render-oss/render-background-workers

Render Background Workers

This skill explains worker services on Render: processes that consume jobs from a queue instead of serving HTTP. Pair with render-blueprints, render-env-vars, and render-networking when wiring render.yaml and private connectivity.

When to Use

• Designing or debugging queue-backed workers (Celery, Sidekiq, BullMQ, Asynq, etc.)
• Choosing between a worker, Cron Job, or Workflow for background work
• Configuring Render Key Value as a broker (not a cache) with correct eviction policy
• Implementing graceful shutdown so in-flight jobs are not lost on deploy

Per-framework setup and signal-handling detail: references/queue-framework-setup.md, references/graceful-shutdown.md.

How Workers Work

• Long-running services with no inbound (HTTP) traffic. Render does not expose a public URL or internal hostname for workers the way it does for web or private services—workers cannot receive private network traffic directed at them.
• The typical pattern is a poll loop: the process connects to a queue backend (often Render Key Value, Redis-compatible Valkey 8) and pulls jobs.
• Workers can initiate outbound connections on the private network—to PostgreSQL, Key Value, private services, web services (internal URLs), and the public internet—subject to your plan and firewall rules.

Queue Framework Overview

| Framework | Language | Queue backend | Notes | |-----------|----------|---------------|--------| | Celery | Python | Redis / Key Value | Most common Python task queue | | Sidekiq | Ruby | Redis / Key Value | Standard for Rails | | BullMQ | Node.js | Redis / Key Value | Modern Node queue (Redis-based) | | Asynq | Go | Redis / Key Value | Go async task processing | | Oban | Elixir | Postgres (not Redis) | Queue stored in the database |

Pairing with Key Value

• Use Render Key Value as the job broker when your framework expects Redis.
• Set maxmemory policy to noeviction. allkeys-lru and similar policies are for caches; evicting queue keys drops jobs.
• Wire REDIS_URL (or your framework’s equivalent) via fromService with type: keyvalue and property: connectionString in the Blueprint.
• Blueprints require ipAllowList on Key Value—include the CIDRs that should reach the instance (often [] for private-network-only access; see render-blueprints / Key Value field reference).

See references/queue-framework-setup.md for minimal app + YAML examples.

Worker vs Cron vs Workflow

| Need | Use | Why | |------|-----|-----| | Always-on queue consumer | Background Worker | Polls continuously; long-lived process | | Periodic scheduled task | Cron Job | Runs on a schedule, exits; 12h max per run | | Distributed parallel compute | Workflow | Each run gets its own instance; fan-out patterns | | High-volume or bursty jobs | Workflow | Scales per run; no idle instance cost between runs |

Graceful Shutdown

• Before stopping an instance, Render sends SIGTERM, then waits up to maxShutdownDelaySeconds (1–300, default 30) before SIGKILL.
• Workers should: (1) stop accepting new jobs, (2) finish the current job or checkpoint progress, (3) close connections, (4) exit 0.
• Set maxShutdownDelaySeconds to at least your longest safe job duration (see Dashboard or Blueprint).

Language- and framework-specific handlers: references/graceful-shutdown.md.

Blueprint Configuration

Minimal pattern: type: worker, runtime, buildCommand, startCommand, and envVars wired from Key Value.

services:
  - type: keyvalue
    name: jobs
    plan: starter
    region: oregon
    ipAllowList: []

  - type: worker
    name: task-worker
    runtime: python
    region: oregon
    plan: starter
    buildCommand: pip install -r requirements.txt
    startCommand: celery -A tasks worker --loglevel=info
    envVars:
      - key: REDIS_URL
        fromService:
          name: jobs
          type: keyvalue
          property: connectionString

Optional: maxShutdownDelaySeconds on the worker service for longer draining jobs.

References

| Topic | File | |--------|------| | Celery, Sidekiq, BullMQ, Asynq, Oban setup + YAML | references/queue-framework-setup.md | | SIGTERM, maxShutdownDelaySeconds, per-language patterns | references/graceful-shutdown.md |

Related Skills

• render-deploy — First deploy, CLI, service creation
• render-blueprints — Full render.yaml schema, fromService, projects
• render-networking — Private URLs, what can call what
• render-scaling — Worker plans, instance counts, limits