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Overview

ondoki uses Redis 7 for three purposes:
  1. Caching — session data and temporary state (DB 0)
  2. WebSocket pub/sub — real-time notification delivery across multiple backend instances
  3. Celery broker — task queue for async media processing jobs (DB 1)

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Docker Setup

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Development

redis:
  image: redis:7-alpine
  container_name: ondoki-redis
  restart: unless-stopped
No password required in development.

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Production

redis:
  image: redis:7-alpine
  container_name: ondoki-redis
  restart: unless-stopped
  command: >
    redis-server
    --requirepass ${REDIS_PASSWORD:-}
    --maxmemory 256mb
    --maxmemory-policy allkeys-lru
  healthcheck:
    test: ["CMD", "redis-cli", "-a", "${REDIS_PASSWORD:-}", "ping"]
    interval: 10s
    timeout: 5s
    retries: 3
Production configuration:
  • Password authentication via REDIS_PASSWORD
  • Memory limit of 256 MB with LRU eviction
  • Health checks every 10 seconds

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Connection Strings

ondoki uses two Redis databases:
PurposeDBVariableDefault
Cache + pub/sub0REDIS_URLredis://redis:6379/0
Celery broker1CELERY_BROKER_URLredis://redis:6379/1
Celery results1CELERY_RESULT_BACKENDredis://redis:6379/1
In production with a password: 
REDIS_URL=redis://:yourpassword@redis:6379/0
CELERY_BROKER_URL=redis://:yourpassword@redis:6379/1
CELERY_RESULT_BACKEND=redis://:yourpassword@redis:6379/1

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WebSocket Notifications

The backend uses Redis pub/sub for real-time notifications to connected clients (e.g., desktop apps). This enables multi-server support — notifications published by one backend instance are delivered to WebSocket clients connected to any instance. Channel: notifications are published per-user using the user ID as the channel key.

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Celery Task Queue

The Celery media worker processes async jobs:
  • Video import processing (frame extraction, transcription, guide generation)
  • Queues: celery, media
  • Concurrency: 1 worker (video processing is CPU/memory intensive)

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External Redis

To use an external Redis instance:
  1. Set REDIS_URL, CELERY_BROKER_URL, and CELERY_RESULT_BACKEND to your external Redis connection strings
  2. Remove the redis service from your Docker Compose file
  3. Ensure the external Redis supports pub/sub (required for WebSocket notifications)

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Persistence

The default configuration does not persist Redis data to disk. This is acceptable because:
  • Session data is also stored in PostgreSQL
  • Celery tasks are transient
  • WebSocket pub/sub is ephemeral
If you need Redis persistence, add a volume and configure RDB/AOF in your Redis configuration.