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title: "Redis Connection Timeout and Connectivity Issues"
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category: "in-memory-database-problem"
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author: Prequel Community
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description: |
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Detects Redis connection timeout errors and connectivity failures that prevent clients from establishing or maintaining connections to the Redis server. These issues commonly occur during high load, network problems, or server resource exhaustion.
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cause: |
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- Network latency or packet loss between client and Redis server
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- Redis server CPU overload causing slow response times
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- Client connection pool exhaustion or misconfiguration
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- Firewall or security group blocking connections
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- Redis server reached max clients limit
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- DNS resolution failures
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- Redis server process crashed or unresponsive
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impact: |
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- Application unable to read/write cache data
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- Increased latency for user requests
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- Potential data inconsistency if writes fail silently
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- Backend database overload due to cache unavailability
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- Service degradation or complete outage
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- Connection pool exhaustion leading to thread blocking
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impactScore: 10
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tags:
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- redis
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- connection
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- timeout
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- connectivity
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- network
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mitigation: |
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IMMEDIATE ACTIONS:
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- Verify Redis server is running: `systemctl status redis`
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- Test connectivity: `redis-cli -h <host> -p <port> ping`
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- Check current connections: `redis-cli CLIENT LIST | wc -l`
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- Review max clients setting: `redis-cli CONFIG GET maxclients`
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RECOVERY:
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- Restart Redis service if unresponsive:
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`systemctl restart redis`
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- Increase connection timeout in client:
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`redis.conf: timeout 300`
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- Kill idle connections:
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`redis-cli CLIENT KILL TYPE normal`
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- Increase max clients limit:
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`redis-cli CONFIG SET maxclients 10000`
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NETWORK TROUBLESHOOTING:
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- Check firewall rules: `iptables -L -n`
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- Test network connectivity: `telnet redis-host 6379`
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- Verify DNS resolution: `nslookup redis-host`
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- Check for packet loss: `ping -c 100 redis-host`
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PREVENTION:
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- Implement connection pooling with proper sizing
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- Configure appropriate timeout values
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- Monitor connection metrics and set alerts
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- Use Redis Sentinel or Cluster for high availability
title: "Redis Authentication Failures and ACL Permission Denials"
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category: "in-memory-database-problem"
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author: Prequel Community
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description: |
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Detects Redis authentication failures including wrong passwords, missing authentication, and ACL permission denials. These errors prevent legitimate clients from accessing Redis and may indicate security misconfigurations or attempted unauthorized access.
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cause: |
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- Incorrect password provided by client
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- Redis requirepass configured but client not sending auth
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- ACL user lacks required permissions for commands
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- Password rotation without updating client configs
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- Expired or disabled ACL user accounts
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- Misconfigured Redis AUTH settings
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impact: |
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- Complete inability to access Redis cache/data
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- Application features dependent on Redis fail
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- Service outages if Redis is critical infrastructure
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- Security risk if authentication is bypassed
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- Potential data exposure if misconfigured
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tags:
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- redis
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- authentication
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- security
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- acl
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- wrongpass
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mitigation: |
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IMMEDIATE ACTIONS:
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- Verify Redis auth configuration: `redis-cli CONFIG GET requirepass`
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- Test authentication: `redis-cli -a <password> ping`
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- Check ACL users: `redis-cli ACL LIST`
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- Review client connection strings for correct credentials
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RECOVERY:
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- Update client password configuration
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- Reset Redis password if needed:
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`redis-cli CONFIG SET requirepass newpassword`
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- Fix ACL permissions for user:
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`redis-cli ACL SETUSER username +@all`
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- Disable auth temporarily (UNSAFE):
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`redis-cli CONFIG SET requirepass ""`
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ACL TROUBLESHOOTING:
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- List user permissions: `redis-cli ACL GETUSER username`
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- Grant specific command access:
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`redis-cli ACL SETUSER username +get +set +del`
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- Create new user with full access:
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`redis-cli ACL SETUSER newuser on >password +@all`
Detects failures in Redis master-replica synchronization including broken replication links, sync timeouts, and full resync loops. These issues compromise data consistency and high availability in Redis deployments.
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cause: |
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- Network partition between master and replica
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- Replica unable to keep up with master write load
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- Insufficient replica output buffer size
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- Master rewrite of AOF/RDB during sync
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- Replica disk I/O too slow for sync
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- Version incompatibility between master and replica
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- Replication backlog size too small
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impact: |
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- Replicas serve stale or inconsistent data
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- Failover capability compromised
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- Read scaling degraded with out-of-sync replicas
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- Full resync causing performance impact
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- Potential data loss during failover
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- Increased load on master during resync attempts
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tags:
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- redis
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- replication
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- master-replica
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- sync
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- psync
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mitigation: |
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IMMEDIATE ACTIONS:
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- Check replication status: `redis-cli INFO replication`
title: "Redis Persistence Failure - MISCONF Disk Write Errors"
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category: "in-memory-database-problem"
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author: Prequel Community
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description: |
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Detects Redis MISCONF errors when the server cannot persist data to disk due to RDB/AOF write failures. This critical error prevents Redis from saving snapshots and may lead to data loss on restart.
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cause: |
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- Disk full or insufficient space for RDB/AOF files
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