refactor: factor out worker message handlers
[poolifier.git] / README.md
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4
5 <h2 align="center">Node Thread Pool and Cluster Pool :arrow_double_up: :on:</h2>
6
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29
30 ## Why Poolifier?
31
32 Poolifier is used to perform CPU intensive and I/O intensive tasks on nodejs servers, it implements worker pools using [worker-threads](https://nodejs.org/api/worker_threads.html#worker_threads_worker_threads) and cluster pools using [Node.js cluster](https://nodejs.org/api/cluster.html) modules.
33 With poolifier you can improve your **performance** and resolve problems related to the event loop.
34 Moreover you can execute your tasks using an API designed to improve the **developer experience**.
35 Please consult our [general guidelines](#general-guidance).
36
37 - Easy to use :white_check_mark:
38 - Performance [benchmarks](./benchmarks/README.md) :white_check_mark:
39 - Dynamic pool size :white_check_mark:
40 - Easy switch from a pool to another :white_check_mark:
41 - No runtime dependencies :white_check_mark:
42 - Proper async integration with node async hooks :white_check_mark:
43 - Support CommonJS, ESM, and TypeScript :white_check_mark:
44 - Support for worker-threads and cluster node modules :white_check_mark:
45 - Support sync and async tasks :white_check_mark:
46 - Tasks distribution strategies :white_check_mark:
47 - General guidance on pool choice :white_check_mark:
48 - Widely tested :white_check_mark:
49 - Error handling out of the box :white_check_mark:
50 - Active community :white_check_mark:
51 - Code quality [![Bugs](https://sonarcloud.io/api/project_badges/measure?project=pioardi_poolifier&metric=bugs)](https://sonarcloud.io/dashboard?id=pioardi_poolifier)
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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="#general-guidance">General guidance</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)/[cluster worker](https://nodejs.org/api/cluster.html#cluster_class_worker) pool implementations, you don't have to deal with worker-threads/cluster worker complexity.
84 The first implementation is a static worker pool, with a defined number of workers that are started at creation time and will be reused.
85 The second implementation is a dynamic worker pool with a number of worker started at creation time (these workers will be always active and reused) and other workers created when the load will increase (with an upper limit, these workers will be reused when active), the new created workers will be stopped after a configurable period of inactivity.
86 You have to implement your worker by extending the ThreadWorker or ClusterWorker class.
87
88 ## Installation
89
90 ```shell
91 npm install poolifier --save
92 ```
93
94 ## Usage
95
96 You can implement a worker-threads worker in a simple way by 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 })
111 ```
112
113 Instantiate your pool based on your needs :
114
115 ```js
116 'use strict'
117 const { DynamicThreadPool, FixedThreadPool, PoolEvents, availableParallelism } = require('poolifier')
118
119 // a fixed worker-threads pool
120 const pool = new FixedThreadPool(availableParallelism(), './yourWorker.js', {
121 errorHandler: e => console.error(e),
122 onlineHandler: () => console.info('worker is online')
123 })
124
125 pool.emitter.on(PoolEvents.busy, () => console.info('Pool is busy'))
126
127 // or a dynamic worker-threads pool
128 const pool = new DynamicThreadPool(availableParallelism() / 2, availableParallelism(), './yourWorker.js', {
129 errorHandler: e => console.error(e),
130 onlineHandler: () => console.info('worker is online')
131 })
132
133 pool.emitter.on(PoolEvents.full, () => console.info('Pool is full'))
134 pool.emitter.on(PoolEvents.busy, () => console.info('Pool is busy'))
135
136 // the execute method signature is the same for both implementations,
137 // so you can easy switch from one to another
138 pool
139 .execute({})
140 .then(res => {
141 console.info(res)
142 })
143 .catch(err => {
144 console.error(err)
145 })
146 ```
147
148 You can do the same with the classes ClusterWorker, FixedClusterPool and DynamicClusterPool.
149
150 **See [examples](./examples/) folder for more details (in particular if you want to use a pool with [multiple worker functions](./examples/multiFunctionExample.js))**.
