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4
5<h2 align="center">Node Thread Pool and Cluster Pool :arrow_double_up: :on:</h2>
6
7<p align="center">
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28</p>
29
30## Why Poolifier?
31
32Poolifier is used to perform CPU and/or I/O intensive tasks on Node.js servers, it implements worker pools using [worker_threads](https://nodejs.org/api/worker_threads.html) and [cluster](https://nodejs.org/api/cluster.html) Node.js modules.
33With poolifier you can improve your **performance** and resolve problems related to the event loop.
34Moreover you can execute your tasks using an API designed to improve the **developer experience**.
35Please consult our [general guidelines](#general-guidance).
36
37- Easy to use :white_check_mark:
38- Performance [benchmarks](./benchmarks/README.md) :white_check_mark:
39- Static and dynamic pool size :white_check_mark:
40- Easy switch from a pool type to another :white_check_mark:
41- No runtime dependencies :white_check_mark:
42- Proper async integration with node [async_hooks](https://nodejs.org/api/async_hooks.html) :white_check_mark:
43- Support CommonJS, ESM, and TypeScript :white_check_mark:
44- Support for [worker_threads](https://nodejs.org/api/worker_threads.html) and [cluster](https://nodejs.org/api/cluster.html) Node.js 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- Error handling out of the box :white_check_mark:
49- Widely tested :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
83Poolifier contains two [worker_threads](https://nodejs.org/api/worker_threads.html#class-worker)/[cluster](https://nodejs.org/api/cluster.html#cluster_class_worker) worker pool implementations, you don't have to deal with [worker_threads](https://nodejs.org/api/worker_threads.html)/[cluster](https://nodejs.org/api/cluster.html) complexity.
84The first implementation is a static worker pool, with a defined number of workers that are started at creation time and will be reused.
85The 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.
86You have to implement your worker by extending the _ThreadWorker_ or _ClusterWorker_ class.
87
88## Installation
89
90```shell
91npm install poolifier --save
92```
93
94## Usage
95
96You can implement a [worker_threads](https://nodejs.org/api/worker_threads.html#class-worker) worker in a simple way by extending the class _ThreadWorker_:
97
98```js
99'use strict'
100const { ThreadWorker } = require('poolifier')
101
102function 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
108module.exports = new ThreadWorker(yourFunction, {
109 maxInactiveTime: 60000
110})
111```
112
113Instantiate your pool based on your needs :
114
115```js
116'use strict'
117const { DynamicThreadPool, FixedThreadPool, PoolEvents, availableParallelism } = require('poolifier')
118
119// a fixed worker_threads pool
120const pool = new FixedThreadPool(availableParallelism(), './yourWorker.js', {
121 errorHandler: e => console.error(e),
122 onlineHandler: () => console.info('worker is online')
123})
124
125pool.emitter.on(PoolEvents.ready, () => console.info('Pool is ready'))
126pool.emitter.on(PoolEvents.busy, () => console.info('Pool is busy'))
127
128// or a dynamic worker_threads pool
129const pool = new DynamicThreadPool(Math.floor(availableParallelism() / 2), availableParallelism(), './yourWorker.js', {
130 errorHandler: e => console.error(e),
131 onlineHandler: () => console.info('worker is online')
132})
133
134pool.emitter.on(PoolEvents.full, () => console.info('Pool is full'))
135pool.emitter.on(PoolEvents.ready, () => console.info('Pool is ready'))
136pool.emitter.on(PoolEvents.busy, () => console.info('Pool is busy'))
137
138// the execute method signature is the same for both implementations,
139// so you can easy switch from one to another
140pool
141 .execute({})
142 .then(res => {
143 console.info(res)
144 })
145 .catch(err => {
146 console.error(err)
147 })
148```
149
150You can do the same with the classes _ClusterWorker_, _FixedClusterPool_ and _DynamicClusterPool_.
151
152**See [examples](./examples/) folder for more details (in particular if you want to use a pool with [multiple worker functions](./examples/multiFunctionExample.js))**.
153
154Remember that workers can only send and receive structured-cloneable data.
155
156## Node versions
157
158Node versions >= 16.14.x are supported.
