check_systemd_unit

                                

        
        

            
            

                

    

    
About


The check plugin check_systemd_unit monitors a systemd unit.


Usage


The plug-and-play Linux binaries
take the following CLI arguments and no environment variables:


$ ./check_systemd_unit -unit UNIT \
[-warn PROPERTY(THRESHOLD) ...] [-crit PROPERTY(THRESHOLD) ...] \
[-js-warn JS_EXPR ...] [-js-crit JS_EXPR ...]


UNIT is the systemd unit to monitor, e.g. icinga2.service.


PROPERTY(THRESHOLD) specifies a numeric unit property and
an alert threshold range conforming to the Nagio$ check plugin API,
e.g. -warn NRestarts(@~:42) warns if the unit's NRestarts are <= 42.


JS_EXPR is an alert condition written in JavaScript,
e.g. -js-crit ActiveState==="active" returns status critical
if the unit's ActiveState is not "active".


Legal info


To print the legal info, execute the plugin in a terminal:


$ ./check_systemd_unit


In this case the program will always terminate with exit status 3 ("unknown")
without actually checking anything.


Testing


If you want to actually execute a check inside a terminal,
you have to connect the standard output of the plugin to anything
other than a terminal – e.g. the standard input of another process:


$ ./check_systemd_unit -unit icinga2.service |cat


In this case the exit code is likely to be the cat's one.
This can be worked around like this:


bash $ set -o pipefail
bash $ ./check_systemd_unit -unit icinga2.service |cat


Actual monitoring


Just integrate the plugin into the monitoring tool of your choice
like any other check plugin. (Consult that tool's manual on how to do that.)
It should work with any monitoring tool
supporting the Nagio$ check plugin API.


The only limitation: check_systemd_unit must be run on the host
to be checked – either with an agent of your monitoring tool or by SSH.
Otherwise it will check the host your monitoring tool runs on.


Icinga 2


This repository ships the check command definition
as well as a service template and host example for Icinga 2.


The service definition will work in both correctly set up Icinga 2 clusters
and Icinga 2 instances not being part of any cluster
as long as the hosts are named after the endpoints.