Customer asked:
What is the need for ModJK? Also, does it have performance penalties?
Answer:
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The purpose of ModJK is to forward requests from the web server to the application server. Especially this is needed if you integrated Identity Manager with Site Minder. In that situation you have SiteMinder protecting IDM with the SiteMinder web agent that's installed into the web server. Once the protection is good the request need to get to the application server where the IDM application is. This is what the ModJK does, it will route the requests to the application server. Further, you can configure load balancing on the modJK configuration and toggle between a cluster of application servers so that you route these requests to all of them in round robin fashion.
ModJK is a 3rd party product and allows you to specify round robin policy if you need to route the requests to a cluster of application servers. Also, you should configure a filter that will ensure that only requests for IDM (/iam/im*) will be forwarded to the app server for IDM. This is so that no other unrelated traffic will take place. ModJK does not have a performance penalty and we have never learned of one and I wouldn't say performance is a consideration.
Yours,
Sagi Gabay,
CA Technologies.