unpacked chart directory
  • When a new version of a chart is released, or when you want to change the configuration of your release, you can use the helm upgrade command.
  • Kubernetes charts can be large and complex, Helm tries to perform the least invasive upgrade.
  • It will only update things that have changed since the last release
  • $ helm upgrade -f panda.yaml happy-panda stable/mariadb
  • deployment
  • If both are used, --set values are merged into --values with higher precedence.
  • The helm get command is a useful tool for looking at a release in the cluster.
  • helm rollback
  • A release version is an incremental revision. Every time an install, upgrade, or rollback happens, the revision number is incremented by 1.
  • helm history
  • a release name cannot be re-used.
  • you can rollback a deleted resource, and have it re-activate.
  • helm repo list
  • helm repo add
  • helm repo update
  • The Chart Development Guide explains how to develop your own charts.
  • helm create
  • helm lint
  • helm package
  • Charts that are archived can be loaded into chart repositories.
  • chart repository server
  • Tiller can be installed into any namespace.
  • Limiting Tiller to only be able to install into specific namespaces and/or resource types is controlled by Kubernetes RBAC roles and rolebindings
  • Release names are unique PER TILLER INSTANCE
  • Charts should only contain resources that exist in a single namespace.
  • not recommended to have multiple Tillers configured to manage resources in the same namespace.
  • a client-side Helm plugin. A plugin is a tool that can be accessed through the helm CLI, but which is not part of the built-in Helm codebase.
  • Helm plugins are add-on tools that integrate seamlessly with Helm. They provide a way to extend the core feature set of Helm, but without requiring every new feature to be written in Go and added to the core tool.
  • Helm plugins live in $(helm home)/plugins
  • The Helm plugin model is partially modeled on Git’s plugin model
  • helm referred to as the porcelain layer, with plugins being the plumbing.
  • helm plugin install https://github.com/technosophos/helm-template
  • command is the command that this plugin will execute when it is called.
  • Environment variables are interpolated before the plugin is executed.
  • The command itself is not executed in a shell. So you can’t oneline a shell script.
  • Helm is able to fetch Charts using HTTP/S
  • Variables like KUBECONFIG are set for the plugin if they are set in the outer environment.
  • In Kubernetes, granting a role to an application-specific service account is a best practice to ensure that your application is operating in the scope that you have specified.
  • restrict Tiller’s capabilities to install resources to certain namespaces, or to grant a Helm client running access to a Tiller instance.
  • Service account with cluster-admin role
  • The cluster-admin role is created by default in a Kubernetes cluster
  • Deploy Tiller in a namespace, restricted to deploying resources only in that namespace
  • Deploy Tiller in a namespace, restricted to deploying resources in another namespace
  • When running a Helm client in a pod, in order for the Helm client to talk to a Tiller instance, it will need certain privileges to be granted.
  • SSL Between Helm and Tiller
  • The Tiller authentication model uses client-side SSL certificates.
  • creating an internal CA, and using both the cryptographic and identity functions of SSL.
  • Helm is a powerful and flexible package-management and operations tool for Kubernetes.
  • default installation applies no security configurations
  • with a cluster that is well-secured in a private network with no data-sharing or no other users or teams.
  • With great power comes great responsibility.
  • Choose the Best Practices you should apply to your helm installation
  • Role-based access control, or RBAC
  • Tiller’s gRPC endpoint and its usage by Helm
  • Kubernetes employ a role-based access control (or RBAC) system (as do modern operating systems) to help mitigate the damage that can be done if credentials are misused or bugs exist.
  • In the default installation the gRPC endpoint that Tiller offers is available inside the cluster (not external to the cluster) without authentication configuration applied.
  • Tiller stores its release information in ConfigMaps. We suggest changing the default to Secrets.
  • release information
  • charts
  • charts are a kind of package that not only installs containers you may or may not have validated yourself, but it may also install into more than one namespace.
  • As with all shared software, in a controlled or shared environment you must validate all software you install yourself before you install it.
  • Helm’s provenance tools to ensure the provenance and integrity of charts
  • 張 旭 on 17 Jul 19
     
