Async Semaphore
A counting semaphore based on Java's Concurrent Semaphore.
Install
Install the module via npm:
npm install ts-async-semaphore
Quick Example
// fairness false
import { Semaphore } from 'ts-async-semaphore';
const semaphore = new Semaphore(0);
semaphore.acquire(2).then(() => {
console.log('Hello');
});
semaphore.acquire().then(() => {
console.log('World');
semaphore.release(2);
});
setTimeout(function () {
semaphore.release();
}, 2000);
// fairness true
import { Semaphore } from 'ts-async-semaphore';
const semaphore = new Semaphore(0, true);
semaphore.acquire(2).then(() => {
console.log('Hello');
});
semaphore.acquire().then(() => {
console.log('World');
});
semaphore.release(1);
setTimeout(function () {
semaphore.release(2);
}, 2000);
import { Semaphore } from 'ts-async-semaphore';
const semaphore = new Semaphore(0, true);
semaphore.tryAcquire(1, 50).then((val) => {
console.log(`Acquire ${val ? 'success' : 'fail'}`);
});
Documentation
Constructor: Semaphore([permits], [fairness])
permits: Integer Initial available permits of semaphore. Default: 0.
fairness: Boolean Fairness of semaphore. If set to true, a FIFO rules applied, else, look on each acquirers permit value.
#availablePermits()
Returns the current number of permits available in this semaphore.
Returns: number
#acquire([permits])
Acquires the given number of permits from this semaphore.
permits: number The number of permits to acquire. Default: 0.
Returns: Promise<void>
#getQueuedAcquirers()
Returns an estimate of the number of acquirers waiting to acquire.
Returns: Function[]
#getQueueLength()
Returns an estimate of the number of acquirers waiting to acquire.
Returns: number
#release([permits])
Releases the given number of permits, returning them to the semaphore.
permits: number The number of permits to release. Default: 0.
#drainPermits()
Acquires and returns all permits that are immediately available.
Returns: number
#reducePermits(permits)
Shrinks the number of available permits by the indicated reduction.
permits: number The number of permits to remove.
#tryAcquire([permits], [timeoutMs])
Acquires the given number of permits from this semaphore.
permits: number The number of permits to acquire. Default: 0.
timeoutMs: number The timeout after which the acquire will fail
Returns: Boolean Promise true if success, false false if fail
