Essential Redis Monitoring Metrics Every Engineer Should Know

Monitoring Metrics

Performance

Memory

Basic activity

Persistence

Error

Performance Metrics

latency : Time Redis takes to respond to 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 connections.

master_last_io_seconds_ago : Seconds since the last master‑slave interaction.

keyspace : Total number of keys in the database.

Persistence Metrics

rdb_last_save_time : Timestamp of the last RDB persistence.

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.

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)

Key

info

command can retrieve all sections or specific blocks such as

server

,

clients

,

memory

,

persistence

,

stats

,

replication

,

cpu

,

cluster

,

keyspace

.

slowlog-log-slower-than 1000   # set slow‑query threshold (µs)

slowlog-max-len 100          # max number of slow‑query entries

Example commands:

# Get all info and filter
redis-cli info | grep ops

# Memory usage (human readable)
redis-cli info | grep used | grep human

# Blocked clients
redis-cli info | grep blocked_clients

# Evicted keys
redis-cli info | grep evicted_keys

# Memory fragmentation ratio
redis-cli info | grep mem_fragmentation_ratio

# Used memory
redis-cli info | grep used_memory

Performance Testing

redis-benchmark -c 100 -n 5000   # 100 connections, 5000 requests

Resulting chart illustrates operations per second:

Original source: blog.51cto.com/yht1990/2503819