redis-operations

Skill: Redis Operations

Expertise: Redis memory management, eviction, persistence (RDB+AOF), Redis Sentinel, Redis Cluster, K8s Redis (Bitnami/Spotahome operator).

When to load

When investigating Redis memory pressure, configuring persistence, debugging eviction, or setting up Redis HA.

Health Check Commands

# Connect to Redis
redis-cli -h redis-master -p 6379 -a $REDIS_PASSWORD

# Server info overview
redis-cli INFO server | grep -E "redis_version|uptime|tcp_port"
redis-cli INFO memory | grep -E "used_memory_human|used_memory_peak_human|mem_fragmentation_ratio|maxmemory"
redis-cli INFO stats   | grep -E "total_commands_processed|rejected_connections|evicted_keys"
redis-cli INFO keyspace  # databases with key counts + expires

# Real-time monitoring (ops/sec per command)
redis-cli --stat          # 1-second interval stats
redis-cli MONITOR         # log every command (NEVER in production for long — high overhead)

# Slow log (commands over threshold)
redis-cli CONFIG SET slowlog-log-slower-than 10000   # 10ms threshold
redis-cli SLOWLOG GET 20   # last 20 slow commands
redis-cli SLOWLOG LEN
redis-cli SLOWLOG RESET

Memory Management

# Check memory usage breakdown
redis-cli MEMORY DOCTOR        # health analysis + recommendations
redis-cli MEMORY STATS         # detailed breakdown
redis-cli MEMORY USAGE <key>   # bytes used by a specific key

# Find big keys (scan, not KEYS — non-blocking)
redis-cli --bigkeys            # sample-based big key finder
redis-cli --memkeys            # memory usage per key (sample)

# Memory fragmentation: ratio > 1.5 = fragmentation, < 1.0 = swap
redis-cli INFO memory | grep mem_fragmentation_ratio

# Defragment memory online (Redis 4+)
redis-cli CONFIG SET activedefrag yes
redis-cli CONFIG SET active-defrag-threshold-lower 10   # start at 10% frag

Eviction Policy

# View current policy
redis-cli CONFIG GET maxmemory-policy

# Set eviction policy
# allkeys-lru    — evict any key by LRU (general-purpose cache)
# volatile-lru   — evict only keys with TTL by LRU (mixed TTL/no-TTL use)
# allkeys-lfu    — evict by LFU (access frequency, Redis 4+) — best for skewed access
# noeviction     — return OOM error when full (use for session store / queue — no silent data loss)
redis-cli CONFIG SET maxmemory-policy allkeys-lru

# Set memory limit
redis-cli CONFIG SET maxmemory 4gb

# Persist config to redis.conf
redis-cli CONFIG REWRITE