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Thursday, July 31, 2008

Monitoring a website

A question we often get is: how do I monitor a website.

One has first to understand the different layers involved in a website and to what info he has access.

1. Hardware level:
A simple PING check will reveal if a server is alive or not. Monitor the response times as slower response times might indicate an error

2. OS level:
if you can then you can use the WindowsHealth or LinuxHealth check types to monitor the general health of the host running the site. This may help you to avoid situations like full dis, low memory resulting in a website failure.

3. Web server level:
A website runs on a machine, that hosts an Operating System and that has a web server. The site itself can be static or an application running as a layer on top of the web server.

A web server is typically monitored by using the TCP check to see if the server responds on the defined port (by default 80 or 443 for HTTPS)

4. Web application level:
The fastest check is to perform a HTTP HEADER check that verifies the header data sent back for a specific URL

The best option though is to use the HTTP check. It will load the given page and then scan the content to see if a predefined string is returned. If not, then an error is triggered.

You can also monitor the page download time; this is the time required to download the HTML - excluding images and any other embedded content.

Depending on your level access to your web site and server, you can define multiple layers of monitoring.

With ServersCheck you will know when your site fails before your customer(s) start calling you that there is an issue.

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