    "Helm will figure out where to install Tiller by reading your Kubernetes configuration file (usually $HOME/.kube/config). This is the same file that kubectl uses."
張 旭

Template Designer Documentation - Jinja2 Documentation (2.10) - 0 views

jinja.pocoo.org/...templates

python jinja template programming

shared by 張 旭 on 18 Feb 19 - No Cached
  • A Jinja template doesn’t need to have a specific extension
  • A Jinja template is simply a text file
  • tags, which control the logic of the template
  • ...106 more annotations...
  • {% ... %} for Statements
  • {{ ... }} for Expressions to print to the template output
  • use a dot (.) to access attributes of a variable
  • the outer double-curly braces are not part of the variable, but the print statement.
  • If you access variables inside tags don’t put the braces around them.
  • If a variable or attribute does not exist, you will get back an undefined value.
  • the default behavior is to evaluate to an empty string if printed or iterated over, and to fail for every other operation.
  • if an object has an item and attribute with the same name. Additionally, the attr() filter only looks up attributes.
  • Variables can be modified by filters. Filters are separated from the variable by a pipe symbol (|) and may have optional arguments in parentheses.
  • Multiple filters can be chained
  • Tests can be used to test a variable against a common expression.
  • add is plus the name of the test after the variable.
  • to find out if a variable is defined, you can do name is defined, which will then return true or false depending on whether name is defined in the current template context.
  • strip whitespace in templates by hand. If you add a minus sign (-) to the start or end of a block (e.g. a For tag), a comment, or a variable expression, the whitespaces before or after that block will be removed
  • not add whitespace between the tag and the minus sign
  • mark a block raw
  • Template inheritance allows you to build a base “skeleton” template that contains all the common elements of your site and defines blocks that child templates can override.
  • The {% extends %} tag is the key here. It tells the template engine that this template “extends” another template.
  • access templates in subdirectories with a slash
  • can’t define multiple {% block %} tags with the same name in the same template
  • use the special self variable and call the block with that name
  • self.title()
  • super()
  • put the name of the block after the end tag for better readability
  • if the block is replaced by a child template, a variable would appear that was not defined in the block or passed to the context.
  • setting the block to “scoped” by adding the scoped modifier to a block declaration
  • If you have a variable that may include any of the following chars (>, <, &, or ") you SHOULD escape it unless the variable contains well-formed and trusted HTML.
  • Jinja2 functions (macros, super, self.BLOCKNAME) always return template data that is marked as safe.
  • With the default syntax, control structures appear inside {% ... %} blocks.
  • the dictsort filter
  • loop.cycle
  • Unlike in Python, it’s not possible to break or continue in a loop
  • use loops recursively
  • add the recursive modifier to the loop definition and call the loop variable with the new iterable where you want to recurse.
  • The loop variable always refers to the closest (innermost) loop.
  • whether the value changed at all,
  • use it to test if a variable is defined, not empty and not false
  • Macros are comparable with functions in regular programming languages.
  • If a macro name starts with an underscore, it’s not exported and can’t be imported.
  • pass a macro to another macro
  • caller()
  • a single trailing newline is stripped if present
  • other whitespace (spaces, tabs, newlines etc.) is returned unchanged
  • a block tag works in “both” directions. That is, a block tag doesn’t just provide a placeholder to fill - it also defines the content that fills the placeholder in the parent.
  • Python dicts are not ordered
  • caller(user)
  • call(user)
  • This is a simple dialog rendered by using a macro and a call block.
  • Filter sections allow you to apply regular Jinja2 filters on a block of template data.
  • Assignments at top level (outside of blocks, macros or loops) are exported from the template like top level macros and can be imported by other templates.
  • using namespace objects which allow propagating of changes across scopes
  • use block assignments to capture the contents of a block into a variable name.
  • The extends tag can be used to extend one template from another.
  • Blocks are used for inheritance and act as both placeholders and replacements at the same time.
