gristlabs_grist-core/app/common/KeyedMutex.ts

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