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:

  • Requires MySQL/MariaDB v5.1+.

  • 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-table-cache

Check Interval Recommendation

Every 5 minutes

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-table-cache [-h] [-V] [--always-ok] [-H HOSTNAME] [-p PASSWORD]
                         [--port PORT] [-u USERNAME]

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.
  -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-table-cache --hostname localhost --username root --password mypassword

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