n8n - 💡(How to fix) Fix Task runner grant token TTL (15s) too short for low-power hardware — causes 100%+ CPU retry loop [1 comments, 2 participants]

Bug Description

On low-power hardware (Intel N150, 4 cores), the external task runner consistently fails to authenticate with the task broker because the grant token expires before the runner process can spawn and connect.

The grant token TTL is hardcoded to 15 seconds in task-broker-auth.service.js:

const GRANT_TOKEN_TTL = 15 * constants_1.Time.seconds.toMilliseconds;

There is no environment variable or configuration option to change this value.

On slower hardware, the runner takes >15s to:

1. Receive the grant token from the broker
2. Spawn the Node.js/Python process
3. Establish the WebSocket upgrade using the token

This causes a tight retry loop:

• Broker issues grant token → token expires before runner connects → 403 → broker issues new token → repeat
• The retry loop consumes 100%+ CPU continuously, making the entire system unusable
• Both internal and external runners are affected identically

To Reproduce

1. Deploy n8n v2.14.2 with an external task runner on low-power hardware (Intel N150, Celeron, Atom, or similar)
2. Trigger any workflow that uses a Code node
3. Observe the runner failing with 403 errors in a tight loop
4. CPU usage spikes to 100%+ and stays there

Expected behavior

• The grant token TTL should be configurable via an environment variable (e.g., N8N_RUNNERS_GRANT_TOKEN_TTL=120)
• The default of 15 seconds is reasonable for fast hardware, but there should be a way to increase it for slower systems
• Alternatively, the runner could use a backoff strategy instead of tight retries on 403

Current workaround

Volume-mount a patched task-broker-auth.service.js with a higher TTL:

volumes:
  - ./patches/task-broker-auth.service.js:/usr/local/lib/node_modules/n8n/dist/task-runners/task-broker/auth/task-broker-auth.service.js:ro

This is fragile and breaks on version updates.

Debug Info

• n8nVersion: 2.14.2
• platform: docker (self-hosted)
• database: PostgreSQL
• executionMode: main (default)
• hardware: Intel N150 (4 cores, 12GB RAM)
• runner mode: external (n8nio/runners:2.14.2)

Operating System

Linux (Debian 12)

n8n Version

2.14.2

Node.js Version

22.x

Database

PostgreSQL

Execution mode

main (default)

Hosting

self hosted