@lucid-softworks/semaphore

A fair, promise-based counting semaphore for limiting concurrent work. Waiting callers acquire permits in FIFO order, and release functions are idempotent.

import { Semaphore } from "@lucid-softworks/semaphore";

const semaphore = new Semaphore(3);

const response = await semaphore.run(() => fetch("/api/report"));

capacity must be a positive integer. Use acquire() when a permit needs to span custom setup and cleanup:

const release = await semaphore.acquire();

try {
  await useSharedResource();
} finally {
  release();
}

The available and pending getters expose the current number of free permits and queued acquisitions.