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crazylion lee

p-e-w/maybe: :rabbit2: See what a program does before deciding whether you really want ... - 0 views

github.com/maybe

python Linux sysadmin

shared by crazylion lee on 19 Mar 16 - No Cached
  • crazylion lee on 19 Mar 16
     
    "See what a program does before deciding whether you really want it to happen."
張 旭

Boosting your kubectl productivity ♦︎ Learnk8s - 0 views

learnk8s.io/...kubectl-productivity

devops kubernetes kubectl

shared by 張 旭 on 09 Apr 19 - No Cached
  • kubectl is your cockpit to control Kubernetes.
  • kubectl is a client for the Kubernetes API
  • Kubernetes API is an HTTP REST API.
  • ...75 more annotations...
  • This API is the real Kubernetes user interface.
  • Kubernetes is fully controlled through this API
  • every Kubernetes operation is exposed as an API endpoint and can be executed by an HTTP request to this endpoint.
  • the main job of kubectl is to carry out HTTP requests to the Kubernetes API
  • Kubernetes maintains an internal state of resources, and all Kubernetes operations are CRUD operations on these resources.
  • Kubernetes is a fully resource-centred system
  • Kubernetes API reference is organised as a list of resource types with their associated operations.
  • This is how kubectl works for all commands that interact with the Kubernetes cluster.
  • kubectl simply makes HTTP requests to the appropriate Kubernetes API endpoints.
  • it's totally possible to control Kubernetes with a tool like curl by manually issuing HTTP requests to the Kubernetes API.
  • Kubernetes consists of a set of independent components that run as separate processes on the nodes of a cluster.
  • components on the master nodes
  • Storage backend: stores resource definitions (usually etcd is used)
  • API server: provides Kubernetes API and manages storage backend
  • Controller manager: ensures resource statuses match specifications
  • Scheduler: schedules Pods to worker nodes
  • component on the worker nodes
  • Kubelet: manages execution of containers on a worker node
  • triggers the ReplicaSet controller, which is a sub-process of the controller manager.
  • the scheduler, who watches for Pod definitions that are not yet scheduled to a worker node.
  • creating and updating resources in the storage backend on the master node.
  • The kubelet of the worker node your ReplicaSet Pods have been scheduled to instructs the configured container runtime (which may be Docker) to download the required container images and run the containers.
  • Kubernetes components (except the API server and the storage backend) work by watching for resource changes in the storage backend and manipulating resources in the storage backend.
  • However, these components do not access the storage backend directly, but only through the Kubernetes API.
    • 張 旭
      張 旭 on 09 Apr 19
       
      很精彩，相互之間都是使用 API call 溝通，良好的微服務行為。
  • double usage of the Kubernetes API for internal components as well as for external users is a fundamental design concept of Kubernetes.
  • All other Kubernetes components and users read, watch, and manipulate the state (i.e. resources) of Kubernetes through the Kubernetes API
  • The storage backend stores the state (i.e. resources) of Kubernetes.
  • command completion is a shell feature that works by the means of a completion script.
  • A completion script is a shell script that defines the completion behaviour for a specific command. Sourcing a completion script enables completion for the corresponding command.
  • kubectl completion zsh
  • /etc/bash_completion.d directory (create it, if it doesn't exist)
  • source <(kubectl completion bash)
  • source <(kubectl completion zsh)
  • autoload -Uz compinit compinit
  • the API reference, which contains the full specifications of all resources.
  • kubectl api-resources
  • displays the resource names in their plural form (e.g. deployments instead of deployment). It also displays the shortname (e.g. deploy) for those resources that have one. Don't worry about these differences. All of these name variants are equivalent for kubectl.
  • .spec
  • custom columns output format comes in. It lets you freely define the columns and the data to display in them. You can choose any field of a resource to be displayed as a separate column in the output
  • kubectl get pods -o custom-columns='NAME:metadata.name,NODE:spec.nodeName'
  • kubectl explain pod.spec.
  • kubectl explain pod.metadata.
  • browse the resource specifications and try it out with any fields you like!
  • JSONPath is a language to extract data from JSON documents (it is similar to XPath for XML).
  • with kubectl explain, only a subset of the JSONPath capabilities is supported
  • Many fields of Kubernetes resources are lists, and this operator allows you to select items of these lists. It is often used with a wildcard as [*] to select all items of the list.
  • kubectl get pods -o custom-columns='NAME:metadata.name,IMAGES:spec.containers[*].image'
  • a Pod may contain more than one container.
  • The availability zones for each node are obtained through the special failure-domain.beta.kubernetes.io/zone label.
  • kubectl get nodes -o yaml kubectl get nodes -o json
  • The default kubeconfig file is ~/.kube/config
  • with multiple clusters, then you have connection parameters for multiple clusters configured in your kubeconfig file.
  • Within a cluster, you can set up multiple namespaces (a namespace is kind of "virtual" clusters within a physical cluster)
  • overwrite the default kubeconfig file with the --kubeconfig option for every kubectl command.
  • Namespace: the namespace to use when connecting to the cluster
  • a one-to-one mapping between clusters and contexts.
  • When kubectl reads a kubeconfig file, it always uses the information from the current context.
  • just change the current context in the kubeconfig file
  • to switch to another namespace in the same cluster, you can change the value of the namespace element of the current context
  • kubectl also provides the --cluster, --user, --namespace, and --context options that allow you to overwrite individual elements and the current context itself, regardless of what is set in the kubeconfig file.
  • for switching between clusters and namespaces is kubectx.
  • kubectl config get-contexts
  • just have to download the shell scripts named kubectl-ctx and kubectl-ns to any directory in your PATH and make them executable (for example, with chmod +x)
  • kubectl proxy
  • kubectl get roles
  • kubectl get pod
  • Kubectl plugins are distributed as simple executable files with a name of the form kubectl-x. The prefix kubectl- is mandatory,
  • To install a plugin, you just have to copy the kubectl-x file to any directory in your PATH and make it executable (for example, with chmod +x)
  • krew itself is a kubectl plugin
  • check out the kubectl-plugins GitHub topic
  • The executable can be of any type, a Bash script, a compiled Go program, a Python script, it really doesn't matter. The only requirement is that it can be directly executed by the operating system.
  • kubectl plugins can be written in any programming or scripting language.
  • you can write more sophisticated plugins with real programming languages, for example, using a Kubernetes client library. If you use Go, you can also use the cli-runtime library, which exists specifically for writing kubectl plugins.
  • a kubeconfig file consists of a set of contexts
  • changing the current context means changing the cluster, if you have only a single context per cluster.
crazylion lee

