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pmp-check-mysql-status - Check MySQL SHOW GLOBAL STATUS output.
Usage: pmp-check-mysql-status [OPTIONS] Options: -c CRIT Critical threshold. --defaults-file FILE Only read mysql options from the given file. Defaults to /etc/nagios/mysql.cnf if it exists. -C COMPARE Comparison operator to apply to -c and -w; default >=. -H HOST MySQL hostname. -I INCR Make SHOW STATUS incremental over this delay. -l USER MySQL username. -o OPERATOR The operator to apply to -x and -y. -p PASS MySQL password. -P PORT MySQL port. -S SOCKET MySQL socket file. -T TRANS Transformation to apply before comparing to -c and -w. -w WARN Warning threshold. -x VAR1 Required first status or configuration variable. -y VAR2 Optional second status or configuration variable. --help Print help and exit. --version Print version and exit. Options must be given as --option value, not --option=value or -Ovalue. Use perldoc to read embedded documentation with more details.
This Nagios plugin captures SHOW GLOBAL STATUS and SHOW GLOBAL VARIABLES from MySQL and evaluates expressions against them. The general syntax is as follows:
VAR1 [ OPERATOR VAR2 [ TRANSFORM ] ]
The result of evaluating this is compared against the -w and -c options as usual to determine whether to raise a warning or critical alert.
Note that all of the examples provided below are simply for illustrative purposes and are not supposed to be recommendations for what to monitor. You should get advice from a professional if you are not sure what you should be monitoring.
For our first example, we will raise a warning if Threads_running is 20 or over, and a critical alert if it is 40 or over:
-x Threads_running -w 20 -c 40
The threshold is implemented as greater-or-equals by default, not strictly greater-than, so a value of 20 is a warning and a value of 40 is critical. You can switch this to less-or-equals or other operators with the -C option, which accepts the arithmetic comparison operators ==, !=, >, >=, <, and <=.
You can use any variable that is present in SHOW VARIABLES or SHOW STATUS. If the variable is not found, there is an error. To warn if Threads_connected exceeds 80% of max_connections:
-x Threads_connected -o / -y max_connections -T pct -w 80
The -T option only works when you specify both -x and -y. Currently the only transformation implemented for -T is pct. The plugin uses awk to do its computations and comparisons, so you can use floating-point math; you are not restricted to integers for comparisons. Floating-point numbers are printed with six digits of precision. The -o option accepts the arithmetic operators /, *, +, and -. A division by zero results in zero, not an error.
If you specify the -I option with an integer argument, the SHOW STATUS values become incremental instead of absolute. The argument is used as a delay in seconds, and instead of capturing a single sample of SHOW STATUS and using it for computations, the plugin captures two samples at the specified interval and subtracts the second from the first. This lets you evaluate expressions over a range of time. For example, to warn when there are 10 disk-based temporary tables per second, over a 5-second sampling period:
-x Created_tmp_disk_tables -o / -y Uptime -I 5 -w 10
That is somewhat contrived, because it could also be written as follows:
-x Created_tmp_disk_tables -I 5 -w 50
The -I option has the side effect of removing any non-numeric SHOW STATUS variables. Be careful not to set the -I option too large, or Nagios will simply time the plugin out, usually after about 10 seconds.
This plugin does not support arbitrarily complex expressions, such as computing the query cache hit ratio and alerting if it is less than some percentage. If you are trying to do that, you might be doing it wrong. A dubious example for the query cache might be to alert if the hit-to-insert ratio falls below 2:1, as follows:
-x Qcache_hits -o / -y Qcache_inserts -C '<' -w 2
Some people might suggest that the following is a more useful alert for the query cache:
-x query_cache_size -c 1
To check Percona XtraDB Cluster node status you may want to use the following alert similar to what its clustercheck does:
-x wsrep_local_state -C '!=' -w 4
This plugin executes the following commands against MySQL:
This plugin executes no UNIX commands that may need special privileges.
Percona Monitoring Plugins pmp-check-mysql-status 1.0.3