README.MD

   1 # Node Thread Pool :arrow_double_up: :on:
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  11
  12 <h2>Why Poolifier? </h2>
  13 Poolifier is used to perform heavy CPU bound tasks on nodejs servers, it implements thread pools ( yes, more thread pool implementations, so you can choose which one fit better for you ) using <a href="https://nodejs.org/api/worker_threads.html#worker_threads_worker_threads">worker-threads </a>.<br>
  14 With poolifier you can improve your <strong>performance</strong> and resolve problems related to the event loop.<br>
  15 Moreover you can execute your CPU tasks using an API designed to improve the <strong>developer experience</strong>.
  16
  17
  18
  19 <h2>Contents </h2>
  20 <h3 align="center">
  21   <a href="#installation">Installation</a>
  22   <span> · </span>
  23   <a href="#usage">Usage</a>
  24   <span> · </span>
  25   <a href="#api">API</a>
  26   <span> · </span>
  27   <a href="#cyp">Choose a pool</a>
  28   <span> · </span>
  29   <a href="#contribute">Contribute</a>
  30   <span> · </span>
  31   <a href="#nv">Compatibility</a>
  32   <span> · </span>
  33   <a href="#license">License</a>
  34 </h3>
  35
  36 <h2> Overview </h2>
  37 Node pool contains two <a href="https://nodejs.org/api/worker_threads.html#worker_threads_worker_threads">worker-threads </a> pool implementations , you don' t have to deal with worker-threads complexity. <br>
  38 The first implementation is a static thread pool , with a defined number of threads that are started at creation time and will be reused.<br>
  39 The second implementation is a dynamic thread pool with a number of threads started at creation time ( these threads will be always active and reused) and other threads created when the load will increase ( with an upper limit, these threads will be reused when active ), the new created threads will be stopped after a configurable period of inactivity. <br>
  40 You have to implement your worker extending the ThreadWorker class<br>
  41 <h2 id="installation">Installation</h2>
  42
  43 ```
  44 npm install poolifier --save
  45 ```
  46 <h2 id="usage">Usage</h2>
  47
  48 You can implement a worker in a simple way , extending the class ThreadWorker :
  49
  50 ```js
  51 'use strict'
  52 const { ThreadWorker } = require('poolifier')
  53
  54 function yourFunction (data) {
  55   // this will be executed in the worker thread,
  56   // the data will be received by using the execute method
  57   return { ok: 1 }
  58 }
  59
  60 module.exports = new ThreadWorker(yourFunction, { maxInactiveTime: 60000, async: false })
  61 ```
  62
  63 Instantiate your pool based on your needed :
  64
  65 ```js
  66 'use strict'
  67 const { FixedThreadPool, DynamicThreadPool } = require('poolifier')
  68
  69 // a fixed thread pool
  70 const pool = new FixedThreadPool(15,
  71   './yourWorker.js',
  72   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  73
  74 // or a dynamic thread pool
  75 const pool = new DynamicThreadPool(10, 100,
  76   './yourWorker.js',
  77   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  78
  79 pool.emitter.on('FullPool', () => console.log('Pool is full'))
  80
  81 // the execute method signature is the same for both implementations,
  82 // so you can easy switch from one to another
  83 pool.execute({}).then(res => {
  84   console.log(res)
  85 }).catch ....
  86
  87 ```
  88
  89 <strong> See examples folder for more details( in particular if you want to use a pool for [multiple functions](./examples/multiFunctionExample.js) ).</strong>
  90 <strong>Now type script is also supported, find how to use it into the example folder </strong>
  91
  92 <h2 id="nv">Node versions</h2>
  93
  94 You can use node versions 12.x , 13.x, 14.x <br>
  95
  96 <h2 id="api">API</h2>
  97
  98 ### `pool = new FixedThreadPool(numThreads, filePath, opts)`
  99 `numThreads` (mandatory) Num of threads for this worker pool <br>
 100 `filePath` (mandatory) Path to a file with a worker implementation <br>
 101 `opts` (optional) An object with these properties :
 102 - `errorHandler` - A function that will listen for error event on each worker thread
 103 - `onlineHandler` - A function that will listen for online event on each worker thread
 104 - `exitHandler` - A function that will listen for exit event on each worker thread
 105 - `maxTasks` - This is just to avoid not useful warnings message, is used to set <a href="https://nodejs.org/dist/latest-v12.x/docs/api/events.html#events_emitter_setmaxlisteners_n">maxListeners</a> on event emitters ( workers are event emitters)
 106
 107 ### `pool = new DynamicThreadPool(min, max, filePath, opts)`
 108 `min` (mandatory) Same as FixedThreadPool numThreads , this number of threads will be always active <br>
 109 `max` (mandatory) Max number of workers that this pool can contain, the new created threads will die after a threshold ( default is 1 minute , you can override it in your worker implementation). <br>
 110 `filePath` (mandatory) Same as FixedThreadPool  <br>
 111 `opts` (optional) Same as FixedThreadPool <br>
 112
 113 ### `pool.execute(data)`
 114 Execute method is available on both pool implementations ( return type : Promise): <br>
 115 `data` (mandatory) An object that you want to pass to your worker implementation <br>
 116
 117 ### `pool.destroy()`
 118 Destroy method is available on both pool implementations.<br>
 119 This method will call the terminate method on each worker.
 120
 121
 122 ### `class YourWorker extends ThreadWorker`
 123 `fn` (mandatory) The function that you want to execute on the worker thread <br>
 124 `opts` (optional) An object with these properties :
 125 - `maxInactiveTime` - Max time to wait tasks to work on ( in ms) , after this period the new worker threads will die.
 126 - `async` - true/false , true if your function contains async pieces else false
 127
 128 <h2 id="cyp">Choose your pool</h2>
 129 Performance is one of the main target of these thread pool implementations, we want to have a strong focus on this.<br>
 130 We already have a bench folder where you can find some comparisons.
 131 To choose your pool consider that with a FixedThreadPool or a DynamicThreadPool ( in this case is important the min parameter passed to the constructor) your application memory footprint will increase . <br>
 132 Increasing the memory footprint, your application will be ready to accept more CPU bound tasks, but during idle time your application will consume more memory. <br>
 133 One good choose from my point of view is to profile your application using Fixed/Dynamic thread pool , and to see your application metrics when you increase/decrease the num of threads. <br>
 134 For example you could keep the memory footprint low choosing a DynamicThreadPool with 5 threads, and allow to create new threads until 50/100 when needed, this is the advantage to use the DynamicThreadPool. <br>
 135 But in general , <strong>always profile your application </strong>
 136
 137 <h2 id="contribute">Contribute</h2>
 138
 139 See guidelines [CONTRIBUTING](CONTRIBUTING.md) <br>
 140 Choose your task here <a href="https://github.com/pioardi/poolifier/projects/1"> 2.0.0</a>, propose an idea, a fix, an improvement. <br>
 141
 142
 143 <h2 id="license">License</h2>
 144
 145 [MIT](./LICENSE)