GitHub - gurugio/lowlevelprogramming-university: How to be low-level programmer - 0 views

github.com/...lowlevelprogramming-university

programming low level

shared by crazylion lee on 16 Apr 17 - No Cached
  • crazylion lee on 16 Apr 17
     
    " Low-Level Programming University"
張 旭

Deploy Replica Set With Keyfile Authentication - MongoDB Manual - 0 views

docs.mongodb.com/...et-with-keyfile-access-control

database mongodb

shared by 張 旭 on 13 Oct 20 - No Cached
  • Keyfiles are bare-minimum forms of security and are best suited for testing or development environments.
  • With keyfile authentication, each mongod instances in the replica set uses the contents of the keyfile as the shared password for authenticating other members in the deployment.
  • On UNIX systems, the keyfile must not have group or world permissions.
  • ...3 more annotations...
  • Copy the keyfile to each server hosting the replica set members.
  • the user running the mongod instances is the owner of the file and can access the keyfile.
  • For each member in the replica set, start the mongod with either the security.keyFile configuration file setting or the --keyFile command-line option.
張 旭

Gracefully Shutdown Docker Container - Kakashi's Blog - 1 views

kkc.github.io/...ully-shutdown-docker-container

docker process nodejs

shared by 張 旭 on 17 Nov 20 - No Cached
  • The initial idea is to make application invokes deconstructor of each component as soon as the application receives specific signals such as SIGTERM and SIGINT
  • When you run a docker container, by default it has a PID namespace, which means the docker process is isolated from other processes on your host.
  • The PID namespace has an important task to reap zombie processes.
  • ...11 more annotations...
  • This uses /bin/bash as PID1 and runs your program as the subprocess.
  • When a signal is sent to a shell, the signal actually won’t be forwarded to subprocesses.
  • By using the exec form, we can run our program as PID1
  • if you use exec form to run a shell script to spawn your application, remember to use exec syscall to overwrite /usr/bin/bash otherwise it will act as senario1
  • /bin/bash can handle repeating zombie process
  • with Tini, SIGTERM properly terminates your process even if you didn’t explicitly install a signal handler for it.
  • run tini as PID1 and it will forward the signal for subprocesses.
  • tini is a signal proxy and it also can deal with zombie process issue automatically.
  • run your program with tini by passing --init flag to docker run
  • use docker stop, docker will wait for 10s for stopping container before killing a process (by default). The main process inside the container will receive SIGTERM, then docker daemon will wait for 10s and send SIGKILL to terminate process.
  • kill running containers immediately. it’s more like kill -9 and kill --SIGKILL
張 旭

architecture - Difference between a "coroutine" and a "thread"? - Stack Overflow - 0 views

