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Graceful Shutdown Draining In Flight Work

A shutdown coordinator that stops accepting work, waits for in-flight tasks to settle, and force-cancels whatever remains after a deadline.

JavascriptResilience

Code

export async function drain(tracked, options = {}) {
  const { deadlineMs = 5000, onForceCancel } = options;
  if (!Array.isArray(tracked)) throw new TypeError("tracked must be an array");
  if (tracked.length === 0) {
    return { completed: 0, cancelled: 0, timedOut: false };
  }

  const settled = tracked.map((p) => Promise.resolve(p).then(() => "done", () => "failed"));
  let timedOut = false;
  const outcomes = await Promise.race([
    Promise.all(settled),
    new Promise((resolve) =>
      setTimeout(() => {
        timedOut = true;
        if (onForceCancel) onForceCancel();
        resolve(tracked.map(() => "cancelled"));
      }, deadlineMs),
    ),
  ]);

  const completed = outcomes.filter((o) => o === "done" || o === "failed").length;
  const cancelled = outcomes.filter((o) => o === "cancelled").length;
  return { completed, cancelled, timedOut };
}

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