davegurnell/semaphore-promise

semaphore-promise

Promise based, TypeScript compatible semaphore library.

const Semaphore = require( 'semaphore-promise' );

const semaphore = new Semaphore( 1 );
semaphore.acquire().then( ( release ) => {
    // Do something exclusive
    release();
} );

This library can be used in TypeScript files as well.

import Semaphore from 'semaphore-promise';

API

Semaphore( count : number, opts? : opts )

Creates a new semaphore object with count semaphores.

opts can contain …

• a name for the semaphore which is used by the logger.
• a logger like pino to log debug messages. If no logger is provided, nothing is logged.

acquire() : Promise<() => void>

Resolves as soon as a semaphore could be acquired. Waiting callers are treated in FIFO order.

Returns a release function which is needed to release() the semaphore again.

tryAcquire() : () => void

• If a semaphore is available, acquire it and return a release function.
• Else, throw an Error.

Changelog

• v1.4.0 (2022-05-06)
  • Add logging capabilities to simplify debugging issues like deadlocks.
  • Add names to semaphore, also for debugging.
• v1.3.0 (2022-02-10)
  • Add default export so import Semaphore from 'semaphore-promise' can be used (without curly braces)
  • Default to 1 semaphore in the constructor
  • Docs: Add note on FIFO order
• v1.2.0 (2019-08-07)
  • Add tryAcquire()