Check mysql-binlog-cache

Overview

Checks if a certain amount of transactions used a temporary disk cache because they could not fit in the regular binary log cache in MySQL/MariaDB. Logic is taken from MySQLTuner script:mysql_stats(), v1.9.8.

Hints:

  • If log_bin is set to OFF, this check makes no sense.

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

Checks if a certain amount of transactions used a temporary disk cache because
they could not fit in the regular binary log cache 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-binlog-cache --hostname localhost --username root --password mypassword

Output:

0% binlog cache memory access (0 memory / 0 total).

States

  • WARN if more than 10% of all transactions using the binary log cache are read from disk.

Perfdata / Metrics

Name

Type

Description

mysql_binlog_cache_disk_use

Continous Counter

Number of transactions which used a temporary disk cache because they could not fit in the regular binary log cache, being larger than binlog_cache_size.

mysql_binlog_cache_size

Bytes

If the binary log is active, this variable determines the size in bytes, per-connection, of the cache holding a record of binary log changes during a transaction.

mysql_binlog_cache_use

Continous Counter

Number of transaction which used the regular binary log cache, being smaller than binlog_cache_size.

mysql_pct_binlog_cache

Percentage

(Binlog_cache_use - Binlog_cache_disk_use) / Binlog_cache_use * 100

Credits, License