Essential Redis Monitoring Metrics Every Engineer Should Know

Monitoring Metrics

Performance

Memory

Basic activity

Persistence

Error

Performance Metrics

latency : Redis response time for a request.

instantaneous_ops_per_sec : Average number of operations processed per second.

hi rate (calculated) : Calculated cache hit rate.

Memory Metrics

used_memory : Amount of memory currently 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 replicas.

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 persistence to disk.

rdb_changes_since_last_save : Number of changes since the last persistence.

Error Metrics

rejected_connections : Connections rejected because maxclients limit was reached.

keyspace_misses : Number of key look‑ups that missed (no hit).

master_link_down_since_seconds : Duration (in seconds) that the master‑slave link has been down.

Monitoring Methods

redis-benchmark

redis-stat

redis-faina

redislive

redis-cli

monitor

showlog

slowlog commands (get, len, reset)

Configuration Snippets

slowlog-log-slower-than 1000 # set slow‑query threshold in microseconds</code>
<code>slowlog-max-len 100 # set max number of slow‑query log entries

Using the INFO Command

Info can retrieve all sections at once or specific sections such as server, clients, memory, persistence, stats, Replication, CPU, cluster, and Keyspace.

./redis-cli info | grep ops          # operations per second

Performance Monitoring

redis-cli info | grep ops

Memory Monitoring

./redis-cli info | grep used_memory_human</code>
<code>used_memory_human:2.99M  # memory allocated from OS</code>
<code>used_memory_rss_human:8.04M # memory seen by OS (top)</code>
<code>used_memory_peak_human:7.77M # peak memory consumption</code>
<code>used_memory_lua_human:37.00K # Lua engine memory

./redis-cli info | grep blocked_clients</code>
<code>blocked_clients:0

./redis-cli info | grep evicted_keys</code>
<code>evicted_keys:0

./redis-cli info | grep mem_fragmentation_ratio</code>
<code>mem_fragmentation_ratio:2.74

./redis-cli info | grep used_memory</code>
<code>used_memory:3133624

Basic Activity Monitoring

./redis-cli info | grep connected_clients</code>
<code>connected_clients:1</code>
<code>connected_slaves:1

Persistence Monitoring

./redis-cli info | grep rdb_last_save_time</code>
<code>rdb_last_save_time:1591876204</code>
<code>./redis-cli info | grep rdb_changes_since_last_save</code>
<code>rdb_changes_since_last_save:0

Error Monitoring

./redis-cli info | grep rejected_connections</code>
<code>rejected_connections:0

./redis-cli info | grep keyspace_misses</code>
<code>keyspace_misses:0

./redis-cli info | grep master_link_down_since_seconds</code>
<code>master_link_down_since_seconds:0

Redis Performance Test Command

./redis-benchmark -c 100 -n 5000

Runs a benchmark with 100 concurrent connections and 5,000 total requests.