Fun with Web Metrics

What's going on?

Session IDs: I – Why and Where

One of the things that we changed a while back that has made our lives easier was to tag every visit to the site with a session ID.   Basically, if the session cookie doesn’t exist, one is created, and the cookie’s expiration time is reset with each page load, unless it times out (30 minutes for our sites).

The data stored is just the IP of the client and the UNIX time stamp of the cookie’s creation, e.g.:

Then we append this to each line of the HTTP server log as an extra field.

In doing so, it makes it very straightforward to pull out individual sessions for analysis.  It also gets around some of the problems you have with IP overlapping from routers.   For example if you are trying to look at classroom usage of a resource, and all the traffic is logged as coming from the same IP, it’s not really possible to tell how many concurrent sessions there are, nor what the traffic pattern is.   Because the session ID is stored by each client, unless (in this case) two sessions begin at the same time, they’ll still have separate IDs.



November 29, 2010 - Posted by | sessions |

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