stackoverflow.com/...tween-a-coroutine-and-a-thread

programming

shared by 張 旭 on 09 Jun 22 - No Cached
  • Co stands for cooperation. A co routine is asked to (or better expected to) willingly suspend its execution to give other co-routines a chance to execute too. So a co-routine is about sharing CPU resources (willingly) so others can use the same resource as oneself is using.
  • A thread on the other hand does not need to suspend its execution. Being suspended is completely transparent to the thread and the thread is forced by underlying hardware to suspend itself.
  • co-routines can not be concurrently executed and race conditions can not occur.
  • ...8 more annotations...
  • Concurrency is the separation of tasks to provide interleaved execution.
  • Parallelism is the simultaneous execution of multiple pieces of work in order to increase speed.
  • With threads, the operating system switches running threads preemptively according to its scheduler, which is an algorithm in the operating system kernel.
  • With coroutines, the programmer and programming language determine when to switch coroutines
  • In contrast to threads, which are pre-emptively scheduled by the operating system, coroutine switches are cooperative, meaning the programmer (and possibly the programming language and its runtime) controls when a switch will happen.
  • preemption
  • Coroutines are a form of sequential processing: only one is executing at any given time
  • Threads are (at least conceptually) a form of concurrent processing: multiple threads may be executing at any given time.
  • 張 旭 on 09 Jun 22
     
    "Co stands for cooperation. A co routine is asked to (or better expected to) willingly suspend its execution to give other co-routines a chance to execute too. So a co-routine is about sharing CPU resources (willingly) so others can use the same resource as oneself is using."
crazylion lee

Puck.js - the JavaScript Bluetooth Beacon - 0 views

www.puck-js.com/?utm_source=javascriptweekly&utm_medium=email

javascript bluetooth beacon

shared by crazylion lee on 15 Jul 16 - No Cached
  • crazylion lee on 15 Jul 16
     
    "The ground-breaking bluetooth beacon - An Open Source JavaScript microcontroller you can program wirelessly. No software needed so get started in seconds."
crazylion lee

README - md2man - 0 views

sunaku.github.io/...README.html

readme man markdown

shared by crazylion lee on 26 Mar 16 - No Cached
  • crazylion lee on 26 Mar 16
     
    "md2man is a Ruby library and a set of command-line programs that convert Markdown into UNIX manpages as well as HTML webpages using Redcarpet."
crazylion lee

TMSU - 0 views

tmsu.org

filesystem linux tag file tagging

shared by crazylion lee on 27 Jun 16 - No Cached
  • crazylion lee on 27 Jun 16
     
    "TMSU is a tool for tagging your files. It provides a simple command-line tool for applying tags and a virtual filesystem so that you can get a tag-based view of your files from within any other program. TMSU does not alter your files in any way: they remain unchanged on disk, or on the network, wherever you put them. TMSU maintains its own database and you simply gain an additional view, which you can mount, based upon the tags you set up. The only commitment required is your time and there's absolutely no lock-in."
張 旭

I am a puts debuggerer | Tenderlovemaking - 0 views

tenderlovemaking.com/...i-am-a-puts-debuggerer.html

ruby programming debug rails

shared by 張 旭 on 22 Feb 17 - No Cached
  • method(:render).source_location
  • method(:render).super_method.source_location
  • unbind the method from Kernel, rebind it to the request
  • ...9 more annotations...
  • The TracePoint allocated here will fire on every “call” event and the block will print out the method name and location of the call.
  • The -d flag will enable warnings and also print out every line where an exception was raised.
  • re-raised
  • RUBYOPT=-d bundle exec rake test
  • The RUBYOPT environment variable will get applied to every Ruby program that is executed in this shell, even sub shells executed by rake.
  • @sharing.freeze
  • can't modify frozen Hash
  • where the first mutation happened
  • I hit Ctrl-T (sorry, this only works on OS X, you’ll need to use kill on Linux
crazylion lee

Gobot - 0 views

gobot.io

go robot automator

shared by crazylion lee on 17 Jan 14 - No Cached
  • crazylion lee on 17 Jan 14
     
    Gobot is set of libraries in the Go programming language for robotics and physical computing. It provides a simple, yet powerful way to create solutions that incorporate multiple, different hardware devices at the same time. Want to use Ruby on robots? Check out our sister project Artoo (http://artoo.io). Want to use Node.js? Check out our sister project Cylon (http://cylonjs.com).
crazylion lee

EntilZha/ScalaFunctional - 0 views

github.com/...ScalaFunctional

python pipeline linq

shared by crazylion lee on 23 Nov 15 - No Cached
  • crazylion lee on 23 Nov 15
     
    "Python library for creating working with data in a pipeline/LINQ/functional programming way"
張 旭

