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mysql-memory

README.rst

Check mysql-memory

Overview

Checks current and maximum possible memory usage specifically for MySQL/MariaDB. Logic is taken from MySQLTuner script:mysql_stats(), v1.9.8.

Hints:

Fact Sheet

Check Plugin Download https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/mysql-memory
Check Interval Recommendation Every 5 minutes
Can be called without parameters Yes
Compiled for Linux, Windows
Requirements User with PROCESS 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.
3rd Party Python modules psutil, pymysql

Help

usage: mysql-memory [-h] [-V] [--always-ok] [--defaults-file DEFAULTS_FILE]
                    [--defaults-group DEFAULTS_GROUP] [--timeout TIMEOUT]

Checks memory metrics for 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.
  --defaults-file DEFAULTS_FILE
                        Specifies a cnf file to read parameters like user,
                        host and password from (instead of specifying them on
                        the command line), for example
                        `/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)

Usage Examples

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

Output:

67.6% - total: 31.3GiB, used: 21.1GiB. Maximum possible memory usage is 99.5% (possible peak: 31.1GiB). Reduce your overall MySQL memory footprint for system stability. Overall possible memory usage with other processes will exceed memory . Dedicate this server to your database for highest performance.

Calculations:
* Memory usage according to Performance Schema: pfm = 0.0B
* Server Buffers: sb = 18.3GiB
* Max. Total per Thread Buffers: mtptb = 2.8GiB
* Total per Thread Buffers: tptb = 12.8GiB
* Max. Used Memory: mum = sb + mtptb + pfm = 18.3GiB + 2.8GiB + 0.0B = 21.1GiB
* Possible Peak Memory: ppm = sb + tptb + pfm = 18.3GiB + 12.8GiB + 0.0B = 31.1GiB
* Physical Memory: pm = 31.3GiB
* Max Used Memory %: mump = mum / pm * 100 = 21.1GiB / 31.3GiB * 100 = 67.6B%
* Max Possible Memory Usage %: mpmu = ppm / pm * 100 = 31.1GiB / 31.3GiB * 100 = 99.5B%

States

  • WARN if max_used_memory > 2 GB on 32 bit systems.
  • WARN if max_used_memory > 85%.
  • WARN if physical_memory < max_peak_memory + memory usage by other processes (except some specific like MySQL/MariaDB or Systemd).

Perfdata / Metrics

Name Type Description
mysql_aria_pagecache_buffer_size Bytes The size of the buffer used for index and data blocks for Aria tables. This can include explicit Aria tables, system tables, and temporary tables.
mysql_innodb_buffer_pool_size Bytes InnoDB buffer pool size in bytes. The primary value to adjust on a database server with entirely/primarily InnoDB tables, can be set up to 80% of the total memory in these environments.
mysql_innodb_log_buffer_size Bytes Size in bytes of the buffer for writing InnoDB redo log files to disk. Increasing this means larger transactions can run without needing to perform disk I/O before committing.
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.
mysql_key_buffer_size Bytes Size of the buffer for the index blocks used by MyISAM tables and shared for all threads.
mysql_max_allowed_packet Bytes Maximum size in bytes of a packet or a generated/intermediate string. The packet message buffer is initialized with the value from net_buffer_length, but can grow up to max_allowed_packet bytes.
mysql_max_connections Number The maximum number of simultaneous client connections.
mysql_max_heap_table_size Bytes Maximum size in bytes for user-created MEMORY tables.
mysql_max_peak_memory Bytes server_buffers + total_per_thread_buffers + performance schema usage
mysql_max_tmp_table_size Bytes max(max_heap_table_size, tmp_table_size)
mysql_max_total_per_thread_buffers Bytes per_thread_buffers * max_used_connections
mysql_max_used_connections Number Max number of connections ever open at the same time. The global value can be flushed by FLUSH STATUS.
mysql_max_used_memory Bytes server_buffers + max_total_per_thread_buffers + performance schema usage
mysql_pct_max_physical_memory Percentage max_peak_memory / physical_memory * 100
mysql_pct_max_used_memory Percentage max_used_memory / physical_memory * 100
mysql_per_thread_buffers Bytes Have a look at the source code.
mysql_physical_memory Bytes Total physical memory (exclusive swap).
mysql_query_cache_size Bytes Size in bytes available to the query cache. About 40KB is needed for query cache structures, so setting a size lower than this will result in a warning.
mysql_read_buffer_size Bytes Each thread performing a sequential scan (for MyISAM, Aria and MERGE tables) allocates a buffer of this size in bytes for each table scanned.
mysql_read_rnd_buffer_size Bytes Size in bytes of the buffer used when reading rows from a MyISAM table in sorted order after a key sort.
mysql_server_buffers Bytes Have a look at the source code.
mysql_sort_buffer_size Bytes Each session performing a sort allocates a buffer with this amount of memory. Not specific to any storage engine.
mysql_thread_stack Bytes Stack size for each thread.
mysql_tmp_table_size Bytes The largest size for temporary tables in memory (not MEMORY tables) although if max_heap_table_size is smaller the lower limit will apply.
mysql_total_per_thread_buffers Bytes per_thread_buffers * max_connections

Troubleshooting

Overall possible memory usage with other process will exceed memory [WARNING]. Dedicate this server to your database for highest performance.
Decrease max_connections, tune buffer settings, stop other processes or increase memory.

Credits, License