Function tryAcquireSchedulerLock

src/utils/cronTasksLock.ts:111–173

(
  opts?: SchedulerLockOptions,
)

 * If two sessions race to recover a stale lock, only one create succeeds.
 */
export async function tryAcquireSchedulerLock(
  opts?: SchedulerLockOptions,
): Promise<boolean> {
  const dir = opts?.dir
  // "sessionId" in the lock file is really just a stable owner key. REPL
  // uses getSessionId(); daemon callers supply their own UUID. PID remains
  // the liveness signal regardless.
  const sessionId = opts?.lockIdentity ?? getSessionId()
  const lock: SchedulerLock = {
    sessionId,
    pid: process.pid,
    acquiredAt: Date.now(),
  }

  if (await tryCreateExclusive(lock, dir)) {
    lastBlockedBy = undefined
    registerLockCleanup(opts)
    logForDebugging(
      `[ScheduledTasks] acquired scheduler lock (PID ${process.pid})`,
    )
    return true
  }

  const existing = await readLock(dir)

  // Already ours (idempotent). After --resume the session ID is restored
  // but the process has a new PID — update the lock file so other sessions
  // see a live PID and don't steal it.
  if (existing?.sessionId === sessionId) {
    if (existing.pid !== process.pid) {
      await writeFile(getLockPath(dir), jsonStringify(lock))
      registerLockCleanup(opts)
    }
    return true
  }

  // Corrupt or unparseable — treat as stale.
  // Another live session — blocked.
  if (existing && isProcessRunning(existing.pid)) {
    if (lastBlockedBy !== existing.sessionId) {
      lastBlockedBy = existing.sessionId
      logForDebugging(
        `[ScheduledTasks] scheduler lock held by session ${existing.sessionId} (PID ${existing.pid})`,
      )
    }
    return false
  }

  // Stale — unlink and retry the exclusive create once.
  if (existing) {
    logForDebugging(
      `[ScheduledTasks] recovering stale scheduler lock from PID ${existing.pid}`,
    )
  }
  await unlink(getLockPath(dir)).catch(() => {})
  if (await tryCreateExclusive(lock, dir)) {
    lastBlockedBy = undefined
    registerLockCleanup(opts)