  • The include statement is useful to include a template and return the rendered contents of that file into the current namespace
  • Included templates have access to the variables of the active context by default.
  • putting often used code into macros
  • imports are cached and imported templates don’t have access to the current template variables, just the globals by default.
  • Macros and variables starting with one or more underscores are private and cannot be imported.
  • By default, included templates are passed the current context and imported templates are not.
  • imports are often used just as a module that holds macros.
  • Integers and floating point numbers are created by just writing the number down
  • Everything between two brackets is a list.
  • Tuples are like lists that cannot be modified (“immutable”).
  • A dict in Python is a structure that combines keys and values.
  • // Divide two numbers and return the truncated integer result
  • The special constants true, false, and none are indeed lowercase
  • all Jinja identifiers are lowercase
  • (expr) group an expression.
  • The is and in operators support negation using an infix notation
  • in Perform a sequence / mapping containment test.
  • | Applies a filter.
  • ~ Converts all operands into strings and concatenates them.
  • use inline if expressions.
  • always an attribute is returned and items are not looked up.
  • default(value, default_value=u'', boolean=False)¶ If the value is undefined it will return the passed default value, otherwise the value of the variable
  • dictsort(value, case_sensitive=False, by='key', reverse=False)¶ Sort a dict and yield (key, value) pairs.
  • format(value, *args, **kwargs)¶ Apply python string formatting on an object
  • groupby(value, attribute)¶ Group a sequence of objects by a common attribute.
  • grouping by is stored in the grouper attribute and the list contains all the objects that have this grouper in common.
  • indent(s, width=4, first=False, blank=False, indentfirst=None)¶ Return a copy of the string with each line indented by 4 spaces. The first line and blank lines are not indented by default.
  • join(value, d=u'', attribute=None)¶ Return a string which is the concatenation of the strings in the sequence.
  • map()¶ Applies a filter on a sequence of objects or looks up an attribute.
  • pprint(value, verbose=False)¶ Pretty print a variable. Useful for debugging.
  • reject()¶ Filters a sequence of objects by applying a test to each object, and rejecting the objects with the test succeeding.
  • replace(s, old, new, count=None)¶ Return a copy of the value with all occurrences of a substring replaced with a new one.
  • round(value, precision=0, method='common')¶ Round the number to a given precision
  • even if rounded to 0 precision, a float is returned.
  • select()¶ Filters a sequence of objects by applying a test to each object, and only selecting the objects with the test succeeding.
  • sort(value, reverse=False, case_sensitive=False, attribute=None)¶ Sort an iterable. Per default it sorts ascending, if you pass it true as first argument it will reverse the sorting.
  • striptags(value)¶ Strip SGML/XML tags and replace adjacent whitespace by one space.
  • tojson(value, indent=None)¶ Dumps a structure to JSON so that it’s safe to use in <script> tags.
  • trim(value)¶ Strip leading and trailing whitespace.
  • unique(value, case_sensitive=False, attribute=None)¶ Returns a list of unique items from the the given iterable
  • urlize(value, trim_url_limit=None, nofollow=False, target=None, rel=None)¶ Converts URLs in plain text into clickable links.
  • defined(value)¶ Return true if the variable is defined
  • in(value, seq)¶ Check if value is in seq.
  • mapping(value)¶ Return true if the object is a mapping (dict etc.).
  • number(value)¶ Return true if the variable is a number.
  • sameas(value, other)¶ Check if an object points to the same memory address than another object
  • undefined(value)¶ Like defined() but the other way round.
  • A joiner is passed a string and will return that string every time it’s called, except the first time (in which case it returns an empty string).
  • namespace(...)¶ Creates a new container that allows attribute assignment using the {% set %} tag
  • The with statement makes it possible to create a new inner scope. Variables set within this scope are not visible outside of the scope.
  • activate and deactivate the autoescaping from within the templates
  • With both trim_blocks and lstrip_blocks enabled, you can put block tags on their own lines, and the entire block line will be removed when rendered, preserving the whitespace of the contents
張 旭

