README.md

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   4
   5 <h2 align="center">Node Thread Pool :arrow_double_up: :on:</h2>
   6
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  26
  27 </p>
  28
  29
  30
  31
  32 ## Why Poolifier?
  33
  34 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).
  35 With poolifier you can improve your **performance** and resolve problems related to the event loop.
  36 Moreover you can execute your CPU tasks using an API designed to improve the **developer experience**.
  37
  38 - Performance :racehorse:
  39 - Security :bank: :cop: [![Security Rating](https://sonarcloud.io/api/project_badges/measure?project=pioardi_poolifier&metric=security_rating)](https://sonarcloud.io/dashboard?id=pioardi_poolifier) [![Vulnerabilities](https://sonarcloud.io/api/project_badges/measure?project=pioardi_poolifier&metric=vulnerabilities)](https://sonarcloud.io/dashboard?id=pioardi_poolifier)
  40 - Easy to use :couple:
  41 - Easy switch from a pool to another, easy to tune :heavy_check_mark:
  42 - Dynamic pool size :heavy_check_mark:
  43 - No runtime dependencies :heavy_check_mark:
  44 - Proper async integration with node async hooks :heavy_check_mark:
  45 - Support for worker threads and cluster node modules :heavy_check_mark:
  46 - Support sync and async tasks :heavy_check_mark:
  47 - General guidance on pools to use :heavy_check_mark:
  48 - Widely tested :heavy_check_mark:
  49 - Error handling out of the box :heavy_check_mark:
  50 - Active community :heavy_check_mark:
  51 - Code quality :octocat: [![Bugs](https://sonarcloud.io/api/project_badges/measure?project=pioardi_poolifier&metric=bugs)](https://sonarcloud.io/dashboard?id=pioardi_poolifier)
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  57
  58
  59 ## Contents
  60
  61 <h3 align="center">
  62   <a href="#overview">Overview</a>
  63   <span> · </span>
  64   <a href="#installation">Installation</a>
  65   <span> · </span>
  66   <a href="#usage">Usage</a>
  67   <span> · </span>
  68   <a href="#node-versions">  Node versions</a>
  69   <span> · </span>
  70   <a href="#api">API</a>
  71   <span> · </span>
  72   <a href="#choose-your-pool">Choose your pool</a>
  73   <span> · </span>
  74   <a href="#contribute">Contribute</a>
  75   <span> · </span>
  76   <a href="#team">Team</a>
  77   <span> · </span>
  78   <a href="#license">License</a>
  79 </h3>
  80
  81 ## Overview
  82
  83 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.
  84 The first implementation is a static thread pool, with a defined number of threads that are started at creation time and will be reused.
  85 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.
  86 You have to implement your worker extending the ThreadWorker class
  87
  88 ## Installation
  89
  90 ```shell
  91 npm install poolifier --save
  92 ```
  93
  94 ## Usage
  95
  96 You can implement a worker in a simple way, extending the class ThreadWorker:
  97
  98 ```js
  99 'use strict'
 100 const { ThreadWorker } = require('poolifier')
 101
 102 function yourFunction (data) {
 103   // this will be executed in the worker thread,
 104   // the data will be received by using the execute method
 105   return { ok: 1 }
 106 }
 107
 108 module.exports = new ThreadWorker(yourFunction, {
 109   maxInactiveTime: 60000,
 110   async: false
 111 })
 112 ```
 113
 114 Instantiate your pool based on your needed :
 115
 116 ```js
 117 'use strict'
 118 const { FixedThreadPool, DynamicThreadPool } = require('poolifier')
 119
 120 // a fixed thread pool
 121 const pool = new FixedThreadPool(15,
 122   './yourWorker.js',
 123   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
 124
 125 // or a dynamic thread pool
 126 const pool = new DynamicThreadPool(10, 100,
 127   './yourWorker.js',
 128   { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })
 129
 130 pool.emitter.on('FullPool', () => console.log('Pool is full'))
 131
 132 // the execute method signature is the same for both implementations,
 133 // so you can easy switch from one to another
 134 pool.execute({}).then(res => {
 135   console.log(res)
 136 }).catch ....
 137
 138 ```
 139
 140 **See examples folder for more details (in particular if you want to use a pool for [multiple functions](./examples/multiFunctionExample.js)).**
 141 **Now type script is also supported, find how to use it into the example folder**
 142
 143 ## Node versions
 144
 145 You can use node versions 12.x, 13.x, 14.x
 146
 147 ## API
 148
 149 ### `pool = new FixedThreadPool(numThreads, filePath, opts)`
 150
 151 `numThreads` (mandatory) Num of threads for this worker pool
 152 `filePath` (mandatory) Path to a file with a worker implementation
 153 `opts` (optional) An object with these properties :
 154
 155 - `errorHandler` - A function that will listen for error event on each worker thread
 156 - `onlineHandler` - A function that will listen for online event on each worker thread
 157 - `exitHandler` - A function that will listen for exit event on each worker thread
 158 - `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)
 159
 160 ### `pool = new DynamicThreadPool(min, max, filePath, opts)`
 161
 162 `min` (mandatory) Same as FixedThreadPool numThreads, this number of threads will be always active
 163 `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).
 164 `filePath` (mandatory) Same as FixedThreadPool
 165 `opts` (optional) Same as FixedThreadPool
 166
 167 ### `pool.execute(data)`
 168
 169 Execute method is available on both pool implementations (return type : Promise):
 170 `data` (mandatory) An object that you want to pass to your worker implementation
 171
 172 ### `pool.destroy()`
 173
 174 Destroy method is available on both pool implementations.
 175 This method will call the terminate method on each worker.
 176
 177 ### `class YourWorker extends ThreadWorker`
 178
 179 `fn` (mandatory) The function that you want to execute on the worker thread
 180 `opts` (optional) An object with these properties:
 181
 182 - `maxInactiveTime` - Max time to wait tasks to work on ( in ms) , after this period the new worker threads will die.
 183 - `async` - true/false, true if your function contains async pieces else false
 184
 185 ## Choose your pool
 186
 187 Performance is one of the main target of these thread pool implementations, we want to have a strong focus on this.
 188 We already have a bench folder where you can find some comparisons.
 189 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.
 190 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.
 191 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.
 192 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.
 193 But in general, **always profile your application**
 194
 195 ## Contribute
 196
 197 See guidelines [CONTRIBUTING](CONTRIBUTING.md)
 198 Choose your task here [2.0.0](https://github.com/pioardi/poolifier/projects/1), propose an idea, a fix, an improvement.
 199
 200 ## Team
 201
 202 <!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
 203 <!-- prettier-ignore-start -->
 204 <!-- markdownlint-disable -->
 205
 206 **Creator/Owner:**
 207
 208 - [**Alessandro Pio Ardizio**](https://github.com/pioardi)
 209
 210 **_Contributors_**
 211
 212 - [**Shinigami92**](https://github.com/Shinigami92)
 213 - [**Jérôme Benoit**](https://github.com/jerome-benoit)
 214
 215 ## License
 216
 217 [MIT](./LICENSE)