Check mysql-table-cache

Overview

Checks the hit rate for open tables cache lookups in MySQL/MariaDB. Logic is taken from MySQLTuner script:mysql_stats(), v1.9.8.

Hints:

• See additional notes for all mysql monitoring plugins
• Requires MySQL/MariaDB v5.1+.

Fact Sheet

Check Plugin Download	https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/mysql-table-cache
Check Interval Recommendation	Every 5 minutes
Can be called without parameters	Yes
Compiled for	Linux, Windows
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-table-cache [-h] [-V] [--always-ok]
                         [--defaults-file DEFAULTS_FILE]
                         [--defaults-group DEFAULTS_GROUP] [--timeout TIMEOUT]

Checks the hit rate for open tables cache lookups in MySQL/MariaDB.

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

Output:

100.0% table cache hit rate (2.3M hits / 2.3M requests)

States

• WARN if table_cache_hit_rate < 20%

Perfdata / Metrics

Name	Type	Description
mysql_open_files_limit	Number	The number of file descriptors available to MariaDB.
mysql_open_tables	Number	Number of currently opened tables, excluding temporary tables.
mysql_opened_tables	Continous Counter	Number of tables the server has opened.
mysql_table_cache_hit_rate	Percentage	Table_open_cache_hits / (Table_open_cache_hits + Table_open_cache_misses) * 100. If Table_open_cache_hits is not available: Open_tables / Opened_tables * 100
mysql_table_open_cache	Number	Maximum number of open tables cached in one table cache instance.
mysql_table_open_cache_hits	Continous Counter	Number of hits for open tables cache lookups.
mysql_table_open_cache_misses	Continous Counter	Number of misses for open tables cache lookups.

Credits, License

• Authors: Linuxfabrik GmbH, Zurich

• License: The Unlicense, see LICENSE file.

• Credits:

  • heavily inspired by MySQLTuner (https://github.com/major/MySQLTuner-perl)