Choose when to run jobs | GitLab - 0 views

docs.gitlab.com/...job_control.html

gitlab devops cicd

shared by 張 旭 on 28 Dec 21 - No Cached
  • Rules are evaluated in order until the first match.
  • no rules match, so the job is not added to any other pipeline.
  • define a set of rules to exclude jobs in a few cases, but run them in all other cases
  • ...32 more annotations...
  • use all rules keywords, like if, changes, and exists, in the same rule. The rule evaluates to true only when all included keywords evaluate to true.
  • use parentheses with && and || to build more complicated variable expressions.
  • Use workflow to specify which types of pipelines can run.
  • every push to an open merge request’s source branch causes duplicated pipelines.
  • avoid duplicate pipelines by changing the job rules to avoid either push (branch) pipelines or merge request pipelines.
  • do not mix only/except jobs with rules jobs in the same pipeline.
  • For behavior similar to the only/except keywords, you can check the value of the $CI_PIPELINE_SOURCE variable
  • commonly used variables for if clauses
  • rules:changes expressions to determine when to add jobs to a pipeline
  • Use !reference tags to reuse rules in different jobs.
  • Use except to define when a job does not run.
  • only or except used without refs is the same as only:refs / except/refs
  • If you change multiple files, but only one file ends in .md, the build job is still skipped.
  • If you use multiple keywords with only or except, the keywords are evaluated as a single conjoined expression.
  • only includes the job if all of the keys have at least one condition that matches.
  • except excludes the job if any of the keys have at least one condition that matches.
  • With only, individual keys are logically joined by an AND
  • With except, individual keys are logically joined by an OR
  • To specify a job as manual, add when: manual to the job in the .gitlab-ci.yml file.
  • Use protected environments to define a list of users authorized to run a manual job.
  • Use when: delayed to execute scripts after a waiting period, or if you want to avoid jobs immediately entering the pending state.
  • To split a large job into multiple smaller jobs that run in parallel, use the parallel keyword
  • run a trigger job multiple times in parallel in a single pipeline, but with different variable values for each instance of the job.
  • The @ symbol denotes the beginning of a ref’s repository path. To match a ref name that contains the @ character in a regular expression, you must use the hex character code match \x40.
  • Compare a variable to a string
  • Check if a variable is undefined
  • Check if a variable is empty
  • Check if a variable exists
  • Check if a variable is empty
  • Matches are found when using =~.
  • Matches are not found when using !~.
  • Join variable expressions together with && or ||
  • 張 旭 on 28 Dec 21
     
