Replacing the WebSphere Apache Plugin with iRules

Our company is new to F5 and last April we started a project to use the F5 instead of the plugin. It took me two months to figure out all of this stuff and basically what you have it was I did. Of course since we were new to the F5, I had to learn how to do things on the F5 and learn iRules (I had never seen TCL before). I'm glad to see that what I did was the right way to do it.

 

 

One point though. There is a problem with using the iRule to use the JSESSION cookie for session persistence in the case where you have multiple pools. An fairly easy modification to that iRule is instead of using the full cookie as the persist key is to only use the 1st 26 positions, all the way up to the ":".

 

 

The issue is that the cookie has the jessionid that is unique to this session and then a unique identifier is added to the end for each WebSphere server you end up using. With two pools you have two servers. So as you get switched to another server the cookie value changes.

 

 

We have four pools, so you could get sent to four different servers. Each server tags the end of the JSESSION cookie with their unique id and thus the cookie value gets changed.

 

 

This all assumes that the WebSphere Servers are setup to share the JSESSION cookie. If they are not, then you get into real trouble.