Check mysql-open-files

Overview

Reports MySQL/MariaDB’s current open-files count (Open_files, a server-wide status counter) as a percentage of open_files_limit (the per-process file-descriptor ceiling MySQL was started with). Alerts when the ratio crosses --warning / --critical. If the usage approaches the limit, the server may start refusing new connections or fail to open tables.

Important Notes:

Data Collection:

  • Queries SHOW GLOBAL VARIABLES for open_files_limit.

  • Queries SHOW GLOBAL STATUS for Open_files.

  • Calculates the percentage of open files relative to the limit.

  • Logic is taken from MySQLTuner script:mysql_stats() („Open files“ section), verified in sync with v2.8.41.

Fact Sheet

Fact

Value

Check Plugin Download

https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/mysql-open-files

Nagios/Icinga Check Name

check_mysql_open_files

Check Interval Recommendation

Every 5 minutes

Can be called without parameters

Yes

Runs on

Cross-platform

Compiled for Windows

No

3rd Party Python modules

pymysql

Help

usage: mysql-open-files [-h] [-V] [--always-ok] [-c CRITICAL]
                        [--defaults-file DEFAULTS_FILE]
                        [--defaults-group DEFAULTS_GROUP] [--timeout TIMEOUT]
                        [-w WARNING]

Reports MySQL/MariaDB's current open-files count as a percentage of
`open_files_limit` (the per-process file-descriptor ceiling MySQL was started
with; `Open_files` is a server-wide status counter, not a per-connection
metric). Alerts when the ratio crosses `--warning` / `--critical`.

options:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  --always-ok           Always returns OK.
  -c, --critical CRITICAL
                        CRIT threshold in percent. Supports Nagios ranges.
                        Default: 95
  --defaults-file DEFAULTS_FILE
                        MySQL/MariaDB cnf file to read user, host and password
                        from. Example: `--defaults-
                        file=/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)
  -w, --warning WARNING
                        WARN threshold in percent. Supports Nagios ranges.
                        Default: 85

Usage Examples

./mysql-open-files --defaults-file=/var/spool/icinga2/.my.cnf

Output (OK):

0.2% of `open_files_limit` used (80.0/32.8K).

Output (WARN / CRIT):

92.0% of `open_files_limit` used (30.2K/32.8K) [WARNING].

Recommendations:
* Raise `open_files_limit` (currently 32.8K)

States

  • WARN when Open_files / open_files_limit reaches --warning (default 85%); CRIT at --critical (default 95%).

  • --always-ok suppresses all alerts and always returns OK.

Perfdata / Metrics

Name

Type

Description

mysql_open_files

Number

Number of regular files currently opened by the server. Does not include sockets or pipes.

mysql_open_files_limit

Number

The number of file descriptors available to MySQL/MariaDB.

mysql_pct_files_open

Percentage

Open_files / open_files_limit * 100

Credits, License