CRE-2025-0175
Redis Master-Replica Synchronization FailureCriticalImpact: 8/10Mitigation: 6/10
Description
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.\n
Mitigation
IMMEDIATE ACTIONS:\n- Check replication status: `redis-cli INFO replication`\n- Verify replica connectivity: `redis-cli -h replica ping`\n- Monitor sync progress: `redis-cli INFO | grep master_sync`\n- Check replication lag: `redis-cli INFO | grep master_repl_offset`\n\nRECOVERY:\n- Restart replication on replica:\n ```\n redis-cli REPLICAOF NO ONE\n redis-cli REPLICAOF master-host master-port\n ```\n- Increase replication backlog:\n `redis-cli CONFIG SET repl-backlog-size 256mb`\n- Adjust replica output buffer:\n `redis-cli CONFIG SET client-output-buffer-limit "replica 256mb 64mb 60"`\n- Force full resync if partial sync fails:\n `redis-cli PSYNC replicationid -1`\n\nTROUBLESHOOTING:\n- Check network latency: `ping -c 100 master-host`\n- Monitor disk I/O: `iostat -x 1`\n- Review Redis logs: `tail -f /var/log/redis/redis-server.log`\n- Verify firewall rules allow port 6379\n\nPREVENTION:\n- Size replication backlog appropriately\n- Monitor replication lag metrics\n- Use dedicated network for replication\n- Optimize disk I/O on replicas\n- Regular testing of failover procedures\n- Keep master and replica versions in sync\n