checking for http response headers

[moses.moore]

I've been asked to monitor a web url to make sure the 'Location:' http header is correct, and alert if it changes.

I don't know how to do this in Zabbix. I can make a web check step that fetches only headers, or a webcheck step that sends custom http request headers, or a web check step that searches the http response body for a substring... but I don't know how to write a web check step that searches the http response headers for a substring.

Is there something I'm overlooking when reading the manual?

[jamesNJ]

I don't see that there is a trivial way to check the headers with a web scenario, however probably the scenario was not really designed to do that.

If all you are interested in is a basic check of a page for a particular header, you could write a script and use UserParameter to invoke your scrip with the URL and have it return the header of interest. Then your trigger would check for the desired string.

If invoking a script from zabbix is undesirable, you could also write a very simple cron job which dumps the page headers to a file, and then use the zabbix agent (like log monitoring) to look for a particular string.

curl can dump just the headers of a url using -I option

I hope that helps

[moses.moore]

Yeah I can easily write

curl -s |grep "Location: http://blah" >/dev/null \
  || mail sysdamin@company <<<"Problem with website xyz"

... but then I'm discarding Zabbix for something handcrafted, and it makes the people I work for wonder why I deployed Zabbix.

The webcheck stuff is already weird; I have to associate each webcheck with a Host-object, but the Host-object may not be the same as the host where the website lives; especially in cases where I must watch a machine I can't install a Zabbix agent into. It's really weird getting an alert that says "Host saturn webcheck failed" when I know the website is actually hosted on host mars.

I was hoping there was a Zabbix-y way, instead of bolting some other monitoring system onto the side of a Zabbix agentd. Is there a better way?

[jamesNJ]

Well, I somewhat agree that the Item association with hosts takes some thought. I think maybe "applications" were meant to help there but I haven't used that yet.

Zabbix won't accommodate every single thing so some customization is usually needed.

I wasn't suggesting to set up a completely separate monitor via e-mail, but was suggesting you can write a script that pulls that data into zabbix and then use the zabbix system to poll for status, trigger, action/alert/etc.

I like UserParameter, but it looks like your need might be simple enough for system.run, try something like this:

system.run["curl -Is http://192.168.1.1 | fgrep Location"]

Curl will just dump the headers and fgrep will filter on Location. Pull that in as s string to Zabbix. Once you have it in the system as a periodic poll, you can write a trigger to check the location. You could hard-code this, or set a per-host macro, or set up another zabbix item which pulls in the desired location and compare against it.

I hope this helps.