159
160## [API](https://poolifier.github.io/poolifier/)
161
162### `pool = new FixedThreadPool/FixedClusterPool(numberOfThreads/numberOfWorkers, filePath, opts)`
163
164`numberOfThreads/numberOfWorkers` (mandatory) Number of workers for this pool
165`filePath` (mandatory) Path to a file with a worker implementation
166`opts` (optional) An object with the pool options properties described below
167
168### `pool = new DynamicThreadPool/DynamicClusterPool(min, max, filePath, opts)`
169
170`min` (mandatory) Same as _FixedThreadPool_/_FixedClusterPool_ numberOfThreads/numberOfWorkers, this number of workers will be always active
171`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).
172`filePath` (mandatory) Path to a file with a worker implementation
173`opts` (optional) An object with the pool options properties described below
174
175### `pool.execute(data, name)`
176
177`data` (optional) An object that you want to pass to your worker implementation
178`name` (optional) A string with the task function name that you want to execute on the worker. Default: `'default'`
179
180This method is available on both pool implementations and returns a promise with the task function execution response.
181
182### `pool.destroy()`
183
184This method is available on both pool implementations and will call the terminate method on each worker.
185
186### `PoolOptions`
187
188An object with these properties:
189
190- `messageHandler` (optional) - A function that will listen for message event on each worker
191- `errorHandler` (optional) - A function that will listen for error event on each worker
192- `onlineHandler` (optional) - A function that will listen for online event on each worker
193- `exitHandler` (optional) - A function that will listen for exit event on each worker
194- `workerChoiceStrategy` (optional) - The worker choice strategy to use in this pool:
195
196 - `WorkerChoiceStrategies.ROUND_ROBIN`: Submit tasks to worker in a round robin fashion
197 - `WorkerChoiceStrategies.LEAST_USED`: Submit tasks to the worker with the minimum number of executed, executing and queued tasks
198 - `WorkerChoiceStrategies.LEAST_BUSY`: Submit tasks to the worker with the minimum tasks total execution and wait time
199 - `WorkerChoiceStrategies.LEAST_ELU`: Submit tasks to the worker with the minimum event loop utilization (ELU) (experimental)
200 - `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
201 - `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)
202 - `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
203
204 `WorkerChoiceStrategies.WEIGHTED_ROUND_ROBIN`, `WorkerChoiceStrategies.INTERLEAVED_WEIGHTED_ROUND_ROBIN` and `WorkerChoiceStrategies.FAIR_SHARE` strategies are targeted to heavy and long tasks.
205 Default: `WorkerChoiceStrategies.ROUND_ROBIN`
206
207- `workerChoiceStrategyOptions` (optional) - The worker choice strategy options object to use in this pool.
208 Properties:
209
210 - `measurement` (optional) - The measurement to use in worker choice strategies: `runTime`, `waitTime` or `elu`.
211 - `runTime` (optional) - Use the tasks [median](./src/pools/selection-strategies/README.md#median) runtime instead of the tasks average runtime in worker choice strategies.
212 - `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.
213 - `elu` (optional) - Use the tasks [median](./src/pools/selection-strategies/README.md#median) ELU instead of the tasks average ELU in worker choice strategies.
214 - `weights` (optional) - The worker weights to use in weighted round robin worker choice strategies: `{ 0: 200, 1: 300, ..., n: 100 }`.
215
216 Default: `{ runTime: { median: false }, waitTime: { median: false }, elu: { median: false } }`
217
218- `restartWorkerOnError` (optional) - Restart worker on uncaught error in this pool.
219 Default: `true`
220- `enableEvents` (optional) - Events emission enablement in this pool.
221 Default: `true`
222- `enableTasksQueue` (optional) - Tasks queue per worker enablement in this pool.
223 Default: `false`
224
225- `tasksQueueOptions` (optional) - The worker tasks queue options object to use in this pool.
226 Properties:
227
228 - `concurrency` (optional) - The maximum number of tasks that can be executed concurrently on a worker.
229
230 Default: `{ concurrency: 1 }`
231
232#### `ThreadPoolOptions extends PoolOptions`
233
234- `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.
235
236#### `ClusterPoolOptions extends PoolOptions`
237
238- `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.
239
240- `settings` (optional) - An object with the cluster settings. See [cluster](https://nodejs.org/api/cluster.html#cluster_cluster_settings) for more details.
