Check redis-status

Overview

Monitors a Redis server via the INFO command, reporting memory usage, fragmentation ratio, keyspace hit rate, connected clients, replication status, and persistence state.

Important Notes:

• Tested on Redis 3.0+

• Requires the redis-cli command-line tool

• „I’m here to keep you safe, Sam. I want to help you.“ comes from the character GERTY in the movie „Moon“ (2009)

Data Collection:

• Executes redis-cli info default and redis-cli memory doctor against the target Redis instance

• Connects via hostname/port (default: 127.0.0.1:6379) or Unix socket

• Supports authentication (username/password) and TLS connections

• Reads OS-level settings from /proc/sys/vm/overcommit_memory, /sys/kernel/mm/transparent_hugepage/enabled, /proc/sys/net/core/somaxconn, and /proc/sys/net/ipv4/tcp_max_syn_backlog

Fact Sheet

Fact	Value
Check Plugin Download	https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/redis-status
Nagios/Icinga Check Name	check_redis_status
Check Interval Recommendation	Every minute
Can be called without parameters	Yes
Runs on	Linux
Compiled for Windows	No
Requirements	command-line tool redis-cli

Help

usage: redis-status [-h] [-V] [--always-ok] [--cacert CACERT] [-c CRIT]
                    [-H HOSTNAME] [--ignore-maxmemory0] [--ignore-overcommit]
                    [--ignore-somaxconn] [--ignore-sync-partial-err]
                    [--ignore-thp] [-p PASSWORD] [--port PORT]
                    [--socket SOCKET] [--test TEST] [--tls]
                    [--username USERNAME] [--verbose] [-w WARN]

Monitors a Redis server via the INFO command. Reports memory usage,
fragmentation ratio, keyspace hit rate, connected clients, replication status,
and persistence state. Alerts on memory consumption, high fragmentation, low
hit rates, and OS-level misconfigurations such as overcommit and transparent
huge pages. Includes Redis Memory Doctor diagnostics when available.

options:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  --always-ok           Always returns OK.
  --cacert CACERT       CA certificate file for TLS verification. Requires
                        `--tls`. Default: /etc/pki/tls/certs/rootCA.pem
  -c, --critical CRIT   CRIT threshold for memory usage as a percentage.
                        Default: >= None
  -H, --hostname HOSTNAME
                        Redis server hostname. Default: 127.0.0.1
  --ignore-maxmemory0   Suppress the warning when Redis maxmemory is set to 0
                        (unlimited). Default: False
  --ignore-overcommit   Suppress the warning when vm.overcommit_memory is not
                        set to 1. Default: False
  --ignore-somaxconn    Suppress the warning when net.core.somaxconn is lower
                        than net.ipv4.tcp_max_syn_backlog. Default: False
  --ignore-sync-partial-err
                        Suppress the warning about partial sync errors. Useful
                        for asynchronous replication setups where a small
                        number of "denied partial resync requests" is
                        expected. Default: False
  --ignore-thp          Suppress the warning about transparent huge pages
                        being enabled. Default: False
  -p, --password PASSWORD
                        Password for Redis server authentication.
  --port PORT           Redis server port. Default: 6379
  --socket SOCKET       Redis server Unix socket path. Overrides --hostname
                        and --port.
  --test TEST           For unit tests. Needs "path-to-stdout-file,path-to-
                        stderr-file,expected-retc".
  --tls                 Establish a secure TLS connection to Redis.
  --username USERNAME   Username for Redis server authentication.
  --verbose             Makes this plugin verbose during the operation. Useful
                        for debugging and seeing what is going on under the
                        hood. Default: False
  -w, --warning WARN    WARN threshold for memory usage as a percentage.
                        Default: >= 90

Usage Examples

./redis-status \
    --ignore-maxmemory0 \
    --ignore-overcommit \
    --ignore-somaxconn \
    --ignore-sync-partial-err \
    --ignore-thp \
    --username=linus \
    --password=linuxfabrik

Output:

Redis v5.0.3, standalone mode on 127.0.0.1:6379, /etc/redis.conf, up 4m 25s, 100.9% memory usage
[WARNING] (9.6MiB/9.5MiB, 9.6MiB peak, 19.6MiB RSS), maxmemory-policy=noeviction, 3 DBs
(db0 db3 db4) with 10 keys, 0.0 evicted keys, 0.0 expired keys, hit rate 100.0%
(3.0M hits, 0.0 misses), vm.overcommit_memory is not set to 1, kernel transparent_hugepage is not
set to "madvise" or "never", net.core.somaxconn (128) is lower than net.ipv4.tcp_max_syn_backlog
(256). Sam, I detected a few issues in this Redis instance memory implants:

 * High total RSS: This instance has a memory fragmentation and RSS overhead greater than 1.4
 (this means that the Resident Set Size of the Redis process is much larger than the sum of the
logical allocations Redis performed). This problem is usually due either to a large peak
memory (check if there is a peak memory entry above in the report) or may result from a workload
that causes the allocator to fragment memory a lot. If the problem is a large peak memory, then
there is no issue. Otherwise, make sure you are using the Jemalloc allocator and not the default
libc malloc. Note: The currently used allocator is "jemalloc-5.1.0".

I'm here to keep you safe, Sam. I want to help you.

States

• OK if memory usage is below the warning threshold and no OS-level misconfigurations are detected.

