mysqlserver add doc page

docs/20_Checks/_index.md

@@ -25,7 +25,7 @@ There is one include script used by all checks:
 * [check_haproxy_health](check_haproxy_health.md)
 * [check_haproxy_status](check_haproxy_status.md)
 * [check_memory](check_memory.md)
-* check_mysqlserver
+* [check_mysqlserver](check_mysqlserver.md)
 * check_netio
 * [check_netstat](check_netstat.md)
 * [check_onehost](check_onehost.md)

docs/20_Checks/check_mysqlserver.md

+# check Mysql / mariadb server
+
+## Introduction
+
+**check_mysqlserver** is a plugin execute different checks on a mysql server instance.
+The kind of check is defined by a parameter `-m METHOD`.
+
+## Requirements
+
+* mysql (cli tool)
+* The icinga user needs to connect to the database server (see Installation).
+
+## Syntax
+
+`$ check_mysqlserver [-i|-u|-m METHOD]`
+
+```txt
+______________________________________________________________________
+
+CHECK_MYSQLSERVER
+v1.0
+
+(c) Institute for Medical Education - University of Bern
+Licence: GNU GPL 3
+
+https://os-docs.iml.unibe.ch/icinga-checks/Checks/check_mysqlserver.html
+______________________________________________________________________
+
+USAGE:
+  check_mysqlserver [OPTIONS] -m METHOD
+
+OPTIONS:
+  -h  this help
+  -i  install monitoring user (must be executed as root)
+  -u  uninstall monitoring user (must be executed as root)
+
+PARAMETERS:
+  -m  method; valid methods are:
+      connections     current/ max connections
+      connects        connects per min and aborted connections/ clients
+      commands        current running statements insert, select, ...
+      qcache-blocks   query cache blocks total vs free
+      qcache-queries  cached / non cached queries; low memeory prunes 
+      qcache-hits     query cache efficiency: cached vs non cached and inserted
+
+EXAMPLES:
+  check_mysqlserver -i
+  check_mysqlserver -m commands
+
+```
+
+## Installation
+
+To give access to the database there is the param `-i`(for "install").
+This command needs to be run as root.
+
+```txt
+./check_mysqlserver -i
+```
+
+This creates a database user "icingamonitor" with a 64 byte random password.
+To store the credentials a file file be created: `/etc/icingaclient/.my.cnf`. It is the known mysql password file. The mysql check plugin sets $HOME to /etc/icingaclient and this config will be found automatically. 
+
+```txt
+cat /etc/icingaclient/.my.cnf
+#
+# generated on Tue Jun  8 10:01:31 CEST 2021
+#
+[client]
+user=icingamonitor
+host=localhost
+password=qrYEiPG33qNoedO4oWNrmtDOtEmQ9tw8pYEYcPbuYphUweemJEOC4fzZXIWJFvZ5
+```
+
+To test the connection run `./check_mysqlserver -m connections`. 
+
+## Checks
+
+### connections 
+
+current/ max connections
+
+```txt
+./check_mysqlserver -m connections
+OK: Mysql connections :: current/ max connections
+           max_connections:       151
+      Max_used_connections:        11
+                                  --> 7 % 
+
+        Threads_connected:         3
+                                  --> 1 % 
+
+                Questions:         1
+ 
+ |maxconnections=151;; maxusedconnections=11;; threadsconnected=3;; questions=1;;
+```
+
+### connects
+
+connects per min and aborted connections/ clients
+
+```txt
+./check_mysqlserver -m connects
+OK: Mysql connects :: connects per min and aborted connections/ clients
+               Connections:     956785 ... delta =  per min
+           Aborted_clients:         19 ... delta =  per min
+          Aborted_connects:          1 ... delta =  per min
+ 
+ |connections=0;; abortedclients=0;; abortedconnects=0;;
+```
+
+### commands
+
+current running statements insert, select, ...
+
+```txt
+./check_mysqlserver -m commands
+OK: Mysql commands :: currently executed commands
+                    delete:         0
+                    insert:         0
+                   replace:         0
+                    select:         0
+                    update:         0
+ 
+ |delete=0;; insert=0;; replace=0;; select=0;; update=0;;
+```
+
+### qcache-blocks
+
+query cache blocks total vs free
+
+```txt
+./check_mysqlserver -m qcache-blocks
+INFO: Query cache (have_query_cache) is active but query_cache_type is OFF.
+```
+
+### qcache-queries
+
+cached / non cached queries; low memeory prunes 
+
+```txt
+./check_mysqlserver -m qcache-queries
+INFO: Query cache (have_query_cache) is active but query_cache_type is OFF.
+```
+
+### qcache-hits
+
+query cache efficiency: cached vs non cached and inserted
+ 
+```txt
+./check_mysqlserver -m qcache-hits
+INFO: Query cache (have_query_cache) is active but query_cache_type is OFF.
+```
+
+
+## Uninstall
+
+As root run
+
+```txt
+./check_mysqlserver -u
+```
+
+This drops the database user `icingaclient` and removes the config file `/etc/icingaclient/.my.cnf`.