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張 旭

Modules - Configuration Language - Terraform by HashiCorp - 0 views

www.terraform.io/...modules.html

terraform devops programming module

shared by 張 旭 on 07 Sep 19 - No Cached
  • provider blocks can appear in any module, it is recommended that they be placed only in the root module of a configuration
  • In all cases it is recommended to keep explicit provider configurations only in the root module and pass them (whether implicitly or explicitly) down to descendent modules
  • Provider configurations are used for all operations on associated resources, including destroying remote objects and refreshing state.
  • ...5 more annotations...
  • all resources created for a particular provider configuration must be destroyed before that provider configuration is removed, unless the related resources are re-configured to use a different provider configuration first.
  • a child module automatically inherits default (un-aliased) provider configurations from its parent.
  • recommended in the common case where only a single configuration is needed for each provider across the entire configuration.
  • the providers argument within a module block can be used to define explicitly which provider configs are made available to the child module.
  • Once the providers argument is used in a module block, it overrides all of the default inheritance behavior, so it is necessary to enumerate mappings for all of the required providers.
張 旭

Data Sources - Configuration Language - Terraform by HashiCorp - 0 views

www.terraform.io/...data-sources.html

terraform devops variable

shared by 張 旭 on 07 Apr 19 - No Cached
  • refer to this resource from elsewhere in the same Terraform module, but has no significance outside of the scope of a module.
  • A data block requests that Terraform read from a given data source ("aws_ami") and export the result under the given local name ("example").
  • A data source is accessed via a special kind of resource known as a data resource
  • 張 旭 on 07 Apr 19
     
    "refer to this resource from elsewhere in the same Terraform module, but has no significance outside of the scope of a module."
張 旭

How to create reusable infrastructure with Terraform modules - 0 views

blog.gruntwork.io/terraform-modules-25526d65f73d

terraform devops programming module

shared by 張 旭 on 05 Sep 19 - No Cached
  • auto scaling schedule
  • The easiest way to create a versioned module is to put the code for the module in a separate Git repository and to set the source parameter to that repository’s URL.
張 旭

Quick start - 0 views

terragrunt.gruntwork.io/...quick-start

devops terraform

shared by 張 旭 on 15 Jun 21 - No Cached
  • Terragrunt will forward almost all commands, arguments, and options directly to Terraform, but based on the settings in your terragrunt.hcl file
  • the backend configuration does not support variables or expressions of any sort
  • the path_relative_to_include() built-in function,
  • ...9 more annotations...
  • The generate attribute is used to inform Terragrunt to generate the Terraform code for configuring the backend.
  • The find_in_parent_folders() helper will automatically search up the directory tree to find the root terragrunt.hcl and inherit the remote_state configuration from it.
  • Unlike the backend configurations, provider configurations support variables,
  • if you needed to modify the configuration to expose another parameter (e.g session_name), you would have to then go through each of your modules to make this change.
  • instructs Terragrunt to create the file provider.tf in the working directory (where Terragrunt calls terraform) before it calls any of the Terraform commands
  • large modules should be considered harmful.
  • it is a Bad Idea to define all of your environments (dev, stage, prod, etc), or even a large amount of infrastructure (servers, databases, load balancers, DNS, etc), in a single Terraform module.
  • Large modules are slow, insecure, hard to update, hard to code review, hard to test, and brittle (i.e., you have all your eggs in one basket).
  • Terragrunt allows you to define your Terraform code once and to promote a versioned, immutable “artifact” of that exact same code from environment to environment.
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

1. Introduction · swooletw/laravel-swoole Wiki - 0 views

github.com/...1.-Introduction

php swoole performance

shared by 張 旭 on 24 Apr 19 - No Cached
  • when you run PHP script every time, PHP needs to initialize modules and launch Zend Engine for your running environment. And your PHP script needs to be compiled to OpCodes and then Zend Engine can finally execute them.
  • in traditional PHP lifecycle, it wastes a bunch of time building and destroying resources for your script execution.
  • have a built-in server on top of Swoole, and all the scripts can be kept in memory after the first load
  • 張 旭 on 24 Apr 19
     
    "when you run PHP script every time, PHP needs to initialize modules and launch Zend Engine for your running environment. And your PHP script needs to be compiled to OpCodes and then Zend Engine can finally execute them."
張 旭

