{ "id": "nodejs", "title": "Redis job queue with node-redis", "url": "https://redis.io/docs/latest/develop/use-cases/job-queue/nodejs/", "summary": "Implement a Redis job queue in Node.js with node-redis", "tags": [ "docs", "develop", "stack", "oss", "rs", "rc" ], "last_updated": "2026-05-14T08:58:05-05:00", "children": [], "page_type": "content", "content_hash": "8b744a981dee524c320f8c202e41918629e61b91343e6544d8e83157c2c86794", "sections": [ { "id": "overview", "title": "Overview", "role": "overview", "text": "This guide shows you how to implement a Redis-backed job queue in Node.js with [`node-redis`](https://redis.io/docs/latest/develop/clients/nodejs). It includes a small local web server built with Node's standard `http` module so you can enqueue jobs, watch a pool of workers drain them, and see the reclaimer recover jobs from a simulated worker crash." }, { "id": "overview", "title": "Overview", "role": "overview", "text": "A job queue lets your application offload background work — sending email, processing payments, image transcoding, ML inference, webhooks — from the request path. Producers enqueue jobs in milliseconds and return to the user; workers pull from the queue and process them on their own schedule.\n\nThat gives you:\n\n* Low-latency user-facing requests, even when downstream work is slow or bursty\n* Horizontal scale across many worker processes that share one Redis instance\n* At-least-once delivery so a worker crash doesn't lose work\n* Visibility-timeout reclaim that returns stuck jobs to the queue automatically\n* Job metadata, retry counts, and completion results in Redis hashes with TTL\n\nIn this example, each job is identified by a random hex ID and its payload, status, and result live in a Redis hash under `queue:jobs:job:{id}`. Pending IDs sit in a list, claimed IDs move atomically to a *processing* list, and completed or failed IDs land in short history lists." }, { "id": "how-it-works", "title": "How it works", "role": "content", "text": "The flow looks like this:\n\n1. The application calls `queue.enqueue(payload)`\n2. The helper writes the job metadata hash and `LPUSH`es the job ID onto the pending list\n3. A worker calls `queue.claim(timeoutMs)`\n4. The helper runs `BLMOVE` (the successor to `BRPOPLPUSH`) to atomically move the next pending ID into the processing list and writes a per-claim `claim_token` plus `claimed_at_ms` on the hash\n5. The worker runs the job and calls `queue.complete(job, result)` or `queue.fail(job, error)`\n6. `complete` removes the job from the processing list, writes the result, and `LPUSH`es the ID onto the completed history (with `LTRIM` and an `EXPIRE` on the hash for cleanup)\n7. `fail` either retries the job (back to pending) or moves it to the failed list once retries are exhausted\n\nIf a worker dies before completing a job, the job sits in the processing list with a `claimed_at_ms` older than the visibility timeout. A periodic call to `queue.reclaimStuck()` finds those jobs and moves them back to pending so another worker can pick them up.\n\nEvery state change holds the token: a worker that has been reclaimed cannot later complete or fail a job another worker has already claimed." }, { "id": "the-job-queue-helper", "title": "The job queue helper", "role": "content", "text": "The `RedisJobQueue` class wraps the queue operations\n([source](https://github.com/redis/docs/blob/main/content/develop/use-cases/job-queue/nodejs/job_queue.js)):\n\n[code example]" }, { "id": "data-model", "title": "Data model", "role": "content", "text": "Each job's state lives in a Redis hash plus a position in one of four lists:\n\n[code example]\n\nA job's hash carries:\n\n[code example]\n\nThe implementation uses:\n\n* [`LPUSH`](https://redis.io/docs/latest/commands/lpush) to add new job IDs to the pending list\n* [`BLMOVE`](https://redis.io/docs/latest/commands/blmove) to atomically claim a job into the processing list (the modern