    "Rules are evaluated in order until the first match."
張 旭

我必须得告诉大家的MySQL优化原理 - 简书 - 0 views

www.jianshu.com/d7665192aaaf

mysql performance system

shared by 張 旭 on 19 Aug 17 - No Cached
  • 很多的查询优化工作实际上就是遵循一些原则让MySQL的优化器能够按照预想的合理方式运行而已
  • MySQL客户端/服务端通信协议是“半双工”的：在任一时刻，要么是服务器向客户端发送数据，要么是客户端向服务器发送数据，这两个动作不能同时发生。
  • 当查询语句很长的时候，需要设置max_allowed_packet参数。
  • ...70 more annotations...
  • 如果查询实在是太大，服务端会拒绝接收更多数据并抛出异常
  • 服务器响应给用户的数据通常会很多，由多个数据包组成
  • 减小通信间数据包的大小和数量是一个非常好的习惯
  • 查询中尽量避免使用SELECT *以及加上LIMIT限制
  • 在解析一个查询语句前，如果查询缓存是打开的，那么MySQL会检查这个查询语句是否命中查询缓存中的数据。
  • 两个查询在任何字符上的不同（例如：空格、注释），都会导致缓存不会命中。
  • MySQL将缓存存放在一个引用表
  • 如果查询中包含任何用户自定义函数、存储函数、用户变量、临时表、mysql库中的系统表，其查询结果 都不会被缓存。
  • MySQL的查询缓存系统会跟踪查询中涉及的每个表，如果这些表（数据或结构）发生变化，那么和这张表相关的所有缓存数据都将失效。
  • 在任何的写操作时，MySQL必须将对应表的所有缓存都设置为失效。
  • 查询缓存对系统的额外消耗也不仅仅在写操作，读操作也不例外
  • 任何的查询语句在开始之前都必须经过检查，即使这条SQL语句永远不会命中缓存
  • 如果查询结果可以被缓存，那么执行完成后，会将结果存入缓存，也会带来额外的系统消耗
  • 并不是什么情况下查询缓存都会提高系统性能，缓存和失效都会带来额外消耗
  • 用多个小表代替一个大表
  • 批量插入代替循环单条插入
  • 合理控制缓存空间大小
  • 可以通过SQL_CACHE和SQL_NO_CACHE来控制某个查询语句是否需要进行缓存
  • 不要轻易打开查询缓存，特别是写密集型应用
  • 将query_cache_type设置为DEMAND，这时只有加入SQL_CACHE的查询才会走缓存，其他查询则不会，这样可以非常自由地控制哪些查询需要被缓存。
  • 预处理则会根据MySQL规则进一步检查解析树是否合法。比如检查要查询的数据表和数据列是否存在等等。
  • 一条查询可以有很多种执行方式，最后都返回相应的结果。优化器的作用就是找到这其中最好的执行计划。
  • 查询当前会话的last_query_cost的值来得到其计算当前查询的成本。
  • 尝试预测一个查询使用某种执行计划时的成本
  • 有非常多的原因会导致MySQL选择错误的执行计划
  • MySQL值选择它认为成本小的，但成本小并不意味着执行时间短
  • 提前终止查询（比如：使用Limit时，查找到满足数量的结果集后会立即终止查询）
  • 找某列的最小值，如果该列有索引，只需要查找B+Tree索引最左端，反之则可以找到最大值
  • 在完成解析和优化阶段以后，MySQL会生成对应的执行计划，查询执行引擎根据执行计划给出的指令逐步执行得出结果。
  • 查询过程中的每一张表由一个handler实例表示。
  • MySQL在查询优化阶段就为每一张表创建了一个handler实例，优化器可以根据这些实例的接口来获取表的相关信息
  • 即使查询不到数据，MySQL仍然会返回这个查询的相关信息，比如改查询影响到的行数以及执行时间等等。
  • 结果集返回客户端是一个增量且逐步返回的过程
  • 整型就比字符操作代价低，因而会使用整型来存储ip地址，使用DATETIME来存储时间，而不是使用字符串。
