I am using Nagios for our monitoring system. Recently added plugin check_url.pl to check site availability with http response codes. Plugin is working fine but it frequently reporting an invalid response code of 255. Below is the exact message displayed on dashboard and it is disappearing automatically. It looks like some attempt is failing or getting invalid response code.

SERVICE ALERT: MAINSite ;Main site URL Check;CRITICAL;SOFT;1;(Return code of 255 is out of bounds


Here is my configuration details.

Defined command like below.

define command{
command_name url_check
command_line $USER1$/check_url.pl $ARG1$
}

Here is host configuration


define host{
use linux-server ; Inherit default values from a template
host_name MAINSite ; The name we're giving to this host
alias MAINSite ; A longer name associated with the host
address abcblabla.com ; IP address of the host
check_command check_tcp!80
}

define service{
use frequent-service
host_name MAINSite
service_description Main site URL Check
check_command url_check!abcblabla.com
}


Kindly share your thoughts/experience over this.

Attached screen shot for one event.

Thanks,
Abdul

Attached Thumbnails

 

Looking at the code of the check_url.pl script, my best guess would be that you are occasionally getting a timeout (see line 23).

This is the perl script I assumed you're using.
https://exchange.nagios.org/director...ck_url/details

I'm not so impressed with that script, as you can't pass many things in as arguments. Ie - timeout, or whether it should be using --no-check-certificates for wget which its doing by default ...

I haven't used nagios in a coupld years, but I would probably use the built in check_url which would be much more widely used, and more likely more robust.

Dear fmattheus,

Thank you for the update.

Plugin is working as expected, but for some checks it is reporting invalid response code and I confirmed that those alerts are false positive.

Anybody here faced this issue? it looks like a common issue while searching in Google. but no one mentioned the fix for same.

Thanks,
Abdul

Dear Friends,

Any helping hands here?

Thanks,
Abdul

As I posted above, looking at the code, it looks like 255 means its running into a timeout.

I would, however, recommend not using that check and using the builtin 'check_url' check instead as it looks more robust, and provides better options like setting the timeout different per check.

I can not see default commend for check_url with latest version of Nagios. is it still there?
Can you please give me this plugin download page?

Apperently the main check is now called check_http ... Why look outside the core checks when there is something there already?

fmattheus,

Thanks! for your help.
Default plugin is working as expected. I changed all configs to use same.