State: Workspaces - Terraform by HashiCorp - 0 views

www.terraform.io/...workspaces.html

system devops terraform

shared by 張 旭 on 07 Apr 19 - No Cached
  • The persistent data stored in the backend belongs to a workspace.
  • Certain backends support multiple named workspaces, allowing multiple states to be associated with a single configuration.
  • Terraform starts with a single workspace named "default". This workspace is special both because it is the default and also because it cannot ever be deleted.
  • ...12 more annotations...
  • Within your Terraform configuration, you may include the name of the current workspace using the ${terraform.workspace} interpolation sequence.
  • changing behavior based on the workspace.
  • Named workspaces allow conveniently switching between multiple instances of a single configuration within its single backend.
  • A common use for multiple workspaces is to create a parallel, distinct copy of a set of infrastructure in order to test a set of changes before modifying the main production infrastructure.
  • Non-default workspaces are often related to feature branches in version control.
  • Workspaces alone are not a suitable tool for system decomposition, because each subsystem should have its own separate configuration and backend, and will thus have its own distinct set of workspaces.
  • In particular, organizations commonly want to create a strong separation between multiple deployments of the same infrastructure serving different development stages (e.g. staging vs. production) or different internal teams.
  • use one or more re-usable modules to represent the common elements, and then represent each instance as a separate configuration that instantiates those common elements in the context of a different backend.
  • If a Terraform state for one configuration is stored in a remote backend that is accessible to other configurations then terraform_remote_state can be used to directly consume its root module outputs from those other configurations.
  • For server addresses, use a provider-specific resource to create a DNS record with a predictable name and then either use that name directly or use the dns provider to retrieve the published addresses in other configurations.
  • Workspaces are technically equivalent to renaming your state file.
  • using a remote backend instead is recommended when there are multiple collaborators.
  • 張 旭 on 07 Apr 19
     
    "The persistent data stored in the backend belongs to a workspace."
crazylion lee

GitHub - stevekane/promise-it-wont-hurt: A Workshopper module that teaches you to use p... - 0 views

github.com/...promise-it-wont-hurt

javascript promise

shared by crazylion lee on 12 May 17 - No Cached
  • crazylion lee on 12 May 17
     
    "A Workshopper module that teaches you to use promises in javascript"
張 旭

Logstash Alternatives: Pros & Cons of 5 Log Shippers [2019] - Sematext - 0 views

sematext.com/...logstash-alternatives

log monitor system logstash fluentd

shared by 張 旭 on 05 Nov 19 - No Cached
  • In this case, Elasticsearch. And because Elasticsearch can be down or struggling, or the network can be down, the shipper would ideally be able to buffer and retry
  • Logstash is typically used for collecting, parsing, and storing logs for future use as part of log management.
  • Logstash’s biggest con or “Achille’s heel” has always been performance and resource consumption (the default heap size is 1GB).
  • ...37 more annotations...
  • This can be a problem for high traffic deployments, when Logstash servers would need to be comparable with the Elasticsearch ones.
  • Filebeat was made to be that lightweight log shipper that pushes to Logstash or Elasticsearch.
  • differences between Logstash and Filebeat are that Logstash has more functionality, while Filebeat takes less resources.
  • Filebeat is just a tiny binary with no dependencies.
  • For example, how aggressive it should be in searching for new files to tail and when to close file handles when a file didn’t get changes for a while.
  • For example, the apache module will point Filebeat to default access.log and error.log paths
  • Filebeat’s scope is very limited,
  • Initially it could only send logs to Logstash and Elasticsearch, but now it can send to Kafka and Redis, and in 5.x it also gains filtering capabilities.
  • Filebeat can parse JSON
  • you can push directly from Filebeat to Elasticsearch, and have Elasticsearch do both parsing and storing.
  • You shouldn’t need a buffer when tailing files because, just as Logstash, Filebeat remembers where it left off
  • For larger deployments, you’d typically use Kafka as a queue instead, because Filebeat can talk to Kafka as well
  • The default syslog daemon on most Linux distros, rsyslog can do so much more than just picking logs from the syslog socket and writing to /var/log/messages.
  • It can tail files, parse them, buffer (on disk and in memory) and ship to a number of destinations, including Elasticsearch.
  • rsyslog is the fastest shipper
  • Its grammar-based parsing module (mmnormalize) works at constant speed no matter the number of rules (we tested this claim).
  • use it as a simple router/shipper, any decent machine will be limited by network bandwidth
  • It’s also one of the lightest parsers you can find, depending on the configured memory buffers.
  • rsyslog requires more work to get the configuration right
  • the main difference between Logstash and rsyslog is that Logstash is easier to use while rsyslog lighter.
  • rsyslog fits well in scenarios where you either need something very light yet capable (an appliance, a small VM, collecting syslog from within a Docker container).
  • rsyslog also works well when you need that ultimate performance.
  • syslog-ng as an alternative to rsyslog (though historically it was actually the other way around).
  • a modular syslog daemon, that can do much more than just syslog
  • Unlike rsyslog, it features a clear, consistent configuration format and has nice documentation.
  • Similarly to rsyslog, you’d probably want to deploy syslog-ng on boxes where resources are tight, yet you do want to perform potentially complex processing.
  • syslog-ng has an easier, more polished feel than rsyslog, but likely not that ultimate performance
  • Fluentd was built on the idea of logging in JSON wherever possible (which is a practice we totally agree with) so that log shippers down the line don’t have to guess which substring is which field of which type.
  • Fluentd plugins are in Ruby and very easy to write.
  • structured data through Fluentd, it’s not made to have the flexibility of other shippers on this list (Filebeat excluded).
  • Fluent Bit, which is to Fluentd similar to how Filebeat is for Logstash.
  • Fluentd is a good fit when you have diverse or exotic sources and destinations for your logs, because of the number of plugins.
  • Splunk isn’t a log shipper, it’s a commercial logging solution
  • Graylog is another complete logging solution, an open-source alternative to Splunk.
  • everything goes through graylog-server, from authentication to queries.
  • Graylog is nice because you have a complete logging solution, but it’s going to be harder to customize than an ELK stack.
  • it depends
張 旭