  • 如果计划在列上创建索引，就应该将该列设置为NOT NULL
  • UNSIGNED表示不允许负值，大致可以使正数的上限提高一倍。
  • 没有太大的必要使用DECIMAL数据类型。即使是在需要存储财务数据时，仍然可以使用BIGINT
  • 大表ALTER TABLE非常耗时
  • MySQL执行大部分修改表结果操作的方法是用新的结构创建一个张空表，从旧表中查出所有的数据插入新表，然后再删除旧表
  • 索引是提高MySQL查询性能的一个重要途径，但过多的索引可能会导致过高的磁盘使用率以及过高的内存占用，从而影响应用程序的整体性能。
  • 索引是指B-Tree索引，它是目前关系型数据库中查找数据最为常用和有效的索引，大多数存储引擎都支持这种索引
  • B+Tree中的B是指balance，意为平衡。
  • 平衡二叉树首先需要符合二叉查找树的定义，其次必须满足任何节点的两个子树的高度差不能大于1。
  • 索引往往以索引文件的形式存储的磁盘上
  • 如何减少查找过程中的I/O存取次数？
  • 减少树的深度，将二叉树变为m叉树（多路搜索树），而B+Tree就是一种多路搜索树。
  • 页是计算机管理存储器的逻辑块，硬件及OS往往将主存和磁盘存储区分割为连续的大小相等的块
  • B+Tree为了保持平衡，对于新插入的值需要做大量的拆分页操作，而页的拆分需要I/O操作，为了尽可能的减少页的拆分操作，B+Tree也提供了类似于平衡二叉树的旋转功能。
  • 在多数情况下，在多个列上建立独立的索引并不能提高查询性能。理由非常简单，MySQL不知道选择哪个索引的查询效率更好
  • 当出现多个索引做联合操作时（多个OR条件），对结果集的合并、排序等操作需要耗费大量的CPU和内存资源，特别是当其中的某些索引的选择性不高，需要返回合并大量数据时，查询成本更高。
  • explain时如果发现有索引合并（Extra字段出现Using union），应该好好检查一下查询和表结构是不是已经是最优的
  • 索引选择性是指不重复的索引值和数据表的总记录数的比值
  • 唯一索引的选择性是1，这时最好的索引选择性，性能也是最好的。
  • 如果一个索引包含或者说覆盖所有需要查询的字段的值，那么就没有必要再回表查询，这就称为覆盖索引。
  • 对结果集进行排序的操作
  • 按照索引顺序扫描得出的结果自然是有序的
  • 如果explain的结果中type列的值为index表示使用了索引扫描来做排序。
  • 在设计索引时，如果一个索引既能够满足排序，有满足查询，是最好的。
  • 比如有一个索引(A,B)，再创建索引(A)就是冗余索引。
  • 对于非常小的表，简单的全表扫描更高效。对于中到大型的表，索引就非常有效。对于超大型的表，建立和维护索引的代价随之增长，这时候其他技术也许更有效，比如分区表。
  • explain后再提测是一种美德。
  • 如果要统计行数，直接使用COUNT(*)，意义清晰，且性能更好。
  • 执行EXPLAIN并不需要真正地去执行查询，所以成本非常低。
  • 确保ON和USING字句中的列上有索引。在创建索引的时候就要考虑到关联的顺序
  • 确保任何的GROUP BY和ORDER BY中的表达式只涉及到一个表中的列，这样MySQL才有可能使用索引来优化
  • MySQL关联执行的策略非常简单，它对任何的关联都执行嵌套循环关联操作，即先在一个表中循环取出单条数据，然后在嵌套循环到下一个表中寻找匹配的行，依次下去，直到找到所有表中匹配的行为为止。然后根据各个表匹配的行，返回查询中需要的各个列。
  • 最外层的查询是根据A.xx列来查询的，A.c上如果有索引的话，整个关联查询也不会使用。再看内层的查询，很明显B.c上如果有索引的话，能够加速查询，因此只需要在关联顺序中的第二张表的相应列上创建索引即可。
  • MySQL处理UNION的策略是先创建临时表，然后再把各个查询结果插入到临时表中，最后再来做查询。
  • 要使用UNION ALL，如果没有ALL关键字，MySQL会给临时表加上DISTINCT选项，这会导致整个临时表的数据做唯一性检查，这样做的代价非常高。
  • 尽可能不要使用存储过程
張 旭