151
152 Remember that workers can only send and receive structured-cloneable data.
153
154 ## Node versions
155
156 Node versions >= 16.14.x are supported.
157
158 ## [API](https://poolifier.github.io/poolifier/)
159
160 ### `PoolOptions`
161
162 An object with these properties:
163
164 - `messageHandler` (optional) - A function that will listen for message event on each worker
165 - `errorHandler` (optional) - A function that will listen for error event on each worker
166 - `onlineHandler` (optional) - A function that will listen for online event on each worker
167 - `exitHandler` (optional) - A function that will listen for exit event on each worker
168 - `workerChoiceStrategy` (optional) - The worker choice strategy to use in this pool:
169
170 - `WorkerChoiceStrategies.ROUND_ROBIN`: Submit tasks to worker in a round robin fashion
171 - `WorkerChoiceStrategies.LEAST_USED`: Submit tasks to the worker with the minimum number of executed, executing and queued tasks
172 - `WorkerChoiceStrategies.LEAST_BUSY`: Submit tasks to the worker with the minimum tasks total execution and wait time
173 - `WorkerChoiceStrategies.LEAST_ELU`: Submit tasks to the worker with the minimum event loop utilization (ELU) (experimental)
174 - `WorkerChoiceStrategies.WEIGHTED_ROUND_ROBIN`: Submit tasks to worker by using a [weighted round robin scheduling algorithm](./src/pools/selection-strategies/README.md#weighted-round-robin) based on tasks execution time
175 - `WorkerChoiceStrategies.INTERLEAVED_WEIGHTED_ROUND_ROBIN`: Submit tasks to worker by using an [interleaved weighted round robin scheduling algorithm](./src/pools/selection-strategies/README.md#interleaved-weighted-round-robin) based on tasks execution time(experimental)
176 - `WorkerChoiceStrategies.FAIR_SHARE`: Submit tasks to worker by using a [fair share scheduling algorithm](./src/pools/selection-strategies/README.md#fair-share) based on tasks execution time (the default) or ELU active time
177
178 `WorkerChoiceStrategies.WEIGHTED_ROUND_ROBIN`, `WorkerChoiceStrategies.INTERLEAVED_WEIGHTED_ROUND_ROBIN` and `WorkerChoiceStrategies.FAIR_SHARE` strategies are targeted to heavy and long tasks.
179 Default: `WorkerChoiceStrategies.ROUND_ROBIN`
180
181 - `workerChoiceStrategyOptions` (optional) - The worker choice strategy options object to use in this pool.
182 Properties:
183
184 - `measurement` (optional) - The measurement to use in worker choice strategies: `runTime`, `waitTime` or `elu`.
185 - `runTime` (optional) - Use the tasks [median](./src/pools/selection-strategies/README.md#median) runtime instead of the tasks average runtime in worker choice strategies.
186 - `waitTime` (optional) - Use the tasks [median](./src/pools/selection-strategies/README.md#median) wait time instead of the tasks average wait time in worker choice strategies.
187 - `elu` (optional) - Use the tasks [median](./src/pools/selection-strategies/README.md#median) ELU instead of the tasks average ELU in worker choice strategies.
188 - `weights` (optional) - The worker weights to use in weighted round robin worker choice strategies: `{ 0: 200, 1: 300, ..., n: 100 }`.
189
190 Default: `{ runTime: { median: false }, waitTime: { median: false }, elu: { median: false } }`
191
192 - `restartWorkerOnError` (optional) - Restart worker on uncaught error in this pool.
193 Default: `true`
194 - `enableEvents` (optional) - Events emission enablement in this pool.
195 Default: `true`
196 - `enableTasksQueue` (optional) - Tasks queue per worker enablement in this pool.
197 Default: `false`
198
199 - `tasksQueueOptions` (optional) - The worker tasks queue options object to use in this pool.
200 Properties:
201
202 - `concurrency` (optional) - The maximum number of tasks that can be executed concurrently on a worker.
203
204 Default: `{ concurrency: 1 }`
205
206 #### `ThreadPoolOptions extends PoolOptions`
207
208 - `workerOptions` (optional) - An object with the worker options to pass to worker. See [worker_threads](https://nodejs.org/api/worker_threads.html#worker_threads_new_worker_filename_options) for more details.
209
210 #### `ClusterPoolOptions extends PoolOptions`
211
212 - `env` (optional) - An object with the environment variables to pass to worker. See [cluster](https://nodejs.org/api/cluster.html#cluster_cluster_fork_env) for more details.
213
214 - `settings` (optional) - An object with the cluster settings. See [cluster](https://nodejs.org/api/cluster.html#cluster_cluster_settings) for more details.
215
216 ### `pool = new FixedThreadPool/FixedClusterPool(numberOfThreads/numberOfWorkers, filePath, opts)`
217
218 `numberOfThreads/numberOfWorkers` (mandatory) Number of workers for this pool
219 `filePath` (mandatory) Path to a file with a worker implementation
220 `opts` (optional) An object with the pool options properties described above
221
222 ### `pool = new DynamicThreadPool/DynamicClusterPool(min, max, filePath, opts)`
223
224 `min` (mandatory) Same as FixedThreadPool/FixedClusterPool numberOfThreads/numberOfWorkers, this number of workers will be always active
225 `max` (mandatory) Max number of workers that this pool can contain, the new created workers will die after a threshold (default is 1 minute, you can override it in your worker implementation).
226 `filePath` (mandatory) Path to a file with a worker implementation
227 `opts` (optional) An object with the pool options properties described above
228
229 ### `pool.execute(data, name)`
230
231 `data` (optional) An object that you want to pass to your worker implementation
232 `name` (optional) A string with the task function name that you want to execute on the worker. Default: `'default'`
233 This method is available on both pool implementations and returns a promise.
234
235 ### `pool.destroy()`
236
237 Destroy method is available on both pool implementations.
238 This method will call the terminate method on each worker.
239
240 ### `class YourWorker extends ThreadWorker/ClusterWorker`
241
242 `taskFunctions` (mandatory) The task function or task functions object that you want to execute on the worker
243 `opts` (optional) An object with these properties:
244
245 - `maxInactiveTime` (optional) - Max time to wait tasks to work on in milliseconds, after this period the new worker will die.
