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c97c7edb S |
1 | import EventEmitter from 'events' |
2 | import type { MessageValue } from '../utility-types' | |
3 | import type { IPool } from './pool' | |
4 | ||
5 | export type ErrorHandler<Worker> = (this: Worker, e: Error) => void | |
6 | export type OnlineHandler<Worker> = (this: Worker) => void | |
7 | export type ExitHandler<Worker> = (this: Worker, code: number) => void | |
8 | ||
9 | export interface IWorker { | |
10 | on(event: 'error', handler: ErrorHandler<this>): void | |
11 | on(event: 'online', handler: OnlineHandler<this>): void | |
12 | on(event: 'exit', handler: ExitHandler<this>): void | |
13 | } | |
14 | ||
15 | export interface PoolOptions<Worker> { | |
16 | /** | |
17 | * A function that will listen for error event on each worker. | |
18 | */ | |
19 | errorHandler?: ErrorHandler<Worker> | |
20 | /** | |
21 | * A function that will listen for online event on each worker. | |
22 | */ | |
23 | onlineHandler?: OnlineHandler<Worker> | |
24 | /** | |
25 | * A function that will listen for exit event on each worker. | |
26 | */ | |
27 | exitHandler?: ExitHandler<Worker> | |
28 | /** | |
29 | * This is just to avoid not useful warnings message, is used to set `maxListeners` on event emitters (workers are event emitters). | |
30 | * | |
31 | * @default 1000 | |
32 | */ | |
33 | maxTasks?: number | |
34 | } | |
35 | ||
36 | class PoolEmitter extends EventEmitter {} | |
37 | ||
38 | export abstract class AbstractPool< | |
39 | Worker extends IWorker, | |
d3c8a1a8 S |
40 | Data = unknown, |
41 | Response = unknown | |
c97c7edb S |
42 | > implements IPool<Data, Response> { |
43 | public readonly workers: Worker[] = [] | |
44 | public nextWorker: number = 0 | |
45 | ||
46 | /** | |
47 | * `workerId` as key and an integer value | |
48 | */ | |
49 | public readonly tasks: Map<Worker, number> = new Map<Worker, number>() | |
50 | ||
51 | public readonly emitter: PoolEmitter | |
52 | ||
53 | protected id: number = 0 | |
54 | ||
55 | public constructor ( | |
56 | public readonly numWorkers: number, | |
57 | public readonly filePath: string, | |
58 | public readonly opts: PoolOptions<Worker> = { maxTasks: 1000 } | |
59 | ) { | |
60 | if (!this.isMain()) { | |
61 | throw new Error('Cannot start a pool from a worker!') | |
62 | } | |
63 | // TODO christopher 2021-02-07: Improve this check e.g. with a pattern or blank check | |
64 | if (!this.filePath) { | |
65 | throw new Error('Please specify a file with a worker implementation') | |
66 | } | |
67 | ||
68 | this.setupHook() | |
69 | ||
70 | for (let i = 1; i <= this.numWorkers; i++) { | |
71 | this.internalNewWorker() | |
72 | } | |
73 | ||
74 | this.emitter = new PoolEmitter() | |
75 | } | |
76 | ||
77 | protected setupHook (): void { | |
78 | // Can be overridden | |
79 | } | |
80 | ||
81 | protected abstract isMain (): boolean | |
82 | ||
83 | public async destroy (): Promise<void> { | |
84 | for (const worker of this.workers) { | |
85 | await this.destroyWorker(worker) | |
86 | } | |
87 | } | |
88 | ||
89 | protected abstract destroyWorker (worker: Worker): void | Promise<void> | |
90 | ||
91 | protected abstract sendToWorker ( | |
92 | worker: Worker, | |
93 | message: MessageValue<Data> | |
94 | ): void | |
95 | ||
96 | protected addWorker (worker: Worker): void { | |
97 | const previousWorkerIndex = this.tasks.get(worker) | |
98 | if (previousWorkerIndex !== undefined) { | |
99 | this.tasks.set(worker, previousWorkerIndex + 1) | |
100 | } else { | |
101 | throw Error('Worker could not be found in tasks map') | |
102 | } | |
103 | } | |
104 | ||
105 | /** | |
106 | * Execute the task specified into the constructor with the data parameter. | |
107 | * | |
108 | * @param data The input for the task specified. | |
109 | * @returns Promise that is resolved when the task is done. | |
110 | */ | |
111 | public execute (data: Data): Promise<Response> { | |
112 | // configure worker to handle message with the specified task | |
113 | const worker = this.chooseWorker() | |
114 | this.addWorker(worker) | |
115 | const id = ++this.id | |
116 | const res = this.internalExecute(worker, id) | |
117 | this.sendToWorker(worker, { data: data || ({} as Data), id: id }) | |
118 | return res | |
119 | } | |
120 | ||
121 | protected abstract registerWorkerMessageListener ( | |
122 | port: Worker, | |
123 | listener: (message: MessageValue<Response>) => void | |
124 | ): void | |
125 | ||
126 | protected abstract unregisterWorkerMessageListener ( | |
127 | port: Worker, | |
128 | listener: (message: MessageValue<Response>) => void | |
129 | ): void | |
130 | ||
131 | protected internalExecute (worker: Worker, id: number): Promise<Response> { | |
132 | return new Promise((resolve, reject) => { | |
133 | const listener: (message: MessageValue<Response>) => void = message => { | |
134 | if (message.id === id) { | |
135 | this.unregisterWorkerMessageListener(worker, listener) | |
136 | this.addWorker(worker) | |
137 | if (message.error) reject(message.error) | |
138 | else resolve(message.data as Response) | |
139 | } | |
140 | } | |
141 | this.registerWorkerMessageListener(worker, listener) | |
142 | }) | |
143 | } | |
144 | ||
145 | protected chooseWorker (): Worker { | |
146 | if (this.workers.length - 1 === this.nextWorker) { | |
147 | this.nextWorker = 0 | |
148 | return this.workers[this.nextWorker] | |
149 | } else { | |
150 | this.nextWorker++ | |
151 | return this.workers[this.nextWorker] | |
152 | } | |
153 | } | |
154 | ||
155 | protected abstract newWorker (): Worker | |
156 | ||
157 | protected abstract afterNewWorkerPushed (worker: Worker): void | |
158 | ||
159 | protected internalNewWorker (): Worker { | |
160 | const worker: Worker = this.newWorker() | |
161 | worker.on('error', this.opts.errorHandler ?? (() => {})) | |
162 | worker.on('online', this.opts.onlineHandler ?? (() => {})) | |
163 | // TODO handle properly when a worker exit | |
164 | worker.on('exit', this.opts.exitHandler ?? (() => {})) | |
165 | this.workers.push(worker) | |
166 | this.afterNewWorkerPushed(worker) | |
167 | // init tasks map | |
168 | this.tasks.set(worker, 0) | |
169 | return worker | |
170 | } | |
171 | } |