plataformatec/simple_form - 0 views

github.com/...simple_form

rails gem form html

shared by 張 旭 on 29 Aug 16 - No Cached
  • The basic goal of Simple Form is to not touch your way of defining the layout
  • by default contains label, hints, errors and the input itself
  • Simple Form acts as a DSL and just maps your input type (retrieved from the column definition in the database) to a specific helper method.
  • ...68 more annotations...
  • can overwrite the default label by passing it to the input method
  • configure the html of any of them
  • disable labels, hints or error
  • add a hint, an error, or even a placeholder
  • add an inline label
  • pass any html attribute straight to the input, by using the :input_html option
  • use the :defaults option in simple_form_fo
  • Simple Form generates a wrapper div around your label and input by default, you can pass any html attribute to that wrapper as well using the :wrapper_html option,
  • By default all inputs are required
  • the required property of any input can be overwritten
  • Simple Form will look at the column type in the database and use an appropriate input for the column
  • lets you overwrite the default input type it creates
  • can also render boolean attributes using as: :select to show a dropdown.
  • give the :disabled option to Simple Form, and it'll automatically mark the wrapper as disabled with a CSS class
  • Simple Form accepts same options as their corresponding input type helper in Rails
  • Any extra option passed to these methods will be rendered as html option.
  • use label, hint, input_field, error and full_error helpers
  • to strip away all the div wrappers around the <input> field
  • is to use f.input_field
  • changing boolean_style from default value :nested to :inline
  • overriding the :collection option
  • Collections can be arrays or ranges, and when a :collection is given the :select input will be rendered by default
  • Other types of collection are :radio_buttons and :check_boxes
  • label_method
  • value_method
  • Both of these options also accept lambda/procs
  • define a to_label method on your model as Simple Form will search for and use :to_label as a :label_method first if it is found
  • create grouped collection selects, that will use the html optgroup tags
  • Grouped collection inputs accept the same :label_method and :value_method options
  • group_method
  • group_label_method
  • configured with a default value to be used on the site through the SimpleForm.country_priority and SimpleForm.time_zone_priority helpers.
  • association
  • association
  • render a :select input for choosing the :company, and another :select input with :multiple option for the :roles
  • all options available to :select, :radio_buttons and :check_boxes are also available to association
  • declare different labels and values
  • the association helper is currently only tested with Active Record
  • f.input
  • f.select
  • create a <button> element
  • simple_fields_for
  • Creates a collection of radio inputs with labels associated
  • Creates a collection of checkboxes with labels associated
  • collection_radio_buttons
  • collection_check_boxes
  • associations in your model
  • Role.all
  • the html element you will get for each attribute according to its database definition
  • redefine existing Simple Form inputs by creating a new class with the same name
  • Simple Form uses all power of I18n API to lookup labels, hints, prompts and placeholders
  • specify defaults for all models under the 'defaults' key
  • Simple Form will always look for a default attribute translation under the "defaults" key if no specific is found inside the model key
  • Simple Form will fallback to default human_attribute_name from Rails when no other translation is found for labels.
  • Simple Form will only do the lookup for options if you give a collection composed of symbols only.
  • "Add %{model}"
  • translations for labels, hints and placeholders for a namespaced model, e.g. Admin::User, should be placed under admin_user, not under admin/user
  • This difference exists because Simple Form relies on object_name provided by Rails' FormBuilder to determine the translation path for a given object instead of i18n_key from the object itself.
  • configure how your components will be rendered using the wrappers API
  • optional
  • unless_blank
  • By default, Simple Form will generate input field types and attributes that are supported in HTML5
  • The HTML5 extensions include the new field types such as email, number, search, url, tel, and the new attributes such as required, autofocus, maxlength, min, max, step.
  • If you want to have all other HTML 5 features, such as the new field types, you can disable only the browser validation
  • add novalidate to a specific form by setting the option on the form itself
  • the Simple Form configuration file
  • passing the html5 option
  • as: :date, html5: true
張 旭

Asset Pipeline - Ruby on Rails 指南 - 0 views

guides.ruby-china.org/asset_pipeline.html

shared by 張 旭 on 30 Jan 15 - No Cached
  • 清单文件或帮助方法
    • 張 旭
      張 旭 on 30 Jan 15
       