246 The last active time of your worker unit will be updated when a task is submitted to a worker or when a worker terminate a task.
247 If `killBehavior` is set to `KillBehaviors.HARD` this value represents also the timeout for the tasks that you submit to the pool, when this timeout expires your tasks is interrupted and the worker is killed if is not part of the minimum size of the pool.
248 If `killBehavior` is set to `KillBehaviors.SOFT` your tasks have no timeout and your workers will not be terminated until your task is completed.
249 Default: `60000`
250
251 - `killBehavior` (optional) - Dictates if your async unit (worker/process) will be deleted in case that a task is active on it.
252 **KillBehaviors.SOFT**: If `currentTime - lastActiveTime` is greater than `maxInactiveTime` but a task is still executing or queued, then the worker **won't** be deleted.
253 **KillBehaviors.HARD**: If `currentTime - lastActiveTime` is greater than `maxInactiveTime` but a task is still executing or queued, then the worker will be deleted.
254 This option only apply to the newly created workers.
255 Default: `KillBehaviors.SOFT`
256
257 ## General guidance
258
259 Performance is one of the main target of these worker pool implementations, we want to have a strong focus on this.
260 We already have a bench folder where you can find some comparisons.
261
262 ### Internal Node.js thread pool
263
264 Before to jump into each poolifier pool type, let highlight that **Node.js comes with a thread pool already**, the libuv thread pool where some particular tasks already run by default.
265 Please take a look at [which tasks run on the libuv thread pool](https://nodejs.org/en/docs/guides/dont-block-the-event-loop/#what-code-runs-on-the-worker-pool).
266
267 **If your task runs on libuv thread pool**, you can try to:
268
269 - Tune the libuv thread pool size setting the [UV_THREADPOOL_SIZE](https://nodejs.org/api/cli.html#cli_uv_threadpool_size_size).
270
271 and/or
272
273 - Use poolifier cluster pool that spawning child processes will also increase the number of libuv threads since that any new child process comes with a separated libuv thread pool. **More threads does not mean more fast, so please tune your application**.
274
275 ### Cluster vs Threads worker pools
276
277 **If your task does not run into libuv thread pool** and is CPU intensive then poolifier **thread pools** (FixedThreadPool and DynamicThreadPool) are suggested to run CPU intensive tasks, you can still run I/O intensive tasks into thread pools, but performance enhancement is expected to be minimal.
278 Thread pools are built on top of Node.js [worker-threads](https://nodejs.org/api/worker_threads.html#worker_threads_worker_threads) module.
279
280 **If your task does not run into libuv thread pool** and is I/O intensive then poolifier **cluster pools** (FixedClusterPool and DynamicClusterPool) are suggested to run I/O intensive tasks, again you can still run CPU intensive tasks into cluster pools, but performance enhancement is expected to be minimal.
281 Consider that by default Node.js already has great performance for I/O tasks (asynchronous I/O).
282 Cluster pools are built on top of Node.js [cluster](https://nodejs.org/api/cluster.html) module.
283
284 If your task contains code that runs on libuv plus code that is CPU intensive or I/O intensive you either split it either combine more strategies (i.e. tune the number of libuv threads and use cluster/thread pools).
285 But in general, **always profile your application**.
286
287 ### Fixed vs Dynamic pools
288
289 To choose your pool consider that with a FixedThreadPool/FixedClusterPool or a DynamicThreadPool/DynamicClusterPool (in this case is important the min parameter passed to the constructor) your application memory footprint will increase.
290 Increasing the memory footprint, your application will be ready to accept more tasks, but during idle time your application will consume more memory.
291 One good choice from poolifier team point of view is to profile your application using fixed or dynamic worker pool, and to see your application metrics when you increase/decrease the num of workers.
292 For example you could keep the memory footprint low choosing a DynamicThreadPool/DynamicClusterPool with 5 workers, and allow to create new workers until 50/100 when needed, this is the advantage to use the DynamicThreadPool/DynamicClusterPool.
293 But in general, **always profile your application**.
294
295 ## Contribute
296
297 Choose your task here [2.6.x](https://github.com/orgs/poolifier/projects/1), propose an idea, a fix, an improvement.
298
299 See [CONTRIBUTING](CONTRIBUTING.md) guidelines.
300
301 ## Team
302
303 **Creator/Owner:**
304
305 - [**Alessandro Pio Ardizio**](https://github.com/pioardi)
306
307 **_Contributors_**
308
309 - [**Shinigami92**](https://github.com/Shinigami92)
310 - [**Jérôme Benoit**](https://github.com/jerome-benoit)
311
312 ## License
313
314 [MIT](./LICENSE)