241
242### `class YourWorker extends ThreadWorker/ClusterWorker`
243
244`taskFunctions` (mandatory) The task function or task functions object `{ name_1: fn_1, ..., name_n: fn_n }` that you want to execute on the worker
245`opts` (optional) An object with these properties:
246
247- `maxInactiveTime` (optional) - Maximum waiting time in milliseconds for tasks on newly created workers. After this time newly created workers will die.
248 The last active time of your worker will be updated when it terminates a task.
249 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 before completion and removed. The worker is killed if is not part of the minimum size of the pool.
250 If `killBehavior` is set to `KillBehaviors.SOFT` your tasks have no timeout and your workers will not be terminated until your task is completed.
251 Default: `60000`
252
253- `killBehavior` (optional) - Dictates if your worker will be deleted in case a task is active on it.
254 **KillBehaviors.SOFT**: If `currentTime - lastActiveTime` is greater than `maxInactiveTime` but a task is still executing or queued, then the worker **won't** be deleted.
255 **KillBehaviors.HARD**: If `currentTime - lastActiveTime` is greater than `maxInactiveTime` but a task is still executing or queued, then the worker will be deleted.
256 This option only apply to the newly created workers.
257 Default: `KillBehaviors.SOFT`
258
259#### `YourWorker.hasTaskFunction(name)`
260
261`name` (mandatory) The task function name
262
263This method is available on both worker implementations and returns a boolean.
264
265#### `YourWorker.addTaskFunction(name, fn)`
266
267`name` (mandatory) The task function name
268`fn` (mandatory) The task function
269
270This method is available on both worker implementations and returns a boolean.
271
272#### `YourWorker.removeTaskFunction(name)`
273
274`name` (mandatory) The task function name
275
276This method is available on both worker implementations and returns a boolean.
277
278#### `YourWorker.listTaskFunctions()`
279
280This method is available on both worker implementations and returns an array of the task function names.
281
282#### `YourWorker.setDefaultTaskFunction(name)`
283
284`name` (mandatory) The task function name
285
286This method is available on both worker implementations and returns a boolean.
287
288## General guidance
289
290Performance is one of the main target of these worker pool implementations, poolifier team wants to have a strong focus on this.
291Poolifier already has a [benchmarks](./benchmarks/) folder where you can find some comparisons.
292
293### Internal Node.js thread pool
294
295Before 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.
296Please 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).
297
298**If your task runs on libuv thread pool**, you can try to:
299
300- Tune the libuv thread pool size setting the [UV_THREADPOOL_SIZE](https://nodejs.org/api/cli.html#cli_uv_threadpool_size_size).
301
302and/or
303
304- Use poolifier cluster pools that are spawning child processes, they 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**.
305
306### Cluster vs Threads worker pools
307
308**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.
309Thread pools are built on top of Node.js [worker_threads](https://nodejs.org/api/worker_threads.html) module.
310
311**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.
312Consider that by default Node.js already has great performance for I/O tasks (asynchronous I/O).
313Cluster pools are built on top of Node.js [cluster](https://nodejs.org/api/cluster.html) module.
314
315If 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).
316But in general, **always profile your application**.
317
318### Fixed vs Dynamic pools
319
320To choose your pool consider first that with a _FixedThreadPool_/_FixedClusterPool_ or a _DynamicThreadPool_/_DynamicClusterPool_ your application memory footprint will increase.
321By doing so, your application will be ready to execute in parallel more tasks, but during idle time your application will consume more memory.
322One good choice from poolifier team point of view is to profile your application using a static or dynamic worker pool, and analyze your application metrics when you increase/decrease the number of workers.
323For example you could keep the memory footprint low by choosing a _DynamicThreadPool_/_DynamicClusterPool_ with a minimum of 5 workers, and allowing it to create new workers until a maximum of 50 workers if needed. This is the advantage of using a _DynamicThreadPool_/_DynamicClusterPool_.
324But in general, **always profile your application**.
325
326## Contribute
327
328Choose your task here [2.6.x](https://github.com/orgs/poolifier/projects/1), propose an idea, a fix, an improvement.
329
330See [CONTRIBUTING](CONTRIBUTING.md) guidelines.
331
332## Team
333
334**Creator/Owner:**
335
336- [**Alessandro Pio Ardizio**](https://github.com/pioardi)
337
338**_Contributors_**
339
340- [**Shinigami92**](https://github.com/Shinigami92)
341- [**Jérôme Benoit**](https://github.com/jerome-benoit)
342
343## License
344
345[MIT](./LICENSE)