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Check mysql-thread-cache

Overview

MySQL/MariaDB tracks the number of threads it caches for re-use. This plug-in checks the cache hit rate after a minimum uptime of one hour. If the thread pool is active, thread_cache_size is ignored. Logic is taken from MySQLTuner script:mysql_stats(), v1.9.8.

Hints:

Fact Sheet

Fact Value
Check Plugin Download https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/mysql-thread-cache
Check Interval Recommendation Once an hour
Can be called without parameters Yes
Compiled for Windows No
Requirements User with no privileges, locked down to 127.0.0.1 - for example monitoring\@127.0.0.1. Usernames in MySQL/MariaDB are limited to 16 chars in specific versions.
3rd Party Python modules pymysql

Help

usage: mysql-thread-cache [-h] [-V] [--always-ok]
                          [--defaults-file DEFAULTS_FILE]
                          [--defaults-group DEFAULTS_GROUP]
                          [--timeout TIMEOUT]

Checks the number of threads MySQL/MariaDB caches for re-use.

options:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  --always-ok           Always returns OK.
  --defaults-file DEFAULTS_FILE
                        Specifies a cnf file to read parameters like user,
                        host and password from (instead of specifying them on
                        the command line), for example
                        `/var/spool/icinga2/.my.cnf`. Default:
                        /var/spool/icinga2/.my.cnf
  --defaults-group DEFAULTS_GROUP
                        Group/section to read from in the cnf file. Default:
                        client
  --timeout TIMEOUT     Network timeout in seconds. Default: 3 (seconds)

Usage Examples

./mysql-thread-cache --defaults-file=/var/spool/icinga2/.my.cnf

Output:

100.0% thread cache hit rate (910.0 threads created / 8.7M connections).

States

  • WARN if thread_cache_size is 0.
  • WARN if thread cache hit rate is \<= 50%.

Perfdata / Metrics

Name Type Description
mysql_connections Continous Counter Number of connection attempts (both successful and unsuccessful).
mysql_thread_cache_hit_rate Percentage 100 - Threads_created / Connections * 100
mysql_thread_cache_size Bytes Number of threads server caches for re-use.
mysql_threads_created Continous Counter Number of threads created to respond to client connections. If too large, look at increasing thread_cache_size.

Credits, License