Check mysql-joins

Overview

Checks if many joins per day without indexes were executed on MySQL/MariaDB. 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-joins

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

Checks if many joins per day without indexes were executed on 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-joins --hostname localhost --username root --password mypassword

Output:

3909 joins performed without indexes [WARNING]. Set join_buffer_size > 4194304, or always use indexes with JOINs. Raise the join_buffer_size until JOINs not using indexes are found.

States

  • WARN if there are more than 250 joins without indexes per day.

Perfdata / Metrics

Name

Type

Description

mysql_join_buffer_size

Bytes

Minimum size in bytes of the buffer used for queries that cannot use an index, and instead perform a full table scan. Increase to get faster full joins when adding indexes is not possible, although be aware of memory issues, since joins will always allocate the minimum size.

mysql_select_full_join

Continous Counter

Number of joins which did not use an index. If not zero, you may need to check table indexes.

mysql_select_range_check

Continous Counter

Number of joins without keys that check for key usage after each row. If not zero, you may need to check table indexes.

mysql_uptime

Seconds

Number of seconds the server has been running.

mysql_joins_without_indexes

Continous Counter

Select_range_check + Select_full_join

mysql_joins_without_indexes_per_day

Number

joins_without_indexes / Uptime in days

Credits, License