Syntax - Configuration Language | Terraform | HashiCorp Developer - 0 views

developer.hashicorp.com/...configuration

devops terraform

shared by 張 旭 on 22 Jan 23 - No Cached
  • the native syntax of the Terraform language, which is a rich language designed to be relatively easy for humans to read and write.
  • Terraform's configuration language is based on a more general language called HCL, and HCL's documentation usually uses the word "attribute" instead of "argument."
  • A particular block type may have any number of required labels, or it may require none
  • ...34 more annotations...
  • After the block type keyword and any labels, the block body is delimited by the { and } characters
  • Identifiers can contain letters, digits, underscores (_), and hyphens (-). The first character of an identifier must not be a digit, to avoid ambiguity with literal numbers.
  • The # single-line comment style is the default comment style and should be used in most cases.
  • he idiomatic style is to use the Unix convention
  • Indent two spaces for each nesting level.
  • align their equals signs
  • Use empty lines to separate logical groups of arguments within a block.
  • Use one blank line to separate the arguments from the blocks.
  • "meta-arguments" (as defined by the Terraform language semantics)
  • Avoid separating multiple blocks of the same type with other blocks of a different type, unless the block types are defined by semantics to form a family.
  • Resource names must start with a letter or underscore, and may contain only letters, digits, underscores, and dashes.
  • Each resource is associated with a single resource type, which determines the kind of infrastructure object it manages and what arguments and other attributes the resource supports.
  • Each resource type is implemented by a provider, which is a plugin for Terraform that offers a collection of resource types.
  • By convention, resource type names start with their provider's preferred local name.
  • Most publicly available providers are distributed on the Terraform Registry, which also hosts their documentation.
  • The Terraform language defines several meta-arguments, which can be used with any resource type to change the behavior of resources.
  • use precondition and postcondition blocks to specify assumptions and guarantees about how the resource operates.
  • Some resource types provide a special timeouts nested block argument that allows you to customize how long certain operations are allowed to take before being considered to have failed.
  • Timeouts are handled entirely by the resource type implementation in the provider
  • Most resource types do not support the timeouts block at all.
  • A resource block declares that you want a particular infrastructure object to exist with the given settings.
  • Destroy resources that exist in the state but no longer exist in the configuration.
  • Destroy and re-create resources whose arguments have changed but which cannot be updated in-place due to remote API limitations.
  • Expressions within a Terraform module can access information about resources in the same module, and you can use that information to help configure other resources. Use the <RESOURCE TYPE>.<NAME>.<ATTRIBUTE> syntax to reference a resource attribute in an expression.
  • resources often provide read-only attributes with information obtained from the remote API; this often includes things that can't be known until the resource is created, like the resource's unique random ID.
  • data sources, which are a special type of resource used only for looking up information.
  • some dependencies cannot be recognized implicitly in configuration.
  • local-only resource types exist for generating private keys, issuing self-signed TLS certificates, and even generating random ids.
  • The behavior of local-only resources is the same as all other resources, but their result data exists only within the Terraform state.
  • The count meta-argument accepts a whole number, and creates that many instances of the resource or module.
  • count.index — The distinct index number (starting with 0) corresponding to this instance.
  • the count value must be known before Terraform performs any remote resource actions. This means count can't refer to any resource attributes that aren't known until after a configuration is applied
  • Within nested provisioner or connection blocks, the special self object refers to the current resource instance, not the resource block as a whole.
  • This was fragile, because the resource instances were still identified by their index instead of the string values in the list.
  • 張 旭 on 22 Jan 23
     
