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a35560ba S |
1 | import type { IWorker } from './abstract-pool' |
2 | import type { IPoolInternal } from './pool-internal' | |
7c0ba920 | 3 | import { PoolType } from './pool-internal' |
a35560ba S |
4 | |
5 | /** | |
6 | * Enumeration of worker choice strategies. | |
7 | */ | |
8 | export const WorkerChoiceStrategies = Object.freeze({ | |
9 | /** | |
10 | * Round robin worker selection strategy. | |
11 | */ | |
12 | ROUND_ROBIN: 'ROUND_ROBIN', | |
13 | /** | |
14 | * Less recently used worker selection strategy. | |
15 | */ | |
16 | LESS_RECENTLY_USED: 'LESS_RECENTLY_USED' | |
17 | } as const) | |
18 | ||
19 | /** | |
20 | * Worker choice strategy. | |
21 | */ | |
22 | export type WorkerChoiceStrategy = keyof typeof WorkerChoiceStrategies | |
23 | ||
24 | /** | |
25 | * Worker choice strategy interface. | |
26 | * | |
27 | * @template Worker Type of worker which manages the strategy. | |
28 | */ | |
29 | interface IWorkerChoiceStrategy<Worker extends IWorker> { | |
30 | /** | |
31 | * Choose a worker in the pool. | |
32 | */ | |
33 | choose(): Worker | |
34 | } | |
35 | ||
36 | /** | |
37 | * Selects the next worker in a round robin fashion. | |
38 | * | |
39 | * @template Worker Type of worker which manages the strategy. | |
40 | * @template Data Type of data sent to the worker. This can only be serializable data. | |
41 | * @template Response Type of response of execution. This can only be serializable data. | |
42 | */ | |
43 | class RoundRobinWorkerChoiceStrategy<Worker extends IWorker, Data, Response> | |
44 | implements IWorkerChoiceStrategy<Worker> { | |
45 | /** | |
46 | * Index for the next worker. | |
47 | */ | |
48 | private nextWorkerIndex: number = 0 | |
49 | ||
50 | /** | |
51 | * Constructs a worker choice strategy that selects in a round robin fashion. | |
52 | * | |
53 | * @param pool The pool instance. | |
54 | */ | |
55 | public constructor ( | |
56 | private readonly pool: IPoolInternal<Worker, Data, Response> | |
57 | ) {} | |
58 | ||
59 | /** @inheritdoc */ | |
60 | public choose (): Worker { | |
61 | const chosenWorker = this.pool.workers[this.nextWorkerIndex] | |
62 | this.nextWorkerIndex = | |
63 | this.pool.workers.length - 1 === this.nextWorkerIndex | |
64 | ? 0 | |
65 | : this.nextWorkerIndex + 1 | |
66 | return chosenWorker | |
67 | } | |
68 | } | |
69 | ||
70 | /** | |
71 | * Selects the less recently used worker. | |
72 | * | |
73 | * @template Worker Type of worker which manages the strategy. | |
74 | * @template Data Type of data sent to the worker. This can only be serializable data. | |
75 | * @template Response Type of response of execution. This can only be serializable data. | |
76 | */ | |
77 | class LessRecentlyUsedWorkerChoiceStrategy< | |
78 | Worker extends IWorker, | |
79 | Data, | |
80 | Response | |
81 | > implements IWorkerChoiceStrategy<Worker> { | |
82 | /** | |
83 | * Constructs a worker choice strategy that selects based on less recently used. | |
84 | * | |
85 | * @param pool The pool instance. | |
86 | */ | |
87 | public constructor ( | |
88 | private readonly pool: IPoolInternal<Worker, Data, Response> | |
89 | ) {} | |
90 | ||
91 | /** @inheritdoc */ | |
92 | public choose (): Worker { | |
7c0ba920 | 93 | const isPoolDynamic = this.pool.type === PoolType.DYNAMIC |