replacement for the deprecated [`BRPOPLPUSH`](https://redis.io/docs/latest/commands/brpoplpush))\n* [`LREM`](https://redis.io/docs/latest/commands/lrem) to remove a claimed job from the processing list on complete or fail\n* [`LTRIM`](https://redis.io/docs/latest/commands/ltrim) to cap the completed and failed history lists\n* [`HSET`](https://redis.io/docs/latest/commands/hset) / [`HGETALL`](https://redis.io/docs/latest/commands/hgetall) for job metadata\n* [`EXPIRE`](https://redis.io/docs/latest/commands/expire) on completed and failed hashes for automatic cleanup\n* [`PUBLISH`](https://redis.io/docs/latest/commands/publish) on `queue:jobs:events` for completion signalling\n* [Lua scripting](https://redis.io/docs/latest/develop/programmability/eval-intro) ([`EVALSHA`](https://redis.io/docs/latest/commands/evalsha)) for the complete, fail, and reclaim flows so each runs atomically against the processing list and metadata hash" }, { "id": "enqueueing-jobs", "title": "Enqueueing jobs", "role": "content", "text": "`enqueue()` writes the metadata hash and pushes the job ID onto the pending list in one transaction (`MULTI` pipeline):\n\n[code example]\n\nThe payload is stored as JSON so the queue can carry arbitrary nested structures without forcing every field into a hash. Hash field values are all strings — `node-redis` won't convert numbers for you, so the helper coerces them explicitly." }, { "id": "claiming-jobs-with-blmove", "title": "Claiming jobs with BLMOVE", "role": "content", "text": "A worker blocks until a job is available, then atomically pops it from the pending list and pushes it onto the processing list. In Redis 6.2 and later this is `BLMOVE`; the older `BRPOPLPUSH` is deprecated and was removed from `node-redis` in v5:\n\n[code example]\n\n`BLMOVE pending processing RIGHT LEFT timeoutS` is the byte-for-byte equivalent of the old `BRPOPLPUSH pending processing timeoutS` — pop from the right end of pending, push onto the left end of processing, atomically, blocking up to `timeoutS` seconds.\n\nThe `claim_token` is the worker's proof of ownership for this attempt. Every subsequent state change (complete, fail) checks it before touching the processing list, so a worker that hung past the visibility timeout cannot interfere with the new claimant." }, { "id": "completing-jobs", "title": "Completing jobs", "role": "content", "text": "`complete()` runs a Lua script via `EVALSHA` so the processing-list removal, the metadata write, and the history push happen atomically:\n\n[code example]\n\nThe helper preloads each script with `SCRIPT LOAD` at first use and prefers `EVALSHA` to avoid resending the script body on every call. If Redis evicts the script cache and returns `NOSCRIPT`, the wrapper falls back to a full `EVAL` and re-caches the SHA.\n\nThe Lua script checks the token first and returns `0` if the worker no longer owns the job (because the reclaimer moved it back to pending). The metadata hash also gets an `EXPIRE` so completed jobs are cleaned up automatically." }, { "id": "failing-and-retrying", "title": "Failing and retrying", "role": "content", "text": "`fail()` either retries the job (back to pending) or moves it to the failed list once retries are exhausted:\n\n[code example]\n\nThe attempt counter is incremented on every `claim()`, so a job that fails three times is moved to the failed list with `attempts = 3` and the final `last_error` preserved." }, { "id": "reclaiming-stuck-jobs", "title": "Reclaiming stuck jobs", "role": "content", "text": "If a worker dies mid-job — the process is killed, the host loses power, the network partitions — the job sits in the processing list with a `claimed_at_ms` that never advances. A periodic call to `reclaimStuck()` walks the processing list and moves any job past the visibility timeout back to pending:\n\n[code example]\n\nThe Lua script also handles a narrower race: a worker that crashed between `BLMOVE` and writing `claimed_at_ms`. Those jobs are reclaimed after `2 × visibility_ms` using `enqueued_at_ms` as a fallback timer, so they aren't stranded forever." }, { "id": "stats-and-history", "title": "Stats and history", "role": "content", "text": "`stats()` reports queue depth plus per-process counters:\n\n[code example]\n\nThe completed and failed lists are capped via `LTRIM` so they never grow unbounded; a real deployment would also write completion events to a longer-term audit log if needed." }, { "id": "prerequisites", "title": "Prerequisites", "role": "content", "text": "* Redis 6.2 or later running locally on the default port (6379). Earlier versions still work for the rest of the pattern, but `BLMOVE` requires Redis 6.2+; on older servers swap it for `BRPOPLPUSH`.\n* Node.js 18 or later (the helper uses native `async`/`await` and the `crypto` module).\n* The `node-redis` client at version 5.x. Install it with:\n\n [code example]" }, { "id": "running-the-demo", "title": "Running the demo", "role": "content", "text": "" }, { "id": "get-the-source-files", "title": "Get the source files", "role": "content", "text": "The demo consists of four files. Download them from the [`nodejs` source folder](https://github.com/redis/docs/tree/main/content/develop/use-cases/job-queue/nodejs) on GitHub, or grab them with `curl`:\n\n[code example]\n\nThen install dependencies:\n\n[code example]" }, { "id": "start-the-demo-server", "title": "Start the demo server", "role": "content", "text": "From that directory:\n\n[code example]\n\nYou should see:\n\n[code example]\n\nOpen [http://127.0.0.1:8791](http://127.0.0.1:8791) in a browser. You can:\n\n* Enqueue jobs of different kinds (email, webhook, thumbnail, invoice) in batches.\n* Start a pool of workers with configurable size, work latency, and *failure* / *hang* rates. A non-zero hang rate simulates worker crashes.\n* Click **Run reclaim sweep** to move any timed-out processing jobs back to pending.\n* Watch pending / processing / completed / failed lists update every 800 ms.\n\nIf your Redis server is running elsewhere, start the demo with `--redis-host` and `--redis-port`. You can also tune the visibility timeout with `--visibility-ms` and the bind address with `--host` / `--port`." }, { "id": "the-mock-worker-pool", "title": "The mock worker pool", "role": "content", "text": "The demo includes a small `Worker` and `WorkerPool` ([source](https://github.com/redis/docs/blob/main/content/develop/use-cases/job-queue/nodejs/worker.js)) that stands in for whatever real background work your application would run. Each worker:\n\n* Blocks on `queue.claim()` for new jobs.\n* Sleeps `workLatencyMs` to simulate doing the work.\n* Either completes successfully, fails (calling `queue.fail()`), or *hangs* — returning without completing or failing the job so the reclaimer has to recover it.\n\nThe `failRate` and `hangRate` knobs let you watch the at-least-once delivery and reclaim behaviours from the UI without writing test code.\n\nBecause Node.js is single-threaded, each \"worker\" is an async loop running on the event loop rather than an OS thread. The `claim(500)` call uses Redis's blocking `BLMOVE` so the loop spends almost all its time waiting on the server rather than spinning; multiple workers share one Redis client and Node's I/O scheduler interleaves their claims naturally." }, { "id": "production-usage", "title": "Production usage", "role": "content", "text": "" }, { "id": "choose-a-visibility-timeout-that-matches-your-worst-case-job-latency", "title": "Choose a visibility timeout that matches your worst-case job latency", "role": "content", "text": "The visibility timeout has to exceed the longest real job time, with margin. If it's too short, a healthy worker that's running a slow job will get its work duplicated when the reclaimer fires. If it's too long, a real crash takes longer to detect. Most production deployments use a per-queue value tuned