Aborting

How to pass an AbortSignal to a lock request to abort a pending acquisition, and when aborts take effect.

Overview

The function API and the Asyncmux class accept an AbortSignal to abort a lock wait. The decorator API does not.

// Function API
using _ = await asyncmux(this, signal);

// Asyncmux class
using _ = await mux.lock({ key: "key", signal });

When aborts take effect

• When the signal is already aborted at call time, the lock is never requested and the call rejects immediately with signal.reason.
• When aborted while waiting, the request is removed from the queue and rejects with signal.reason. Subsequent requests continue to be processed.
• Aborting after the lock has been acquired does not release it. Release it with release() or using.

import { Asyncmux } from "asyncmux";

const mux = new Asyncmux();
const controller = new AbortController();

const lockPromise = mux.lock({
  key: "resource",
  signal: controller.signal,
});

setTimeout(() => {
  controller.abort(new Error("Timed out"));
}, 1000);

const lock = await lockPromise.catch((error) => {
  // On abort, signal.reason is passed through as-is.
  console.error(error);
  return null;
});

if (lock) {
  try {
    // Run with the lock acquired.
  } finally {
    lock.release();
  }
}

Abort reason

The value passed to AbortController.abort() becomes signal.reason. When omitted, the runtime’s AbortError (DOMException) is used as the reason.

const controller = new AbortController();
controller.abort("Abort reason");

await asyncmux(target, controller.signal); // Rejects with "Abort reason".