    "the native syntax of the Terraform language, which is a rich language designed to be relatively easy for humans to read and write. "
張 旭

Dependency Lock File (.terraform.lock.hcl) - Configuration Language | Terraform | Hashi... - 0 views

developer.hashicorp.com/...dependency-lock

devops terraform

shared by 張 旭 on 21 Jan 23 - No Cached
  • Version constraints within the configuration itself determine which versions of dependencies are potentially compatible, but after selecting a specific version of each dependency Terraform remembers the decisions it made in a dependency lock file
  • At present, the dependency lock file tracks only provider dependencies.
  • Terraform does not remember version selections for remote modules, and so Terraform will always select the newest available module version that meets the specified version constraints.
  • ...14 more annotations...
  • The lock file is always named .terraform.lock.hcl, and this name is intended to signify that it is a lock file for various items that Terraform caches in the .terraform
  • Terraform automatically creates or updates the dependency lock file each time you run the terraform init command.
  • You should include this file in your version control repository
  • If a particular provider has no existing recorded selection, Terraform will select the newest available version that matches the given version constraint, and then update the lock file to include that selection.
  • the "trust on first use" model
  • you can pre-populate checksums for a variety of different platforms in your lock file using the terraform providers lock command, which will then allow future calls to terraform init to verify that the packages available in your chosen mirror match the official packages from the provider's origin registry.
  • The h1: and zh: prefixes on these values represent different hashing schemes, each of which represents calculating a checksum using a different algorithm.
  • zh:: a mnemonic for "zip hash"
  • h1:: a mnemonic for "hash scheme 1", which is the current preferred hashing scheme.
  • To determine whether there still exists a dependency on a given provider, Terraform uses two sources of truth: the configuration itself, and the state.
  • Version constraints within the configuration itself determine which versions of dependencies are potentially compatible, but after selecting a specific version of each dependency Terraform remembers the decisions it made in a dependency lock file so that it can (by default) make the same decisions again in future.
  • At present, the dependency lock file tracks only provider dependencies.
  • Terraform will always select the newest available module version that meets the specified version constraints.
  • The lock file is always named .terraform.lock.hcl
  • 張 旭 on 21 Jan 23
     
    "the overriding effect is compounded, with later blocks taking precedence over earlier blocks."
crazylion lee

How to Learn Advanced Mathematics Without Heading to University - Part 3 - QuantStart - 0 views

www.quantstart.com/...t-Heading-to-University-Part-3

mathematics math

shared by crazylion lee on 27 Nov 16 - No Cached
  • crazylion lee on 27 Nov 16
     
    "In the first and second articles in the series we looked at the courses that are taken in the first half of a four-year undergraduate mathematics degree - and how to learn these modules on your own."
crazylion lee

I don't understand Python's Asyncio | Armin Ronacher's Thoughts and Writings - 0 views

lucumr.pocoo.org/...i-dont-understand-asyncio

python io async

shared by crazylion lee on 27 Nov 16 - No Cached
  • crazylion lee on 27 Nov 16
     
    "Recently I started looking into Python's new asyncio module a bit more. The reason for this is that I needed to do something that works better with evented IO and I figured I might give the new hot thing in the Python world a try. Primarily what I learned from this exercise is that I it's a much more complex system than I expected and I am now at the point where I am very confident that I do not know how to use it properly. It's not conceptionally hard to understand and borrows a lot from Twisted, but it has so many elements that play into it that I'm not sure any more how the individual bits and pieces are supposed to go together. Since I'm not clever enough to actually propose anything better I just figured I share my thoughts about what confuses me instead so that others might be able to use that in some capacity to understand it."
crazylion lee

