cloudflare-domain-manager/apps/api/src/services/routing/binding-lock.ts

const locks = new Map<number, Promise<void>>();

export async function withBindingLock<T>(
  bindingId: number,
  fn: () => Promise<T>,
): Promise<T> {
  const previous = locks.get(bindingId) ?? Promise.resolve();
  let release!: () => void;
  const current = new Promise<void>((resolve) => {
    release = resolve;
  });
  locks.set(
    bindingId,
    previous.then(() => current).catch(() => current),
  );
  await previous.catch(() => undefined);
  try {
    return await fn();
  } finally {
    release();
    if (locks.get(bindingId) === current) {
      locks.delete(bindingId);
    }
  }
}