Redis Distributed Lock Acquisition

import { createClient } from 'redis';

const redis = createClient({ url: 'redis://127.0.0.1:6379' });
await redis.connect();

function randomToken() {
  return crypto.randomUUID();
}

async function acquireLock(key: string, ttlMs: number) {
  const token = randomToken();
  const ok = await redis.set('lock:' + key, token, { NX: true, PX: ttlMs });
  return ok ? token : null;
}

async function releaseLock(key: string, token: string) {
  const script = `
    if redis.call("GET", KEYS[1]) == ARGV[1] then
      return redis.call("DEL", KEYS[1])
    else
      return 0
    end
  `;
  return (await redis.eval(script, {
    keys: ['lock:' + key],
    arguments: [token],
  })) === 1;
}

async function withLock<T>(
  key: string, ttlMs: number, fn: () => Promise<T>,
): Promise<T | null> {
  const token = await acquireLock(key, ttlMs);
  if (token === null) return null;

  const renew = setInterval(() => {
    redis.expire('lock:' + key, ttlMs / 1000).catch(() => {});
  }, ttlMs / 3);

  try {
    return await fn();
  } finally {
    clearInterval(renew);
    await releaseLock(key, token);
  }
}

const result = await withLock('billing:nightly', 30_000, async () => {
  console.log('nightly billing started under lock');
  return { invoices: 42 };
});
console.log('lock result:', result?.invoices ?? 'busy');