README.MD

   1 # Node Thread Pool :arrow_double_up: :on:
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  10
  11 <h2>Why Poolifier? </h2>
  12 Poolifier is used to perform heavy CPU bound tasks on nodejs servers, it implements a thread pool using <a href="https://nodejs.org/api/worker_threads.html#worker_threads_worker_threads">worker-threads </a>.
  13 With poolifier you can improve your performance and resolve problems related to the event loop.<br>
  14
  15
  16
  17 <h2>Contents </h2>
  18 <h3 align="center">
  19   <a href="#installation">Installation</a>
  20   <span> · </span>
  21   <a href="#usage">Usage</a>
  22   <span> · </span>
  23   <a href="#api">API</a>
  24   <span> · </span>
  25   <a href="#cyp">Choose a pool</a>
  26   <span> · </span>
  27   <a href="#contribute">Contribute</a>
  28   <span> · </span>
  29   <a href="#nv">Compatibility</a>
  30   <span> · </span>
  31   <a href="#license">License</a>
  32 </h3>
  33
  34 <h2> Overview </h2>
  35 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>
  36 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>
  37 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>
  38 You have to implement your worker extending the ThreadWorker class<br>
  39 <h2 id="installation">Installation</h2>
  40
  41 ```
  42 npm install poolifier --save
  43 ```
  44 <h2 id="usage">Usage</h2>
  45
  46 You can implement a worker in a simple way , extending the class ThreadWorker :
  47
  48 ```js
  49 'use strict'
  50 const { ThreadWorker } = require('poolifier')
  51
  52 function yourFunction (data) {
  53   // this will be executed in the worker thread,
  54   // the data will be received by using the execute method
  55   return { ok: 1 }
  56 }
  57
  58 module.exports = new ThreadWorker(yourFunction, { maxInactiveTime: 60000 })
  59 ```
  60
  61 Instantiate your pool based on your needed :
  62
  63 ```js
  64 'use strict'
  65 const { FixedThreadPool, DynamicThreadPool } = require('poolifier')
  66
  67 // a fixed thread pool
  68 const pool = new FixedThreadPool(15,
  69   './yourWorker.js',
  70   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  71
  72 // or a dynamic thread pool
  73 const pool = new DynamicThreadPool(10, 100,
  74   './yourWorker.js',
  75   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  76
  77 pool.emitter.on('FullPool', () => console.log('Pool is full'))
  78
  79 // the execute method signature is the same for both implementations,
  80 // so you can easy switch from one to another
  81 pool.execute({}).then(res => {
  82   console.log(res)
  83 }).catch ....
  84
  85 ```
  86
  87 <strong> See examples folder for more details ( in particular if you want to use a pool for [multiple functions](./examples/multiFunctionExample.js) ).</strong>
  88
  89 <h2 id="nv">Node versions</h2>
  90
  91 You can use node versions 12.x , 13.x  <br>
  92
  93 <h2 id="api">API</h2>
  94
  95 ### `pool = new FixedThreadPool(numThreads, filePath, opts)`
  96 `numThreads` (mandatory) Num of threads for this worker pool <br>
  97 `filePath` (mandatory) Path to a file with a worker implementation <br>
  98 `opts` (optional) An object with these properties :
  99 - `errorHandler` - A function that will listen for error event on each worker thread
 100 - `onlineHandler` - A function that will listen for online event on each worker thread
 101 - `exitHandler` - A function that will listen for exit event on each worker thread
 102 - `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)
 103
 104 ### `pool = new DynamicThreadPool(min, max, filePath, opts)`
 105 `min` (mandatory) Same as FixedThreadPool numThreads , this number of threads will be always active <br>
 106 `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>
 107 `filePath` (mandatory) Same as FixedThreadPool  <br>
 108 `opts` (optional) Same as FixedThreadPool <br>
 109
 110 ### `pool.execute(data)`
 111 Execute method is available on both pool implementations ( return type : Promise): <br>
 112 `data` (mandatory) An object that you want to pass to your worker implementation <br>
 113
 114 ### `pool.destroy()`
 115 Destroy method is available on both pool implementations.<br>
 116 This method will call the terminate method on each worker.
 117
 118
 119 ### `class YourWorker extends ThreadWorker`
 120 `fn` (mandatory) The function that you want to execute on the worker thread <br>
 121 `opts` (optional) An object with these properties :
 122 - `maxInactiveTime` - Max time to wait tasks to work on ( in ms) , after this period the new worker threads will die.
 123
 124 <h2 id="cyp">Choose your pool</h2>
 125 Performance is one of the main target of these thread pool implementations, we want to have a strong focus on this.<br>
 126 We already have a bench folder where you can find some comparisons.
 127 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>
 128 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>
 129 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>
 130 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>
 131 But in general , <strong>always profile your application </strong>
 132
 133 <h2 id="contribute">Contribute</h2>
 134
 135 See guidelines [CONTRIBUTING](CONTRIBUTING.md)
 136
 137
 138 <h2 id="license">License</h2>
 139
 140 [MIT](./LICENSE)