Mastering Redis Monitoring: Key Metrics, Commands, and Performance Tips

Monitoring Metrics

Redis provides several categories of monitoring metrics: Performance, Memory, Basic activity, Persistence, and Error.

Performance Metrics

latency : Time Redis takes to respond to a request.

instantaneous_ops_per_sec : Average number of operations processed per second.

hit_rate (calculated) : Cache hit rate.

Memory Metrics

used_memory : Amount of memory used.

mem_fragmentation_ratio : Memory fragmentation ratio.

evicted_keys : Number of keys evicted due to maxmemory limit.

blocked_clients : Clients blocked by BLPOP/BRPOP/BRPOPLPUSH.

Basic Activity Metrics

connected_clients : Number of client connections.

connected_slaves : Number of slave connections.

master_last_io_seconds_ago : Seconds since last master‑slave interaction.

keyspace : Total number of keys in the database.

Persistence Metrics

rdb_last_save_time : Timestamp of the last RDB save.

rdb_changes_since_last_save : Number of changes since the last save.

Error Metrics

rejected_connections : Connections rejected because maxclients limit was reached.

keyspace_misses : Number of key lookups that missed.

master_link_down_since_seconds : Duration of master‑slave link down.

Monitoring Tools

Common Redis monitoring utilities include redis‑benchmark, redis‑stat, redis‑faina, redislive, redis‑cli, monitor, and showlog.

Slowlog Configuration

slowlog-log-slower-than 1000   # set slow query threshold in microseconds
slowlog-max-len 100           # set number of entries to keep

Using the INFO Command

The redis-cli info command can retrieve all sections or specific sections such as server, clients, memory, persistence, stats, replication, CPU, cluster, and keyspace.

Example Commands

redis-cli info | grep ops               # operations per second
redis-cli info memory | grep used_memory_human
redis-cli info stats | grep ops
./redis-benchmark -c 100 -n 5000        # performance test: 100 connections, 5000 requests