README.md

   1 # Node Thread Pool :arrow_double_up: :on:
   2
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  11
  12 ## Why Poolifier?
  13
  14 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 [worker-threads](https://nodejs.org/api/worker_threads.html#worker_threads_worker_threads).
  15 With poolifier you can improve your **performance** and resolve problems related to the event loop.
  16 Moreover you can execute your CPU tasks using an API designed to improve the **developer experience**.
  17
  18 ## Contents
  19
  20 <h3 align="center">
  21   <a href="#overview">Overview</a>
  22   <span> · </span>
  23   <a href="#installation">Installation</a>
  24   <span> · </span>
  25   <a href="#usage">Usage</a>
  26   <span> · </span>
  27   <a href="#node-versions">  Node versions</a>
  28   <span> · </span>
  29   <a href="#api">API</a>
  30   <span> · </span>
  31   <a href="#choose-your-pool">Choose your pool</a>
  32   <span> · </span>
  33   <a href="#contribute">Contribute</a>
  34   <span> · </span>
  35   <a href="#team">Team</a>
  36   <span> · </span>
  37   <a href="#license">License</a>
  38 </h3>
  39
  40 ## Overview
  41
  42 Node pool contains two [worker-threads](https://nodejs.org/api/worker_threads.html#worker_threads_worker_threads) pool implementations, you don't have to deal with worker-threads complexity.
  43 The first implementation is a static thread pool, with a defined number of threads that are started at creation time and will be reused.
  44 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.
  45 You have to implement your worker extending the ThreadWorker class
  46
  47 ## Installation
  48
  49 ```shell
  50 npm install poolifier --save
  51 ```
  52
  53 ## Usage
  54
  55 You can implement a worker in a simple way, extending the class ThreadWorker:
  56
  57 ```js
  58 'use strict'
  59 const { ThreadWorker } = require('poolifier')
  60
  61 function yourFunction (data) {
  62   // this will be executed in the worker thread,
  63   // the data will be received by using the execute method
  64   return { ok: 1 }
  65 }
  66
  67 module.exports = new ThreadWorker(yourFunction, {
  68   maxInactiveTime: 60000,
  69   async: false
  70 })
  71 ```
  72
  73 Instantiate your pool based on your needed :
  74
  75 ```js
  76 'use strict'
  77 const { FixedThreadPool, DynamicThreadPool } = require('poolifier')
  78
  79 // a fixed thread pool
  80 const pool = new FixedThreadPool(15,
  81   './yourWorker.js',
  82   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  83
  84 // or a dynamic thread pool
  85 const pool = new DynamicThreadPool(10, 100,
  86   './yourWorker.js',
  87   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
  88
  89 pool.emitter.on('FullPool', () => console.log('Pool is full'))
  90
  91 // the execute method signature is the same for both implementations,
  92 // so you can easy switch from one to another
  93 pool.execute({}).then(res => {
  94   console.log(res)
  95 }).catch ....
  96
  97 ```
  98
  99 **See examples folder for more details (in particular if you want to use a pool for [multiple functions](./examples/multiFunctionExample.js)).**
 100 **Now type script is also supported, find how to use it into the example folder**
 101
 102 ## Node versions
 103
 104 You can use node versions 12.x, 13.x, 14.x
 105
 106 ## API
 107
 108 ### `pool = new FixedThreadPool(numThreads, filePath, opts)`
 109
 110 `numThreads` (mandatory) Num of threads for this worker pool
 111 `filePath` (mandatory) Path to a file with a worker implementation
 112 `opts` (optional) An object with these properties :
 113
 114 - `errorHandler` - A function that will listen for error event on each worker thread
 115 - `onlineHandler` - A function that will listen for online event on each worker thread
 116 - `exitHandler` - A function that will listen for exit event on each worker thread
 117 - `maxTasks` - This is just to avoid not useful warnings message, is used to set [maxListeners](https://nodejs.org/dist/latest-v12.x/docs/api/events.html#events_emitter_setmaxlisteners_n) on event emitters (workers are event emitters)
 118
 119 ### `pool = new DynamicThreadPool(min, max, filePath, opts)`
 120
 121 `min` (mandatory) Same as FixedThreadPool numThreads, this number of threads will be always active
 122 `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).
 123 `filePath` (mandatory) Same as FixedThreadPool
 124 `opts` (optional) Same as FixedThreadPool
 125
 126 ### `pool.execute(data)`
 127
 128 Execute method is available on both pool implementations (return type : Promise):
 129 `data` (mandatory) An object that you want to pass to your worker implementation
 130
 131 ### `pool.destroy()`
 132
 133 Destroy method is available on both pool implementations.
 134 This method will call the terminate method on each worker.
 135
 136 ### `class YourWorker extends ThreadWorker`
 137
 138 `fn` (mandatory) The function that you want to execute on the worker thread
 139 `opts` (optional) An object with these properties:
 140
 141 - `maxInactiveTime` - Max time to wait tasks to work on ( in ms) , after this period the new worker threads will die.
 142 - `async` - true/false, true if your function contains async pieces else false
 143
 144 ## Choose your pool
 145
 146 Performance is one of the main target of these thread pool implementations, we want to have a strong focus on this.
 147 We already have a bench folder where you can find some comparisons.
 148 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.
 149 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.
 150 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.
 151 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.
 152 But in general, **always profile your application**
 153
 154 ## Contribute
 155
 156 See guidelines [CONTRIBUTING](CONTRIBUTING.md)
 157 Choose your task here [2.0.0](https://github.com/pioardi/poolifier/projects/1), propose an idea, a fix, an improvement.
 158
 159 ## Team
 160
 161 <!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
 162 <!-- prettier-ignore-start -->
 163 <!-- markdownlint-disable -->
 164
 165 **Creator/Owner:**
 166
 167 - [**Alessandro Pio Ardizio**](https://github.com/pioardi)
 168
 169 **_Contributors_**
 170
 171 - [**Shinigami92**](https://github.com/Shinigami92)
 172 - [**Jérôme Benoit**](https://github.com/jerome-benoit)
 173
 174 ## License
 175
 176 [MIT](./LICENSE)