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47 lines
1.3 KiB
47 lines
1.3 KiB
import { Mutex, MutexInterface } from 'async-mutex';
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/**
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* A per-key mutex. It has the same interface as Mutex, but with an extra key supplied.
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* Maintains an independent mutex for each key on need.
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*/
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export class KeyedMutex {
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private _mutexes = new Map<string, Mutex>();
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public async acquire(key: string): Promise<MutexInterface.Releaser> {
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// Create a new mutex if we need one.
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if (!this._mutexes.has(key)) {
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this._mutexes.set(key, new Mutex());
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}
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const mutex = this._mutexes.get(key)!;
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const unlock = await mutex.acquire();
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return () => {
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unlock();
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// After unlocking, clean-up the mutex if it is no longer needed.
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// unlock() leaves the mutex locked if anyone has been waiting for it.
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if (!mutex.isLocked()) {
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this._mutexes.delete(key);
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}
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};
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}
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public async runExclusive<T>(key: string, callback: MutexInterface.Worker<T>): Promise<T> {
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const unlock = await this.acquire(key);
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try {
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return await callback();
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} finally {
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unlock();
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}
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}
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public isLocked(key: string): boolean {
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const mutex = this._mutexes.get(key);
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if (!mutex) { return false; }
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return mutex.isLocked();
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}
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// Check how many mutexes are in use.
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public get size(): number {
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return this._mutexes.size;
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}
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}
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