| 1 | import EventEmitter from 'events' |
| 2 | import type { MessageValue } from '../utility-types' |
| 3 | import type { IPool } from './pool' |
| 4 | |
| 5 | /** |
| 6 | * Callback invoked if the worker raised an error. |
| 7 | */ |
| 8 | export type ErrorHandler<Worker> = (this: Worker, e: Error) => void |
| 9 | |
| 10 | /** |
| 11 | * Callback invoked when the worker has started successfully. |
| 12 | */ |
| 13 | export type OnlineHandler<Worker> = (this: Worker) => void |
| 14 | |
| 15 | /** |
| 16 | * Callback invoked when the worker exits successfully. |
| 17 | */ |
| 18 | export type ExitHandler<Worker> = (this: Worker, code: number) => void |
| 19 | |
| 20 | /** |
| 21 | * Basic interface that describes the minimum required implementation of listener events for a pool-worker. |
| 22 | */ |
| 23 | export interface IWorker { |
| 24 | on(event: 'error', handler: ErrorHandler<this>): void |
| 25 | on(event: 'online', handler: OnlineHandler<this>): void |
| 26 | on(event: 'exit', handler: ExitHandler<this>): void |
| 27 | } |
| 28 | |
| 29 | /** |
| 30 | * Options for a poolifier pool. |
| 31 | */ |
| 32 | export interface PoolOptions<Worker> { |
| 33 | /** |
| 34 | * A function that will listen for error event on each worker. |
| 35 | */ |
| 36 | errorHandler?: ErrorHandler<Worker> |
| 37 | /** |
| 38 | * A function that will listen for online event on each worker. |
| 39 | */ |
| 40 | onlineHandler?: OnlineHandler<Worker> |
| 41 | /** |
| 42 | * A function that will listen for exit event on each worker. |
| 43 | */ |
| 44 | exitHandler?: ExitHandler<Worker> |
| 45 | /** |
| 46 | * This is just to avoid non-useful warning messages. |
| 47 | * |
| 48 | * Will be used to set `maxListeners` on event emitters (workers are event emitters). |
| 49 | * |
| 50 | * @default 1000 |
| 51 | * @see [Node events emitter.setMaxListeners(n)](https://nodejs.org/api/events.html#events_emitter_setmaxlisteners_n) |
| 52 | */ |
| 53 | maxTasks?: number |
| 54 | } |
| 55 | |
| 56 | /** |
| 57 | * Internal poolifier pool emitter. |
| 58 | */ |
| 59 | class PoolEmitter extends EventEmitter {} |
| 60 | |
| 61 | /** |
| 62 | * Base class containing some shared logic for all poolifier pools. |
| 63 | * |
| 64 | * @template Worker Type of worker which manages this pool. |
| 65 | * @template Data Type of data sent to the worker. |
| 66 | * @template Response Type of response of execution. |
| 67 | */ |
| 68 | export abstract class AbstractPool< |
| 69 | Worker extends IWorker, |
| 70 | Data = unknown, |
| 71 | Response = unknown |
| 72 | > implements IPool<Data, Response> { |
| 73 | /** |
| 74 | * List of currently available workers. |
| 75 | */ |
| 76 | public readonly workers: Worker[] = [] |
| 77 | |
| 78 | /** |
| 79 | * ID for the next worker. |
| 80 | */ |
| 81 | public nextWorker: number = 0 |
| 82 | |
| 83 | /** |
| 84 | * - `key`: The `Worker` |
| 85 | * - `value`: Number of tasks that has been assigned to that worker since it started |
| 86 | */ |
| 87 | public readonly tasks: Map<Worker, number> = new Map<Worker, number>() |
| 88 | |
| 89 | /** |
| 90 | * Emitter on which events can be listened to. |
| 91 | * |
| 92 | * Events that can currently be listened to: |
| 93 | * |
| 94 | * - `'FullPool'` |
| 95 | */ |
| 96 | public readonly emitter: PoolEmitter |
| 97 | |
| 98 | /** |
| 99 | * ID of the next message. |
| 100 | */ |
| 101 | protected id: number = 0 |
| 102 | |
| 103 | /** |
| 104 | * Constructs a new poolifier pool. |
| 105 | * |
| 106 | * @param numWorkers Number of workers that this pool should manage. |
| 107 | * @param filePath Path to the worker-file. |
| 108 | * @param opts Options for the pool. Default: `{ maxTasks: 1000 }` |
| 109 | */ |
| 110 | public constructor ( |
| 111 | public readonly numWorkers: number, |
| 112 | public readonly filePath: string, |
| 113 | public readonly opts: PoolOptions<Worker> = { maxTasks: 1000 } |
| 114 | ) { |
| 115 | if (!this.isMain()) { |
| 116 | throw new Error('Cannot start a pool from a worker!') |
| 117 | } |
| 118 | // TODO christopher 2021-02-07: Improve this check e.g. with a pattern or blank check |
| 119 | if (!this.filePath) { |
| 120 | throw new Error('Please specify a file with a worker implementation') |
| 121 | } |
| 122 | |
| 123 | this.setupHook() |
| 124 | |
| 125 | for (let i = 1; i <= this.numWorkers; i++) { |
| 126 | this.internalNewWorker() |
| 127 | } |
| 128 | |
| 129 | this.emitter = new PoolEmitter() |
| 130 | } |
| 131 | |
| 132 | /** |
| 133 | * Setup hook that can be overridden by a Poolifer pool implementation |
| 134 | * to run code before workers are created in the abstract constructor. |
| 135 | */ |
| 136 | protected setupHook (): void { |
| 137 | // Can be overridden |
| 138 | } |
| 139 | |
| 140 | /** |
