On a Windows server, a service was hanging and nobody noticed it. The application team found out that this service, when working correctly, always creates certain temporary folders which disappear after a few minutes. This can be monitored, of course!
As the Windows servers have NSClient installed, I can use check_nrpe from the Icinga server to check for the folders. So I created a folder "claudiotest" in the temp folder of the application:
Note that I used an asterisk wildcard in the path in order to simulate the temporary folders of the application, they all start with the same name but have a different ending.
$ /usr/lib/nagios/plugins/check_nrpe -H windowsserver -c check_files -a "file=C:\Program Files\Application\tmp\claudio*"
OK: All 1 files are ok|
Indeed, there was one file found (my folder "claudiotest").
What if I search for another name?
$ /usr/lib/nagios/plugins/check_nrpe -H windowsserver -c check_files -a "file=C:\Program Files\Application\tmp\claudiooo*"
No files found|
No surprise, nothing was found with that name.
So here I had to add filters to limit my search result. I only wanted to have results matching the filename (C:\Program Files\Application\tmp\claudio*) and an age older than 15 minutes:
$ /usr/lib/nagios/plugins/check_nrpe -H windowsserver -c check_files -a "file=C:\Program Files\Application\tmp\claudio*" "filter=age>900"
OK: All 1 files are ok|
So far so good, but it should not be OK, it should WARN that the application is probably hanging. For this the "warn" argument must be used:
$ /usr/lib/nagios/plugins/check_nrpe -H windowsserver -c check_files -a "file=C:\Program Files\Application\tmp\claudio*" "filter=age>900" "warn=count>0"
WARNING: 1/1 files (claudiotest)|'count'=1;0;0
This means: As soon as the check found at least one file matching the filename and the age is older than 15min, it will return a warning.
But I faced one more issue. When no such directories exist (which can happen), I got an UNKNOWN return code (3):
$ /usr/lib/nagios/plugins/check_nrpe -H windowsserver -c check_files -a "file=C:\Program Files\Application\tmp\claudiooo*" "filter=age>900" "warn=count>0"; echo $?
No files found|'count'=0;0;0
3
This means, that in Icinga this would be shown as an UNKNOWN alert, which should not be the case. But this can be solved with the parameter "empty-state". This basically means when nothing applies to the filter (no result), this return code should be used:
$ /usr/lib/nagios/plugins/check_nrpe -H windowsserver -c check_files -a "file=C:\Program Files\Application\tmp\claudiooo*" "filter=age>900" "empty-state=ok" "warn=count>0"; echo $?
No files found|'count'=0;0;0
0
This time, the return code was OK (0).
And the final check:
$ /usr/lib/nagios/plugins/check_nrpe -H windowsserver -c check_files -a "file=C:\Program Files\Application\tmp\claudio*" "filter=age>900" "empty-state=ok" "warn=count>0"
WARNING: 1/1 files (claudiotest)|'count'=1;0;0
Solved!
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