a35560ba S |
94 | let minNumberOfTasks = Infinity |
95 | // A worker is always found because it picks the one with fewer tasks | |
96 | let lessRecentlyUsedWorker!: Worker | |
97 | for (const [worker, numberOfTasks] of this.pool.tasks) { | |
ff5e76e1 | 98 | if (!isPoolDynamic && numberOfTasks === 0) { |
a35560ba S |
99 | return worker |
100 | } else if (numberOfTasks < minNumberOfTasks) { | |
a35560ba | 101 | lessRecentlyUsedWorker = worker |
7c0ba920 | 102 | minNumberOfTasks = numberOfTasks |
a35560ba S |
103 | } |
104 | } | |
105 | return lessRecentlyUsedWorker | |
106 | } | |
107 | } | |
108 | ||
a35560ba S |
109 | /** |
110 | * Dynamically choose a worker. | |
111 | * | |
112 | * @template Worker Type of worker which manages the strategy. | |
113 | * @template Data Type of data sent to the worker. This can only be serializable data. | |
114 | * @template Response Type of response of execution. This can only be serializable data. | |
115 | */ | |
116 | class DynamicPoolWorkerChoiceStrategy<Worker extends IWorker, Data, Response> | |
117 | implements IWorkerChoiceStrategy<Worker> { | |
118 | private workerChoiceStrategy: IWorkerChoiceStrategy<Worker> | |
119 | ||
120 | /** | |
121 | * Constructs a worker choice strategy for dynamical pools. | |
122 | * | |
123 | * @param pool The pool instance. | |
4a6952ff | 124 | * @param createDynamicallyWorkerCallback The worker creation callback for dynamic pool. |
7c0ba920 | 125 | * @param workerChoiceStrategy The worker choice strategy when the pull is busy. |
a35560ba S |
126 | */ |
127 | public constructor ( | |
128 | private readonly pool: IPoolInternal<Worker, Data, Response>, | |
4a6952ff | 129 | private createDynamicallyWorkerCallback: () => Worker, |
a35560ba S |
130 | workerChoiceStrategy: WorkerChoiceStrategy = WorkerChoiceStrategies.ROUND_ROBIN |
131 | ) { | |
ff5e76e1 | 132 | this.workerChoiceStrategy = SelectionStrategiesUtils.getWorkerChoiceStrategy( |
a35560ba S |
133 | this.pool, |
134 | workerChoiceStrategy | |
135 | ) | |
136 | } | |
137 | ||
a35560ba S |
138 | /** @inheritdoc */ |
139 | public choose (): Worker { | |
7c0ba920 JB |
140 | const freeTaskMapEntry = this.pool.findFreeTasksMapEntry() |
141 | if (freeTaskMapEntry) { | |
142 | return freeTaskMapEntry[0] | |
a35560ba S |
143 | } |
144 | ||
7c0ba920 | 145 | if (this.pool.busy) { |
a35560ba S |
146 | return this.workerChoiceStrategy.choose() |
147 | } | |
148 | ||
149 | // All workers are busy, create a new worker | |
4a6952ff | 150 | return this.createDynamicallyWorkerCallback() |
a35560ba S |
151 | } |
152 | } | |
153 | ||
154 | /** | |
155 | * The worker choice strategy context. | |
156 | * | |
157 | * @template Worker Type of worker. | |
158 | * @template Data Type of data sent to the worker. This can only be serializable data. | |
159 | * @template Response Type of response of execution. This can only be serializable data. | |
160 | */ | |
161 | export class WorkerChoiceStrategyContext< | |
162 | Worker extends IWorker, | |
163 | Data, | |
164 | Response | |
165 | > { | |
166 | // Will be set by setter in constructor | |
167 | private workerChoiceStrategy!: IWorkerChoiceStrategy<Worker> | |
168 | ||
169 | /** | |
170 | * Worker choice strategy context constructor. | |
171 | * | |
172 | * @param pool The pool instance. | |
