Session Oddities

One of the clients we host complained about losing their session. Blackboard recommended we switch how our load balancer is handling the session persistence. Before agreeing to do that, we decided to use Blackboard’s script to determine if there is a problem before trying to fix something which may or may not exist.

An acceptable number of sessions showing on multiple nodes of a cluster is less than 5%. When I ran the test, I found 35.8% matched this criteria. But wait just a second, this seemed like an extraordinarily high number. I ran a second test for an identically configured cluster on the same hardware to find only 4.3%. Why are these so different?

Most cases of this “duplicated session” I spot checked were 1 hit for autosignon on another node. Blackboard confirmed these happen before the user has logged in, so they could appear on the other node. So I ran the test again ignoring these autosignon requests and found we were down to 7.2%. Close to acceptable but not quite.

 Similar to autosignon, the editonpro.js appeared in the majority of the cases I spot checked as the sole hit another node. Once, I removed those from the test, I was down to 0.7%. My control cluster was down to 1.4%. 

One would hope the the script used to determine the amount of duplicate sessions would ignore or remove from the data set the known false positive log entries. 

One would also hope the script instructions (requires login to Blackboard help site) would help users account for these false positives. I did leave a comment on the instructions to hopefully help the next person who has to do this.

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