Check mysql-system

Overview

Checks Linux kernel parameters that affect MySQL/MariaDB stability and performance: vm.swappiness, the asynchronous-I/O event ceiling fs.aio-max-nr, the per-process file-handle ceiling fs.nr_open, and (on hosts that mount NFS) the sunrpc TCP slot-table size. Optionally also flags hosts that listen on too many TCP ports. Logic is taken from MySQLTuner:get_kernel_info() and has been verified in sync with MySQLTuner.

Important Notes:

  • Must be running locally on the MySQL/MariaDB server to check the system requirements

  • See additional notes for all mysql monitoring plugins

  • Unlike MySQLTuner, this plugin does not check if all processes other than MySQL/MariaDB use more than 15% of total system memory. You may intentionally run a small DB on an application server, or the DB may not need 85% of available RAM.

Data Collection:

  • Counts distinct local TCP ports in LISTEN state via psutil (if available). Connections in ESTABLISHED, TIME_WAIT etc. are not counted

  • Reads Linux kernel parameters via sysctl

  • Does not need access to MySQL/MariaDB itself

Fact Sheet

Fact

Value

Check Plugin Download

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

Nagios/Icinga Check Name

check_mysql_system

Check Interval Recommendation

Every 5 minutes

Can be called without parameters

Yes

Runs on

Linux

Compiled for Windows

No

Requirements

Read access to /proc/sys/* (default for any user). No MySQL/MariaDB credentials needed - the plugin does not connect to the database

3rd Party Python modules

psutil

Help

usage: mysql-system [-h] [-V] [--always-ok]
                    [--maxportsallowed MAXPORTSALLOWED]

Checks Linux kernel parameters that affect MySQL/MariaDB stability and
performance: `vm.swappiness`, the asynchronous-I/O event ceiling `fs.aio-max-
nr`, the per-process file-handle ceiling `fs.nr_open`, and (on hosts that
mount NFS) the sunrpc TCP slot-table size (`sunrpc.tcp_slot_table_entries`).
Optionally also flags hosts that listen on too many TCP ports. Alerts on
misconfigured settings.

options:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  --always-ok           Always returns OK.
  --maxportsallowed MAXPORTSALLOWED
                        Maximum number of TCP ports listening on this host. 0
                        disables the check. Default: 0

Usage Examples

./mysql-system --maxportsallowed 15

Output:

56 listening TCP ports system-wide, exceeds `--maxportsallowed` limit of 15. Consider dedicating a server for your database installation with less services running on. `vm.swappiness` is 60, should be <= 10 (`echo 10 > /proc/sys/vm/swappiness`, or `vm.swappiness=10` in /etc/sysctl.conf for persistence). `sunrpc.tcp_slot_table_entries` is 2, should be > 100 (recommended: 128; `echo 128 > /proc/sys/sunrpc/tcp_slot_table_entries`, or `sunrpc.tcp_slot_table_entries=128` in /etc/sysctl.conf for persistence). `fs.aio-max-nr` is 1048576 (1.0M). `fs.nr_open` is 2147483584 (2.1G).

When the host is fully tuned, the OK output enumerates each verified setting. Large counters are also rendered with an SI suffix in parens:

16 listening TCP ports system-wide. `vm.swappiness` is 5. `sunrpc.tcp_slot_table_entries` is 128. `fs.aio-max-nr` is 1048576 (1.0M). `fs.nr_open` is 1073741816 (1.1G).

States

  • OK if all kernel parameters are within the recommended range and the port count is acceptable.

  • WARN if --maxportsallowed is set and the count of listening TCP ports exceeds it.

  • WARN if vm.swappiness > 10.

  • WARN if sunrpc.tcp_slot_table_entries <= 100 (only on hosts where /proc/sys/sunrpc exists).

  • WARN if fs.aio-max-nr < 1M.

  • WARN if fs.nr_open < 1M.

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

Perfdata / Metrics

Name

Type

Description

mysql_kernel_fs_aio_max_nr

Number

Maximum number of asynchronous I/O operations the system can handle.

mysql_kernel_fs_nr_open

Number

Per-process ceiling for the number of open file descriptors.

mysql_kernel_sunrpc_tcp_slot_table_entries

Number

Number of TCP RPC entries pre-allocated for in-flight RPC requests. Only emitted when /proc/sys/sunrpc exists.

mysql_kernel_vm_swappiness

Percentage

Balance between swapping out runtime memory versus dropping pages from the system page cache.

mysql_listening_ports

Number

Count of distinct local TCP ports in LISTEN state.

Credits, License