Redis Timeout: Diagnosis
Identify and resolve Redis connection problems.
Redis is used for caching and sessions. When Redis times out, the entire application slows or crashes. Here's how to diagnose and resolve these problems.
Symptoms
- "Connection timed out" errors to Redis
- Response time that suddenly increases
- Lost sessions or ignored cache
- "Redis connection refused" errors
Common Causes
- Redis overloaded: Too many operations or blocking commands (KEYS *).
- Memory full: Redis reaches maxmemory and evicts or refuses writes.
- Unstable network: Network latency between app and Redis, especially on remote services.
Diagnostic Steps
- Test connectivity with redis-cli ping
- Check memory with INFO memory
- Analyze slow commands (SLOWLOG GET 10)
- Check connection count (INFO clients)
Automate with MoniTao
MoniTao detects Redis problem effects:
- Monitoring of application response times
- Alerts on sudden 500 errors
- Heartbeat for jobs using Redis
Best Practices
- Avoid KEYS * in production, use SCAN
- Configure maxmemory with an eviction policy
- Use an appropriate connection timeout
- Implement a fallback if Redis is unavailable
FAQ
What timeout to configure?
Connection: 2-5s. Command: depends on operation. Avoid 0 (infinite).
What if Redis is full?
Increase maxmemory or configure an eviction policy (allkeys-lru).
Sentinel or Cluster?
Sentinel for simple high availability. Cluster for horizontal scaling.
Can MoniTao monitor Redis directly?
No, but it monitors impact on your application (response times, errors).
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