to the 99th-percentile job latency — for example, 2 minutes for email and 30 minutes for video transcoding." }, { "id": "run-the-reclaimer-on-a-schedule", "title": "Run the reclaimer on a schedule", "role": "content", "text": "The demo only reclaims when you click the button. In production, run `reclaimStuck()` from a periodic task (use `setInterval` for fast queues, or a separate scheduler process for slow ones), or from each worker before it blocks on `claim()`. Both patterns work as long as *someone* runs the sweep." }, { "id": "use-a-separate-redis-database-or-key-prefix-per-queue", "title": "Use a separate Redis database or key prefix per queue", "role": "content", "text": "The helper takes a `queueName` argument so you can run multiple independent queues against one Redis instance — for example, one queue per priority level, or one per job kind. Keep queue keys under a clearly-namespaced prefix (here, `queue:jobs:*`) so they're easy to inspect and easy to clear without touching application data." }, { "id": "cap-the-completed-and-failed-history", "title": "Cap the completed and failed history", "role": "content", "text": "The demo keeps the last 50 completed and 50 failed job IDs via `LTRIM`. If you need longer history for audit purposes, write completion events to a separate Redis Stream (or to an external store) and keep the in-queue history short. Stream consumer groups give you the same fan-out semantics with a much richer history." }, { "id": "tune-maxattempts-per-job-kind", "title": "Tune `maxAttempts` per job kind", "role": "content", "text": "A blanket `maxAttempts = 3` is a reasonable default for transient failures (network timeouts, rate limits). Jobs that talk to non-idempotent external systems — for example, posting a Stripe charge — need either application-level idempotency keys or a much lower retry count. The helper exposes `maxAttempts` so each queue can pick its own policy." }, { "id": "prefer-blmove-over-brpoplpush", "title": "Prefer `BLMOVE` over `BRPOPLPUSH`", "role": "content", "text": "`node-redis` v5 removed `client.brPopLPush()`; use `client.bLMove(src, dst, \"RIGHT\", \"LEFT\", timeoutSec)` instead. The two commands are functionally identical for this pattern: pop from the right of the source list and push onto the left of the destination list, atomically, blocking until a value appears. `BLMOVE` is more general (it accepts any combination of `LEFT`/`RIGHT` on either end) and is the recommended modern command." }, { "id": "use-one-shared-client-not-a-pool", "title": "Use one shared client, not a pool", "role": "content", "text": "`node-redis` pipelines commands automatically across a single TCP connection, so for most workloads you should create one `createClient()` instance per process and reuse it everywhere. The only reason to add a second connection is to dedicate one to a blocking call (such as `BLMOVE` with a long timeout, or `SUBSCRIBE`); this demo's `claim()` uses a short 500 ms timeout so a single client is fine." }, { "id": "inspect-queue-state-directly-in-redis", "title": "Inspect queue state directly in Redis", "role": "content", "text": "Because the queue is just lists and hashes, you can inspect it with `redis-cli`:\n\n[code example]" }, { "id": "learn-more", "title": "Learn more", "role": "related", "text": "This example uses the following Redis commands:\n\n* [`LPUSH`](https://redis.io/docs/latest/commands/lpush) to enqueue a job ID.\n* [`BLMOVE`](https://redis.io/docs/latest/commands/blmove) to atomically claim a job into the processing list (modern replacement for [`BRPOPLPUSH`](https://redis.io/docs/latest/commands/brpoplpush)).\n* [`LREM`](https://redis.io/docs/latest/commands/lrem) to remove a job from the processing list on complete or fail.\n* [`LRANGE`](https://redis.io/docs/latest/commands/lrange) and [`LLEN`](https://redis.io/docs/latest/commands/llen) to read queue depth and list contents.