bullmq

BullMQ

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BullMQ is a Redis-based distributed job and message queue for Node.js with workers, schedulers, flows, and built-in rate limiting.

Key Capabilities

BullMQ has built-ins that replace common patterns developers reach for external solutions to solve:

• Flow Producers: model parent-child job dependencies natively — no custom orchestration layer needed. A parent job only runs after all its children complete.
• Sandboxed Processors: run worker processors in isolated child processes (processor: './worker.js') — no separate process manager or worker-threads wiring needed.
• Job Schedulers: built-in repeating job scheduler with cron and interval strategies. Note: QueueScheduler (v1) was removed in v2 when stall detection moved into Worker; the legacy repeat option on queue.add() was separately deprecated in v5.16+ in favor of upsertJobScheduler(). No node-cron needed.
• Global Rate Limiting: enforce a max-jobs-per-duration limit via the limiter option on the Worker constructor ({ limiter: { max: 10, duration: 1000 } }) — no Redis Lua scripting needed.
• Built-in Metrics: track processed/failed counts and Prometheus-compatible metrics without a separate metrics library.

Best Practices

• Always close connections explicitly: Queue, Worker, and QueueEvents each hold their own Redis connection. Call .close() on all three on shutdown or you will leak connections and block process exit.
• Use QueueEvents for cross-process event listening: the Worker emits events only within its own process. To listen to completed/failed events from a different process (e.g. an API server), instantiate a QueueEvents object — not a Worker.
• Job Schedulers replace Repeatable Jobs in v5.16+: the old repeat option on queue.add() is deprecated. Use queue.upsertJobScheduler() instead to avoid duplicate scheduler entries on restart.
• Set removeOnComplete and removeOnFail: by default completed and failed jobs accumulate in Redis indefinitely. Always configure auto-removal (e.g. { count: 1000 }) to prevent unbounded memory growth.
• Do not share a single IORedis connection across multiple BullMQ instances: BullMQ uses blocking Redis commands that require dedicated connections. Pass a connection config object (not a shared IORedis instance) so each class can create its own connection.