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HTTP Monitor and multiple web server farm

Hi,

I have a scenario where I am trying to monitor multiple web servers that host the same web site.

We distribute requests to each web server in the farm via a hardware load balancer, which can detect if one of the destination sites is down, however we need a detection mechanism that alerts our operators also. I would like to have APM poll each server for each site hosted, and alert us if a site is down on any of our HTTP servers. We host multiple sites off the same port, so detecting if there is a site listening on a particular port is not enough.

The current functionality in the HTTP monitor seems to result in APM polling our load balanced IP (the one dns resolves to) for each site, instead of the web server that the monitor is assigned to. Thus, if a server goes down, APM never sees it as our load balancer stops sending requests there.

Short of writing a custom script, is there a way to get one of the built in HTTP or TCP monitors to poll the health of the site on each server in the farm? It would need to connect to port 80 on that machine, and then send an HTTP GET for the particular URL to monitor...

If that is not possible, is there a script out there that already does this?

Any help would be appreciated.

James.

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load_balancer

Accepted answers

All comments

josh.clark

Add each server in your web farm as a node in Orion. Then assign the HTTP Monitor to each of these nodes. Just ignore the load balancer.

jameswyld

I have it assigned to each node, however it does not seem to be working quite this way. I want to poll for the existence of http://www.url.com on port 80 on node 10.x.x.x

Component Type: HTTP Monitor

Credential: None

Port: 80

URL: http://www.url.com/debug.asp

Proxy: none

When I set this to test against a server which I have manually offlined (it does not respond on that http address, and this has been verified locally on that machine), the HTTP Monitor is up. If I manually set the host file on the solarwinds machine for www.url.com to point to the specific server I am testing, then the HTTP Monitor is down.

This indicates to me that it is trying to resolve the url, rather than ask the node it is assigned to serve that url. Is there a setting I am missing?

Edit: Just to confirm, I have indeed set up each server as a separate node in Orion.

josh.clark

You can use a URL of http://${IP}/debug.asp

The variable ${IP} will be replaced with the IP Address of that node.

jameswyld

You can use a URL of http://${IP}/debug.asp

The variable ${IP} will be replaced with the IP Address of that node.

This does not achieve the goal unfortunately as there are multiple sites on each IP, with the webserver using host headers to differentiate which site to serve. The monitor I'm looking for needs to open the connection to the nodes IP address on port 80 (eg: ${IP}:${PORT}) and then send it an HTTP Request for www.url.com.

josh.clark

You can use a URL of http://${IP}/debug.asp

The variable ${IP} will be replaced with the IP Address of that node.

I just noticed that you are using host headers, so this will probably not work. The method I suggested would connect using a URL of http://1.2.3.4/debug.asp. If you have your servers configured to return different websites based on the hostname an IP address will cause issues.

What you need is the ability to specify the host header so that your IIS instance can determine which website it should let process the URL. We don't have that ability in the HTTP monitor currently. I'll open a feature request for this. I can't think of another way to get this to work without using scripts.