• WARN or CRIT if memory usage exceeds the configured thresholds (default: WARN >= 90%).

• WARN when maxmemory is set to 0 (unlimited), unless suppressed via --ignore-maxmemory0.

• WARN on memory issues reported by Redis Memory Doctor (except harmless peak-only or jemalloc cases).

• WARN on partial sync errors, unless suppressed via --ignore-sync-partial-err.

• WARN on OS-level misconfigurations (vm.overcommit_memory, transparent huge pages, somaxconn), each individually suppressible.

• --always-ok suppresses all alerts and always returns OK.

Perfdata / Metrics

Latest info can be found here.

Name	Type	Description
clients_blocked_clients	Number	Number of clients pending on a blocking call
clients_connected_clients	Number	Number of client connections (excluding connections from replicas)
cpu_used_cpu_sys	Number	System CPU consumed by the Redis server, which is the sum of system CPU consumed by all threads of the server process (main thread and background threads)
cpu_used_cpu_sys_children	Number	System CPU consumed by the background processes
cpu_used_cpu_user	Number	User CPU consumed by the Redis server, which is the sum of user CPU consumed by all threads of the server process (main thread and background threads)
cpu_used_cpu_user_children	Number	User CPU consumed by the background processes
db_count	Number	Number of Redis databases
key_count	Number	Sum of all keys across all databases
keyspace_DBNAME_avg_ttl	Seconds	Average TTL for keys in this database
keyspace_DBNAME_expires	Number	The number of keys with an expiration
keyspace_DBNAME_keys	Number	The number of keys
keyspace_hit_rate	Percentage	Percentage of key lookups that are successfully returned by keys in your Redis instance
mem_usage	Percentage	How close the working set size is to reaching the maxmemory limit
memory_maxmemory	Bytes	Configured maximum memory limit
memory_mem_fragmentation_ratio	Number	Ratio between used_memory_rss and used_memory
memory_total_system_memory	Bytes	The total amount of memory that the Redis host has
memory_used_memory	Bytes	Total number of bytes allocated by Redis using its allocator
memory_used_memory_lua	Bytes	Number of bytes used by the Lua engine
memory_used_memory_rss	Bytes	Number of bytes that Redis allocated as seen by the operating system (resident set size)
persistance_aof_current_rewrite_time_sec	Seconds	Duration of the on-going AOF rewrite operation if any
persistance_aof_rewrite_in_progress	Number	Flag indicating an AOF rewrite operation is on-going
persistance_aof_rewrite_scheduled	Number	Flag indicating an AOF rewrite operation will be scheduled once the on-going RDB save is complete
persistance_loading	Number	Flag indicating if the load of a dump file is on-going
persistance_rdb_bgsave_in_progress	Number	Flag indicating a RDB save is on-going
persistance_rdb_changes_since_last_save	Number	Number of changes since the last dump
persistance_rdb_current_bgsave_time_sec	Seconds	Duration of the on-going RDB save operation if any
replication_connected_slaves	Number	Number of connected replicas
replication_repl_backlog_histlen	Bytes	Size in bytes of the data in the replication backlog buffer
replication_repl_backlog_size	Bytes	Total size in bytes of the replication backlog buffer
server_uptime_in_seconds	Seconds	Number of seconds since Redis server start
stats_evicted_keys	Continuous Counter	Number of evicted keys due to maxmemory limit
stats_expired_keys	Continuous Counter	Total number of key expiration events
stats_instantaneous_input	Number	The network read rate per second in KB/sec
stats_instantaneous_ops_per_sec	Number	Number of commands processed per second
stats_instantaneous_output	Number	The network write rate per second in KB/sec
stats_keyspace_hits	Number	Number of successful lookup of keys in the main dictionary
stats_keyspace_misses	Number	Number of failed lookup of keys in the main dictionary
stats_latest_fork_usec	Number	Duration of the latest fork operation in microseconds
stats_migrate_cached_sockets	Number	The number of sockets open for MIGRATE purposes
stats_pubsub_channels	Number	Global number of pub/sub channels with client subscriptions
stats_pubsub_patterns	Number	Global number of pub/sub patterns with client subscriptions
stats_rejected_connections	Number	Number of connections rejected because of maxclients limit
stats_sync_full	Number	The number of full resyncs with replicas
stats_sync_partial_err	Number	The number of denied partial resync requests
stats_sync_partial_ok	Number	The number of accepted partial resync requests
stats_total_commands_processed	Number	Total number of commands processed by the server
stats_total_connections_received	Number	Total number of connections accepted by the server
stats_total_net_input_bytes	Bytes	The total number of bytes read from the network
stats_total_net_output_bytes	Bytes	The total number of bytes written to the network

Troubleshooting

vm.overcommit_memory is not set to 1
sysctl -w vm.overcommit_memory=1

kernel transparent_hugepage is not set to "madvise"
echo madvise > /sys/kernel/mm/transparent_hugepage/enabled

net.core.somaxconn is lower than net.ipv4.tcp_max_syn_backlog
tcp_max_syn_backlog represents the maximal number of connections in SYN_RECV queue. somaxconn represents the maximal size of ESTABLISHED queue and should be greater than tcp_max_syn_backlog, so do something like this: sysctl -w net.core.somaxconn=1024; sysctl -w net.ipv4.tcp_max_syn_backlog=512

Credits, License

• Authors: Linuxfabrik GmbH, Zurich

• License: The Unlicense, see LICENSE file.