Keepalived for Linux - 0 views

www.keepalived.org

clustering HA failover keepalived

shared by crazylion lee on 15 Aug 14 - Cached
  • crazylion lee on 15 Aug 14
     
    Keepalived is a routing software written in C. The main goal of this project is to provide simple and robust facilities for loadbalancing and high-availability to Linux system and Linux based infrastructures. Loadbalancing framework relies on well-known and widely used Linux Virtual Server (IPVS) kernel module providing Layer4 loadbalancing. Keepalived implements a set of checkers to dynamically and adaptively maintain and manage loadbalanced server pool according their health. On the other hand high-availability is achieved by VRRP protocol. VRRP is a fundamental brick for router failover. In addition, Keepalived implements a set of hooks to the VRRP finite state machine providing low-level and high-speed protocol interactions. Keepalived frameworks can be used independently or all together to provide resilient infrastructures.
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

3. Hello, world! - Err 9.9.9 documentation - 0 views

errbot.readthedocs.io/...basics.html

chatops

shared by 張 旭 on 18 Feb 22 - No Cached
  • The first is a Message object, which represents the full message object received by Errbot.
  • The second is a string (or a list, if using the split_args_with parameter of botcmd()) with the arguments passed to the command.
  • args would be the string “Mister Errbot”.
  • ...6 more annotations...
  • If you return None, Errbot will not respond with any kind of message when executing the command.
  • a file that ends with the extension .plug and it is used by Errbot to identify and load plugins.
  • The key Module should point to a module that Python can find and import.
  • The key Name should be identical to the name you gave to the class in your plugin file
  • The presence of __init__.py indicates lib is a Python regular package.
  • the !status command,
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

Containers Vs. Config Management - 0 views

blog.containership.io/config-management-e64cbb744a94

docker devops deploy config ansible puppet system

shared by 張 旭 on 16 Feb 17 - No Cached
  • With configuration management systems, you write code that describes how you want some component of your systems to be installed and configured, and when you execute the code on your server, it should end up in the desired state.
  • building a hosting platform that is capable of a lot of things that system administrators used to do manually
  • build modules on deployment via bundler or npm or similar, it can be incredibly slow to run, taking minutes or longer in some cases
  • ...10 more annotations...
  • pulling from git is slow.
  • deploying with configuration management tools is a pain in the ass and error prone.
  • Support for containers has existed in the Linux kernel since version 2.6.24 when cgroup support was added
  • All of the logic that used to live in your cookbooks/playbooks/manifests/etc now lives in a Dockerfile that resides directly in the repository for the application it is designed to build
  • All of the dependencies of the application are bundled with the container which means no need to build on the fly on every server during deployment.
  • Containers bring standardization which allows for systems like centralized logging, monitoring, and metrics to easily snap into place no matter what is running in the container.
  • Dockerfiles do not give you the same level of control over configuration as your application transitions between environments, like dev, staging, and production.
  • You may even need to have different Dockerfile’s for each environment in certain cases.
  • configuration management systems now have hooks for docker integration.
  • Config management will only be used to install Docker, an orchestration system, configure PAM/SSH auth, and tune OS sysctl values.
  • 張 旭 on 16 Feb 17
     
    "With configuration management systems, you write code that describes how you want some component of your systems to be installed and configured, and when you execute the code on your server, it should end up in the desired state."
張 旭

Using Infrastructure as Code to Automate VMware Deployments - 1 views

www.hashicorp.com/...to-automate-vmware-deployments

vmware devops system terraform

shared by 張 旭 on 28 Mar 19 - No Cached
  • Infrastructure as code is at the heart of provisioning for cloud infrastructure marking a significant shift away from monolithic point-and-click management tools.
  • infrastructure as code enables operators to take a programmatic approach to provisioning.
  • provides a single workflow to provision and maintain infrastructure and services from all of your vendors, making it not only easier to switch providers
  • ...5 more annotations...
  • A Terraform Provider is responsible for understanding API interactions between and exposing the resources from a given Infrastructure, Platform, or SaaS offering to Terraform.
  • write a Terraform file that describes the Virtual Machine that you want, apply that file with Terraform and create that VM as you described without ever needing to log into the vSphere dashboard.
  • HashiCorp Configuration Language (HCL)
  • the provider credentials are passed in at the top of the script to connect to the vSphere account.
  • modules— a way to encapsulate infrastructure resources into a reusable format.
  • 張 旭 on 28 Mar 19
     
    "revolutionizing"
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