Check mysql-thread-cache

Overview

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

Hints:

  • On RHEL 7+, one way to install the Python MySQL Connector is via pip install pymysql

  • Compared to check_mysql / MySQLTuner this check currently:

    • supports only simple login with username/password (not via SSL/TLS)

    • does not support a connection via socket

Fact Sheet

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

Available for

Python 3, Windows

Requirements

Python module pymysql; 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.

Help

usage: mysql-thread-cache [-h] [-V] [--always-ok] [-H HOSTNAME] [-p PASSWORD]
                          [--port PORT] [-u USERNAME]

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.
  -H HOSTNAME, --hostname HOSTNAME
                        MySQL/MariaDB hostname. Default: 127.0.0.1
  -p PASSWORD, --password PASSWORD
                        Use the indicated password to authenticate the
                        connection. Default:
  --port PORT           MySQL/MariaDB port. Default: 3306
  -u USERNAME, --username USERNAME
                        MySQL/MariaDB username. Default: root

Usage Examples

./mysql-thread-cache --hostname localhost --username root --password mypassword

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