Sorting for Humans : Natural Sort Order - 0 views

blog.codinghorror.com/-for-humans-natural-sort-order

python programming sort file

shared by 張 旭 on 07 Dec 18 - No Cached
  • It's a completely nonsensical ordering to anyone who doesn't have the ASCII chart committed to memory (and by the way, uppercase A is decimal 65).
  • it's hard to find information on natural sorting
  • Implementing a natural sort is more complex than it seems
  • ...3 more annotations...
  • a basic natural sort shouldn't require the 40+ lines of code it takes in most languages.
  • ASCIIbetical does not equal alphabetical
  • a more human-friendly natural sort option should be built into mainstream programming languages
張 旭

drapergem/draper: Decorators/View-Models for Rails Applications - 0 views

github.com/draper

rails model programming decorator

shared by 張 旭 on 04 Jul 17 - No Cached
  • The decorator wraps the model, and deals only with presentational concerns.
  • In the controller, you decorate the article before handing it off to the view
  • whenever you start needing logic in the view or start thinking about a helper method, you can implement a method on the decorator instead.
  • ...5 more annotations...
  • convert an existing Rails helper to a decorator method
  • That method is presentation-centric, and thus does not belong in a model.
  • Where does that come from? It's a method of the source Article, whose methods have been made available on the decorator by the delegate_all call above.
  • a great way to replace procedural helpers like the one above with "real" object-oriented programming
  • format complex data for user display
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
crazylion lee

Cello * High Level C - 0 views

libcello.org

c library high level

shared by crazylion lee on 16 Apr 17 - No Cached
  • crazylion lee on 16 Apr 17
     
    "Cello is a library that brings higher level programming to C. By acting as a modern, powerful runtime system Cello makes many things easy that were previously impractical or awkward in C such as: Generic Data Structures Polymorphic Functions Interfaces / Type Classes Constructors / Destructors Optional Garbage Collection Exceptions Reflection And because Cello works seamlessly alongside standard C you get all the other benefits such as great performance, powerful tooling, and extensive libraries."
張 旭

Database Profiler - MongoDB Manual - 0 views

docs.mongodb.com/...manage-the-database-profiler

database mongodb

shared by 張 旭 on 16 Apr 21 - No Cached
  • The database profiler collects detailed information about Database Commands executed against a running mongod instance.
  • The profiler writes all the data it collects to the system.profile collection, a capped collection in the admin database.
  • db.setProfilingLevel(2)
  • ...10 more annotations...
  • The slowms and sampleRate profiling settings are global. When set, these settings affect all databases in your process.
  • db.setProfilingLevel(1, { slowms: 20 })
  • db.setProfilingLevel(0, { slowms: 20 })
  • show profile
  • The system.profile collection is a capped collection with a default size of 1 megabyte.
  • By default, sampleRate is set to 1.0, meaning all slow operations are profiled.
  • When logLevel is set to 0, MongoDB records slow operations to the diagnostic log at a rate determined by slowOpSampleRate.
  • The slowms field indicates operation time threshold, in milliseconds, beyond which operations are considered slow.
  • You cannot enable profiling on a mongos instance.
  • profiler logs information about database operations in the system.profile collection.
張 旭

MongoDB Performance - MongoDB Manual - 0 views

docs.mongodb.com/...analyzing-mongodb-performance

database mongodb performance

shared by 張 旭 on 20 Apr 21 - No Cached
  • MongoDB uses a locking system to ensure data set consistency. If certain operations are long-running or a queue forms, performance will degrade as requests and operations wait for the lock.
  • performance limitations as a result of inadequate or inappropriate indexing strategies, or as a consequence of poor schema design patterns.
  • performance issues may be temporary and related to abnormal traffic load.
  • ...9 more annotations...
  • Lock-related slowdowns can be intermittent.
  • If globalLock.currentQueue.total is consistently high, then there is a chance that a large number of requests are waiting for a lock.
  • If globalLock.totalTime is high relative to uptime, the database has existed in a lock state for a significant amount of time.
  • For write-heavy applications, deploy sharding and add one or more shards to a sharded cluster to distribute load among mongod instances.
  • Unless constrained by system-wide limits, the maximum number of incoming connections supported by MongoDB is configured with the maxIncomingConnections setting.
  • When logLevel is set to 0, MongoDB records slow operations to the diagnostic log at a rate determined by slowOpSampleRate.
  • At higher logLevel settings, all operations appear in the diagnostic log regardless of their latency with the following exception
  • Full Time Diagnostic Data Collection (FTDC) mechanism. FTDC data files are compressed, are not human-readable, and inherit the same file access permissions as the MongoDB data files.
  • mongod processes store FTDC data files in a diagnostic.data directory under the instances storage.dbPath.
  • 張 旭 on 20 Apr 21
     
    "MongoDB uses a locking system to ensure data set consistency. If certain operations are long-running or a queue forms, performance will degrade as requests and operations wait for the lock."
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