Sam Pointer

There is a nasty bug in the Nagios check_http plugin before version 1.4.14 whereby the leading slash (/) of the URI paramter is left off of the string when encountering a 301 or 302 redirect. This can lead to errors such as:

HTTP WARNING - redirection creates an infinite loop

or others regarding HTTP redirection that is more than 15 levels deep (if you compiled with the default value). From the changelog:

2008-09-01  Holger Weiss 

* plugins/check_http.c: Under some circumstances, the 'url' path of
a redirection target missed a leading slash.  While this was fixed
later on, the incomplete 'url' was used for redirection loop
detection and error messages.  This is now fixed by adding the
missing slash immediately.  git-svn-id:

https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/trunk@2049 f882894a-f735-0410-b71e-b25c423dba1c

Here is the full changelog.

I recently tried out Nic le Roux’s sched_downtime Perl script as a quick punt to getting recurring Nagios downtime working. Cool script, and it beats having to hand-roll something to append the the nagios.cmd command pipe file by hand. Why reinvent the wheel, right?

There’s a small problem with the script, on my 3.0.6 install of Nagios anyway, whereby the command string that is produced is missing a field, leading to the commands not being acted upon. See:

[1264767246] EXTERNAL COMMAND: SCHEDULE_SVC_DOWNTIME;sam;ssh;1264767600;1264768200;1;600;Sam;Testing service recurring scheduled downtime
[1264771220] EXTERNAL COMMAND: SCHEDULE_SVC_DOWNTIME;sam;ssh;1264771800;1264772400;1;0;600;Sam;Testing service recurring scheduled downtime

See the extra field there? The same is true of host scheduled downtime too. If we check the documentation we can see that the extra field is a ‘trigger_id’.

I’ve created a patch that will enable you to use the script against Nagios versions that expect the 3.x format command strings. My patch deals with the possibility of being able to trigger downtime based on other downtime events by conveniently ignoring it, and hardcoding a zero in that field. I didn’t need it, sorry!