README.MD

   1 # Node Thread Pool :arrow_double_up: :on:
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  10
  11 <h2>Contents </h2>
  12 <h3 align="center">
  13   <a href="#installation">Installation</a>
  14   <span> · </span>
  15   <a href="#usage">Usage</a>
  16   <span> · </span>
  17   <a href="#api">API</a>
  18   <span> · </span>
  19   <a href="#cyp">Choose a pool</a>
  20   <span> · </span>
  21   <a href="#contribute">Contribute</a>
  22   <span> · </span>
  23   <a href="#nv">Compatibility</a>
  24   <span> · </span>
  25   <a href="#license">License</a>
  26 </h3>
  27
  28 <h2> Overview </h2>
  29 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>
  30 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>
  31 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>
  32 You have to implement your worker extending the ThreadWorker class<br>
  33 <h2 id="installation">Installation</h2>
  34
  35 ```
  36 npm install node-thread-pool --save
  37 ```
  38 <h2 id="usage">Usage</h2>
  39
  40 You can implement a worker in a simple way , extending the class ThreadWorker :
  41
  42 ```js
  43 'use strict'
  44 const { ThreadWorker } = require('node-pool')
  45
  46 function yourFunction (data) {
  47   // this will be executed in the worker thread,
  48   // the data will be received by using the execute method
  49   return { ok: 1 }
  50 }
  51
  52 class MyWorker extends ThreadWorker {
  53   constructor () {
  54     super(yourFunction, { maxInactiveTime: 1000 * 60})
  55   }
  56 }
  57 module.exports = new MyWorker()
  58 ```
  59
  60 Instantiate your pool based on your needed :
  61
  62 ```js
  63 'use strict'
  64 const { FixedThreadPool, DynamicThreadPool } = require('node-pool')
  65
  66 // a fixed thread pool
  67 const pool = new FixedThreadPool(15,
  68   './yourWorker.js',
  69   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  70
  71 // or a dynamic thread pool
  72 const pool = new DynamicThreadPool(10, 100,
  73   './yourWorker.js',
  74   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  75
  76 pool.emitter.on('FullPool', () => console.log('Pool is full'))
  77
  78 // the execute method signature is the same for both implementations,
  79 // so you can easy switch from one to another
  80 pool.execute({}).then(res => {
  81   console.log(res)
  82 }).catch ....
  83
  84 ```
  85
  86 <strong> See examples folder for more details ( in particular if you want to use a pool for [multiple functions](./examples/multiFunctionExample.js) ).</strong>
  87
  88 <h2 id="nv">Node versions</h2>
  89
  90 You can use node versions 12.x , 13.x  <br>
  91
  92 <h2 id="api">API</h2>
  93
  94 ### `pool = new FixedThreadPool(numThreads, filePath, opts)`
  95 `numThreads` (mandatory) Num of threads for this worker pool <br>
  96 `filePath` (mandatory) Path to a file with a worker implementation <br>
  97 `opts` (optional) An object with these properties :
  98 - `errorHandler` - A function that will listen for error event on each worker thread
  99 - `onlineHandler` - A function that will listen for online event on each worker thread
 100 - `exitHandler` - A function that will listen for exit event on each worker thread
 101 - `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)
 102
 103 ### `pool = new DynamicThreadPool(min, max, filePath, opts)`
 104 `min` (mandatory) Same as FixedThreadPool numThreads , this number of threads will be always active <br>
 105 `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>
 106 `filePath` (mandatory) Same as FixedThreadPool  <br>
 107 `opts` (optional) Same as FixedThreadPool <br>
 108
 109 ### `pool.execute(data)`
 110 Execute method is available on both pool implementations ( return type : Promise): <br>
 111 `data` (mandatory) An object that you want to pass to your worker implementation <br>
 112
 113 ### `pool.destroy()`
 114 Destroy method is available on both pool implementations.<br>
 115 This method will call the terminate method on each worker.
 116
 117
 118 ### `class YourWorker extends ThreadWorker`
 119 `fn` (mandatory) The function that you want to execute on the worker thread <br>
 120 `opts` (optional) An object with these properties :
 121 - `maxInactiveTime` - Max time to wait tasks to work on ( in ms) , after this period the new worker threads will die.
 122
 123 <h2 id="cyp">Choose your pool</h2>
 124 Performance is one of the main target of these thread pool implementations, we want to have a strong focus on this.<br>
 125 We already have a bench folder where you can find some comparisons.
 126 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>
 127 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>
 128 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>
 129 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>
 130 But in general , <strong>always profile your application </strong>
 131
 132 <h2 id="contribute">Contribute</h2>
 133
 134 See guidelines [CONTRIBUTING](./.github/CONTRIBUTING.md)
 135
 136
 137 <h2 id="license">License</h2>
 138
 139 [MIT](./LICENSE)
 140