      清單文件是指：application.css 跟 application.js
  • Sprockets 会按照搜索路径中各路径出现的顺序进行搜索。默认情况下，这意味着 app/assets 文件夹中的静态资源优先级较高，会遮盖 lib 和 vendor 文件夹中的相应文件
  • 如果静态资源不会在清单文件中引入，就要添加到预编译的文件列表中，否则在生产环境中就无法访问文件。
  • ...36 more annotations...
  • 程序中使用了 jQuery 代码库和许多模块，都保存在 lib/assets/javascripts/library_name 文件夹中，那么 lib/assets/javascripts/library_name/index.js 文件的作用就是这个代码库的清单。清单文件中可以按顺序列出所需的文件，或者干脆使用 require_tree 指令。
  • 如果使用 Turbolinks（Rails 4 默认启用），加上 data-turbolinks-track 选项后，Turbolinks 会检查静态资源是否有更新，如果更新了就会将其载入页面
  • config.assets.paths 包含标准路径和其他 Rails 引擎添加的路径。
  • 链接不存在的资源（也包括链接到空字符串的情况）会在调用页面抛出异常。
  • 关闭标签不能使用 -%> 形式
  • Sprockets 通过清单文件决定要引入和伺服哪些静态资源
  • 在 JavaScript 文件中，Sprockets 的指令以 //= 开头。在上面的文件中，用到了 require 和 the require_tree 指令。
  • app/assets/javascripts/application.js
  • require_tree 指令告知 Sprockets 递归引入指定文件夹中的所有 JavaScript 文件。文件夹的路径必须相对于清单文件。也可使用 require_directory 指令加载指定文件夹中的所有 JavaScript 文件，但不会递归。
  • Sprockets 会按照从上至下的顺序处理指令，但 require_tree 引入的文件顺序是不可预期的，不要设想能得到一个期望的顺序。
  • app/assets/stylesheets/application.css
  • 不管创建新程序时有没有指定 --skip-sprockets 选项，Rails 4 都会生成 app/assets/javascripts/application.js 和 app/assets/stylesheets/application.css
  • 如果多次调用 require_self，只有最后一次调用有效
  • 如果想使用多个 Sass 文件，应该使用 Sass 中的 @import 规则，不要使用 Sprockets 指令。
  • 清单文件可以有多个。
  • 如果使用默认的 gem，生成控制器或脚手架时，会生成 CoffeeScript 和 SCSS 文件，而不是普通的 JavaScript 和 CSS 文件。
  • 在开发环境中，或者禁用 Asset Pipeline 时，这些文件会使用 coffee-script 和 sass 提供的预处理器处理，然后再发给浏览器
  • 启用 Asset Pipeline 时，这些文件会先使用预处理器处理，然后保存到 public/assets 文件夹中，再由 Rails 程序或网页服务器伺服
  • 添加额外的扩展名可以增加预处理次数，预处理程序会按照扩展名从右至左的顺序处理文件内容。所以，扩展名的顺序要和处理的顺序一致
  • 预处理器的执行顺序很重要
  • 在开发环境中也可启用压缩功能，检查是否能正常运行。需要调试时再禁用压缩即可。
  • 默认情况下，Rails 认为静态资源已经事先编译好了，直接由网页服务器伺服。
  • 般情况下，请勿修改 config.assets.digest 的默认值
  • 可在部署时编译静态资源
  • 在多次部署之间共用这个文件夹是十分重要的，这样只要缓存的页面可用，其中引用的编译后的静态资源就能正常使用。
  • 默认编译的文件包括 application.js、application.css 以及 gem 中 app/assets 文件夹中的所有非 JS/CSS 文件（会自动加载所有图片）
  • 如果想编译其他清单，或者单独的样式表和 JavaScript，可以添加到 config/application.rb 文件中的 precompile 选项
  • 设置编译所有静态资源
  • manifest-md5hash.json 的文件，列出所有静态资源和对应的指纹
  • 把 Expires 报头设置为很久以后
  • 在本地预编译后，可以把编译好的文件纳入版本控制系统，再按照常规的方式部署
  • 实时编译消耗的内存更多，比默认的编译方式性能更低，因此不推荐使用
  • 如果用 CDN 分发静态资源，要确保文件不会被缓存，因为缓存会导致问题。如果设置了 config.action_controller.perform_caching = true，Rack::Cache 会使用 Rails.cache 存储静态文件，很快缓存空间就会用完。
  • Sprockets 默认使用的公开路径是 /assets
  • X-Sendfile 报头的作用是让服务器忽略程序的响应，直接从硬盘上伺服指定的文件
  • 为 Rails 提供标准 JavaScript 代码库的 jquery-rails gem 是个很好的例子。这个 gem 中有个引擎类，继承自 Rails::Engine。添加这层继承关系后，Rails 就知道这个 gem 中可能包含静态资源文件，会把这个引擎中的 app/assets、lib/assets 和 vendor/assets 三个文件夹加入 Sprockets 的搜索路径中。
1 - 20 of 335 Next › Last »
Showing 20▼ items per page