Monitoring URLs with Nagios

Question

I'm trying to monitor actual URLs, and not only hosts, with Nagios, as I operate a shared server with several websites, and I don't think its enough just to monitor the basic HTTP service (I'm including at the very bottom of this question a small explanation of what I'm envisioning).

(Side note: please note that I have Nagios installed and running inside a chroot on a CentOS system. I built nagios from source, and have used yum to install into this root all dependencies needed, etc...)

---

I first found check_url, but after installing it into /usr/lib/nagios/libexec, I kept getting a "return code of 255 is out of bounds" error. That's when I decided to start writing this question (but wait! There's another plugin I decided to try first!)

After reviewing This Question that had almost practically the same problem I'm having with check_url, I decided to open up a new question on the subject because a) I'm not using NRPE with this check b) I tried the suggestions made on the earlier question to which I linked, but none of them worked. For example...

./check_url some-domain.com | echo $0

returns "0" (which indicates the check was successful)

I then followed the debugging instructions on Nagios Support to create a temp file called debug_check_url, and put the following in it (to then be called by my command definition):

#!/bin/sh
echo `date` >> /tmp/debug_check_url_plugin
echo $*  /tmp/debug_check_url_plugin
/usr/local/nagios/libexec/check_url $*

Assuming I'm not in "debugging mode", my command definition for running check_url is as follows (inside command.cfg):

'check_url' command definition
define command{
       command_name    check_url
       command_line    $USER1$/check_url $url$
}

(Incidentally, you can also view what I was using in my service config file at the very bottom of this question)

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Before publishing this question, however, I decided to give 1 more shot at figuring out a solution. I found the check_url_status plugin, and decided to give that one a shot. To do that, here's what I did:

1. mkdir /usr/lib/nagios/libexec/check_url_status/
2. downloaded both check_url_status and utils.pm
3. Per the user comment / review on the check_url_status plugin page, I changed "lib" to the proper directory of /usr/lib/nagios/libexec/.

4. Run the following:

   ./check_user_status -U some-domain.com. When I run the above command, I kept getting the following error:

bash-4.1# ./check_url_status -U mydomain.com Can't locate utils.pm in @INC (@INC contains: /usr/lib/nagios/libexec/ /usr/local/lib/perl5 /usr/local/share/perl5 /usr/lib/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib/perl5 /usr/share/perl5) at ./check_url_status line 34. BEGIN failed--compilation aborted at ./check_url_status line 34.

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So at this point, I give up, and have a couple of questions:

1. Which of these two plugins would you recommend? check_url or check_url_status? (After reading the description of check_url_status, I feel that this one might be the better choice. Your thoughts?)
2. Now, how would I fix my problem with whichever plugin you recommended?

---

At the beginning of this question, I mentioned I would include a small explanation of what I'm envisioning. I have a file called services.cfg which is where I have all of my service definitions located (imagine that!).

The following is a snippet of my service definition file, which I wrote to use check_url (because at that time, I thought everything worked). I'll build a service for each URL I want to monitor:

###
# Monitoring Individual URLs...
#
###
define service{
        host_name                       {my-shared-web-server}
        service_description             URL: somedomain.com
        check_command                   check_url!somedomain.com
        max_check_attempts              5
        check_interval                  3
        retry_interval                  1
        check_period                    24x7
        notification_interval           30
        notification_period             workhours
}

Answer 1

I was making things WAY too complicated.

The built-in / installed by default plugin, check_http, can accomplish what I wanted and more. Here's how I have accomplished this:

My Service Definition:

  define service{
            host_name                       myers
            service_description             URL: my-url.com
            check_command                   check_http_url!http://my-url.com
            max_check_attempts              5
            check_interval                  3
            retry_interval                  1
            check_period                    24x7
            notification_interval           30
            notification_period             workhours
    }

My Command Definition:

define command{
        command_name    check_http_url
        command_line    $USER1$/check_http -I $HOSTADDRESS$ -u $ARG1$
}