4a6952ff | 173 | * @param createDynamicallyWorkerCallback The worker creation callback for dynamic pool. |
a35560ba S |
174 | * @param workerChoiceStrategy The worker choice strategy. |
175 | */ | |
176 | public constructor ( | |
177 | private readonly pool: IPoolInternal<Worker, Data, Response>, | |
4a6952ff | 178 | private createDynamicallyWorkerCallback: () => Worker, |
a35560ba S |
179 | workerChoiceStrategy: WorkerChoiceStrategy = WorkerChoiceStrategies.ROUND_ROBIN |
180 | ) { | |
181 | this.setWorkerChoiceStrategy(workerChoiceStrategy) | |
182 | } | |
183 | ||
184 | /** | |
185 | * Get the worker choice strategy instance specific to the pool type. | |
186 | * | |
187 | * @param workerChoiceStrategy The worker choice strategy. | |
188 | * @returns The worker choice strategy instance for the pool type. | |
189 | */ | |
190 | private getPoolWorkerChoiceStrategy ( | |
191 | workerChoiceStrategy: WorkerChoiceStrategy = WorkerChoiceStrategies.ROUND_ROBIN | |
192 | ): IWorkerChoiceStrategy<Worker> { | |
7c0ba920 | 193 | if (this.pool.type === PoolType.DYNAMIC) { |
a35560ba S |
194 | return new DynamicPoolWorkerChoiceStrategy( |
195 | this.pool, | |
4a6952ff | 196 | this.createDynamicallyWorkerCallback, |
a35560ba S |
197 | workerChoiceStrategy |
198 | ) | |
199 | } | |
ff5e76e1 JB |
200 | return SelectionStrategiesUtils.getWorkerChoiceStrategy( |
201 | this.pool, | |
202 | workerChoiceStrategy | |
203 | ) | |
a35560ba S |
204 | } |
205 | ||
206 | /** | |
207 | * Set the worker choice strategy to use in the context. | |
208 | * | |
209 | * @param workerChoiceStrategy The worker choice strategy to set. | |
210 | */ | |
211 | public setWorkerChoiceStrategy ( | |
212 | workerChoiceStrategy: WorkerChoiceStrategy | |
213 | ): void { | |
214 | this.workerChoiceStrategy = this.getPoolWorkerChoiceStrategy( | |
215 | workerChoiceStrategy | |
216 | ) | |
217 | } | |
218 | ||
219 | /** | |
220 | * Choose a worker with the underlying selection strategy. | |
221 | * | |
222 | * @returns The chosen one. | |
223 | */ | |
224 | public execute (): Worker { | |
225 | return this.workerChoiceStrategy.choose() | |
226 | } | |
227 | } | |
ff5e76e1 JB |
228 | |
229 | /** | |
7c0ba920 | 230 | * Worker selection strategies helpers class. |
ff5e76e1 JB |
231 | */ |
232 | class SelectionStrategiesUtils { | |
ff5e76e1 JB |
233 | /** |
234 | * Get the worker choice strategy instance. | |
235 | * | |
236 | * @param pool The pool instance. | |
237 | * @param workerChoiceStrategy The worker choice strategy. | |
238 | * @returns The worker choice strategy instance. | |
239 | */ | |
240 | public static getWorkerChoiceStrategy< | |
241 | Worker extends IWorker, | |
242 | Data, | |
243 | Response | |
244 | > ( | |
245 | pool: IPoolInternal<Worker, Data, Response>, | |
246 | workerChoiceStrategy: WorkerChoiceStrategy = WorkerChoiceStrategies.ROUND_ROBIN | |
247 | ): IWorkerChoiceStrategy<Worker> { | |
248 | switch (workerChoiceStrategy) { | |
249 | case WorkerChoiceStrategies.ROUND_ROBIN: | |
250 | return new RoundRobinWorkerChoiceStrategy(pool) | |
251 | case WorkerChoiceStrategies.LESS_RECENTLY_USED: | |
252 | return new LessRecentlyUsedWorkerChoiceStrategy(pool) | |
253 | default: | |
254 | throw new Error( | |
255 | `Worker choice strategy '${workerChoiceStrategy}' not found` | |
256 | ) | |
257 | } | |
258 | } | |
259 | } |