\n* [`LTRIM`](https://redis.io/docs/latest/commands/ltrim) to cap the completed and failed history.\n* [`HSET`](https://redis.io/docs/latest/commands/hset) and [`HGETALL`](https://redis.io/docs/latest/commands/hgetall) for job metadata.\n* [`HINCRBY`](https://redis.io/docs/latest/commands/hincrby) for the attempt counter.\n* [`EXPIRE`](https://redis.io/docs/latest/commands/expire) for automatic cleanup of completed and failed jobs.\n* [`PUBLISH`](https://redis.io/docs/latest/commands/publish) for job-completion notifications.\n* [`EVALSHA`](https://redis.io/docs/latest/commands/evalsha) for atomic complete, fail, and reclaim flows.\n\nSee the [`node-redis` documentation](https://redis.io/docs/latest/develop/clients/nodejs) for full client reference." } ], "examples": [ { "id": "the-job-queue-helper-ex0", "language": "javascript", "code": "const { createClient } = require(\"redis\");\nconst { RedisJobQueue } = require(\"./job_queue\");\n\nasync function main() {\n const client = createClient({ url: \"redis://localhost:6379\" });\n await client.connect();\n\n const queue = new RedisJobQueue({ redisClient: client, visibilityMs: 5000 });\n\n const jobId = await queue.enqueue({ kind: \"email\", recipient: \"alice@example.com\" });\n\n // In a worker process:\n const job = await queue.claim(1000);\n if (job !== null) {\n try {\n // ... run the job ...\n await queue.complete(job, { sent_at: \"2026-05-11T15:00:00Z\" });\n } catch (err) {\n await queue.fail(job, String(err));\n }\n }\n\n // In a periodic sweeper:\n const reclaimed = await queue.reclaimStuck();\n\n await client.quit();\n}\n\nmain().catch(console.error);", "section_id": "the-job-queue-helper" }, { "id": "data-model-ex0", "language": "text", "code": "queue:jobs:pending (list) pending job IDs, oldest at the right\nqueue:jobs:processing (list) claimed but not yet completed\nqueue:jobs:completed (list) recent successes (LTRIM-capped history)\nqueue:jobs:failed (list) terminally failed jobs\nqueue:jobs:job:{id} (hash) per-job metadata\nqueue:jobs:events (pubsub) completion notifications", "section_id": "data-model" }, { "id": "data-model-ex1", "language": "text", "code": "queue:jobs:job:9a4f...\n id = 9a4f...\n payload = {\"kind\":\"email\",\"recipient\":\"alice@example.com\"}\n status = pending | processing | completed | failed\n attempts = 1\n enqueued_at_ms = 1715441000000\n claimed_at_ms = 1715441000123\n claim_token = b3c0d1e2... (per-claim random token)\n completed_at_ms = 1715441000456\n result = {\"sent_at\":\"...\"}\n last_error = \"smtp timeout\"", "section_id": "data-model" }, { "id": "enqueueing-jobs-ex0", "language": "javascript", "code": "async enqueue(payload) {\n const jobId = crypto.randomBytes(8).toString(\"hex\");\n const nowMs = Date.now();\n const meta = {\n id: jobId,\n payload: JSON.stringify(payload),\n status: \"pending\",\n attempts: \"0\",\n enqueued_at_ms: String(nowMs),\n claim_token: \"\",\n };\n const multi = this.redis.multi();\n multi.hSet(this._metaKey(jobId), meta);\n multi.lPush(this.pendingKey, jobId);\n await multi.exec();\n this._enqueued += 1;\n return jobId;\n}", "section_id": "enqueueing-jobs" }, { "id": "claiming-jobs-with-blmove-ex0", "language": "javascript", "code": "async claim(timeoutMs = 1000) {\n const timeoutS = Math.max(timeoutMs / 1000, 0.1);\n const jobId = await this.redis.blMove(\n this.pendingKey,\n this.processingKey,\n \"RIGHT\",\n \"LEFT\",\n timeoutS,\n );\n if (jobId === null || jobId === undefined) {\n return null;\n }\n\n const token = crypto.randomBytes(8).toString(\"hex\");\n const nowMs = Date.now();\n const metaKey = this._metaKey(jobId);\n const multi = this.redis.multi();\n multi.hSet(metaKey, {\n status: \"processing\",\n claimed_at_ms: String(nowMs),\n claim_token: token,\n });\n multi.hIncrBy(metaKey, \"attempts\", 1);\n multi.hGetAll(metaKey);\n const results = await multi.exec();\n const meta = results[2] || {};\n return new ClaimedJob(jobId, JSON.parse(meta.payload || \"{}\"), Number(meta.attempts), token);\n}", "section_id": "claiming-jobs-with-blmove" }, { "id": "completing-jobs-ex0", "language": "javascript", "code": "async complete(job, result) {\n const ok = await this._evalScript(COMPLETE_SCRIPT, this._completeSha, {\n keys: [this.metaPrefix, this.processingKey, this.completedKey],\n arguments: [\n job.id,\n job.claimToken,\n \"completed\",\n String(Date.now()),\n JSON.stringify(result),\n String(this.completedTtl),\n String(this.completedHistory),\n ],\n });\n if (!ok || Number(ok) === 0) {\n return false;\n }\n await this.redis.publish(\n this.eventsChannel,\n JSON.stringify({ id: job.id, status: \"completed\" }),\n );\n this._completed += 1;\n return true;\n}", "section_id": "completing-jobs" }, { "id": "failing-and-retrying-ex0", "language": "javascript", "code": "async fail(job, error) {\n const retry = job.attempts < this.maxAttempts;\n const result = await this._evalScript(FAIL_SCRIPT, this._failSha, {\n keys: [this.metaPrefix, this.processingKey, this.pendingKey, this.failedKey],\n arguments: [\n job.id,\n job.claimToken,\n error,\n String(Date.now()),\n String(this.completedTtl),\n String(this.completedHistory),\n retry ? \"1\" : \"0\",\n ],\n });\n return Boolean(result) && Number(result) !== 0;\n}", "section_id": "failing-and-retrying" }, { "id": "reclaiming-stuck-jobs-ex0", "language": "javascript", "code": "async reclaimStuck() {\n const reclaimed = await this._evalScript(RECLAIM_SCRIPT, this._reclaimSha, {\n keys: [this.pendingKey, this.processingKey, this.metaPrefix],\n arguments: [String(Date.now()), String(this.visibilityMs)],\n });\n return Array.isArray(reclaimed) ? reclaimed : [];\n}", "section_id": "reclaiming-stuck-jobs" }, { "id": "stats-and-history-ex0", "language": "javascript", "code": "async stats() {\n const multi = this.redis.multi();\n multi.lLen(this.pendingKey);\n multi.lLen(this.processingKey);\n multi.lLen(this.completedKey);\n multi.lLen(this.failedKey);\n const [pending, processing, completed, failed] = await multi.exec();\n return {\n enqueued_total: this._enqueued,\n completed_total: this._completed,\n failed_total: this._failed,\n reclaimed_total: this._reclaimed,\n pending_depth: Number(pending) || 0,\n processing_depth: Number(processing) || 0,\n completed_depth: Number(completed) || 0,\n failed_depth: Number(failed) || 0,\n visibility_ms: this.visibilityMs,\n };\n}", "section_id": "stats-and-history" }, { "id": "prerequisites-ex0", "language": "bash", "code": "npm install redis", "section_id": "prerequisites" }, { "id": "get-the-source-files-ex0", "language": "bash", "code": "mkdir job-queue-demo && cd job-queue-demo\nBASE=https://raw.githubusercontent.com/redis/docs/main/content/develop/use-cases/job-queue/nodejs\ncurl -O $BASE/job_queue.js\ncurl -O $BASE/worker.js\ncurl -O $BASE/demoServer.js\ncurl -O $BASE/package.json", "section_id": "get-the-source-files" }, { "id": "get-the-source-files-ex1", "language": "bash", "code": "npm install", "section_id": "get-the-source-files" }, { "id": "start-the-demo-server-ex0", "language": "bash", "code": "node demoServer.js", "section_id": "start-the-demo-server" }, { "id": "start-the-demo-server-ex1", "language": "text", "code": "Redis job-queue demo server listening on http://127.0.0.1:8791\nUsing Redis at localhost:6379\nVisibility timeout: 5000 ms", "section_id": "start-the-demo-server" }, { "id": "inspect-queue-state-directly-in-redis-ex0", "language": "bash", "code": "# How many pending jobs?\nredis-cli LLEN queue:jobs:pending\n\n# Look at the next 5 jobs to be picked up.\nredis-cli LRANGE queue:jobs:pending -5 -1\n\n# Read a job's metadata.\nredis-cli HGETALL queue:jobs:job:9a4f0d1c\n\n# How many jobs are currently being processed?\nredis-cli LLEN queue:jobs:processing\n\n# Clear everything for this queue (be careful — this deletes work).\nredis-cli --scan --pattern 'queue:jobs:*' | xargs redis-cli DEL", "section_id": "inspect-queue-state-directly-in-redis" } ] }