| 141 | * Should return whether the worker is the main worker or not. |
| 142 | */ |
| 143 | protected abstract isMain (): boolean |
| 144 | |
| 145 | public async destroy (): Promise<void> { |
| 146 | for (const worker of this.workers) { |
| 147 | await this.destroyWorker(worker) |
| 148 | } |
| 149 | } |
| 150 | |
| 151 | /** |
| 152 | * Shut down given worker. |
| 153 | * |
| 154 | * @param worker A worker within `workers`. |
| 155 | */ |
| 156 | protected abstract destroyWorker (worker: Worker): void | Promise<void> |
| 157 | |
| 158 | /** |
| 159 | * Send a message to the given worker. |
| 160 | * |
| 161 | * @param worker The worker which should receive the message. |
| 162 | * @param message The message. |
| 163 | */ |
| 164 | protected abstract sendToWorker ( |
| 165 | worker: Worker, |
| 166 | message: MessageValue<Data> |
| 167 | ): void |
| 168 | |
| 169 | /** |
| 170 | * Adds the given worker to the pool. |
| 171 | * |
| 172 | * @param worker Worker that will be added. |
| 173 | */ |
| 174 | protected addWorker (worker: Worker): void { |
| 175 | const previousWorkerIndex = this.tasks.get(worker) |
| 176 | if (previousWorkerIndex !== undefined) { |
| 177 | this.tasks.set(worker, previousWorkerIndex + 1) |
| 178 | } else { |
| 179 | throw Error('Worker could not be found in tasks map') |
| 180 | } |
| 181 | } |
| 182 | |
| 183 | /** |
| 184 | * Removes the given worker from the pool. |
| 185 | * |
| 186 | * @param worker Worker that will be removed. |
| 187 | */ |
| 188 | protected removeWorker (worker: Worker): void { |
| 189 | // Clean worker from data structure |
| 190 | const workerIndex = this.workers.indexOf(worker) |
| 191 | this.workers.splice(workerIndex, 1) |
| 192 | this.tasks.delete(worker) |
| 193 | } |
| 194 | |
| 195 | public execute (data: Data): Promise<Response> { |
| 196 | // Configure worker to handle message with the specified task |
| 197 | const worker = this.chooseWorker() |
| 198 | this.addWorker(worker) |
| 199 | const id = ++this.id |
| 200 | const res = this.internalExecute(worker, id) |
| 201 | this.sendToWorker(worker, { data: data || ({} as Data), id: id }) |
| 202 | return res |
| 203 | } |
| 204 | |
| 205 | protected abstract registerWorkerMessageListener ( |
| 206 | port: Worker, |
| 207 | listener: (message: MessageValue<Response>) => void |
| 208 | ): void |
| 209 | |
| 210 | protected abstract unregisterWorkerMessageListener ( |
| 211 | port: Worker, |
| 212 | listener: (message: MessageValue<Response>) => void |
| 213 | ): void |
| 214 | |
| 215 | protected internalExecute (worker: Worker, id: number): Promise<Response> { |
| 216 | return new Promise((resolve, reject) => { |
| 217 | const listener: (message: MessageValue<Response>) => void = message => { |
| 218 | if (message.id === id) { |
| 219 | this.unregisterWorkerMessageListener(worker, listener) |
| 220 | this.addWorker(worker) |
| 221 | if (message.error) reject(message.error) |
| 222 | else resolve(message.data as Response) |
| 223 | } |
| 224 | } |
| 225 | this.registerWorkerMessageListener(worker, listener) |
| 226 | }) |
| 227 | } |
| 228 | |
| 229 | /** |
| 230 | * Choose a worker for the next task. |
| 231 | * |
| 232 | * The default implementation uses a round robin algorithm to distribute the load. |
| 233 | * |
| 234 | * @returns Worker. |
| 235 | */ |
| 236 | protected chooseWorker (): Worker { |
| 237 | this.nextWorker = |
| 238 | this.nextWorker === this.workers.length - 1 ? 0 : this.nextWorker + 1 |
| 239 | return this.workers[this.nextWorker] |
| 240 | } |
| 241 | |
| 242 | /** |
| 243 | * Returns a newly created worker. |
| 244 | */ |
| 245 | protected abstract newWorker (): Worker |
| 246 | |
| 247 | /** |
| 248 | * Function that can be hooked up when a worker has been newly created and moved to the workers registry. |
| 249 | * |
| 250 | * Can be used to update the `maxListeners` or binding the `main-worker`<->`worker` connection if not bind by default. |
| 251 | * |
| 252 | * @param worker The newly created worker. |
| 253 | */ |
| 254 | protected abstract afterNewWorkerPushed (worker: Worker): void |
| 255 | |
| 256 | /** |
| 257 | * Creates a new worker for this pool and sets it up completely. |
| 258 | * |
| 259 | * @returns New, completely set up worker. |
| 260 | */ |
| 261 | protected internalNewWorker (): Worker { |
| 262 | const worker: Worker = this.newWorker() |
| 263 | worker.on('error', this.opts.errorHandler ?? (() => {})) |
| 264 | worker.on('online', this.opts.onlineHandler ?? (() => {})) |
| 265 | // TODO handle properly when a worker exit |
| 266 | worker.on('exit', this.opts.exitHandler ?? (() => {})) |
| 267 | this.workers.push(worker) |
| 268 | this.afterNewWorkerPushed(worker) |
| 269 | // init tasks map |
| 270 | this.tasks.set(worker, 0) |
| 271 | return worker |
| 272 | } |
| 273 | } |