Hi Sunu,
Quick look at your script, tells that you are using c$http$cluster_client_ip,
but http record doesn’t have any field name “cluster_client_ip”.
I think what you want is c$id$orig_ip as the client ip, if that’s what the purpose of cluster_client_ip is.
Also, a great resource to test out your scripts is try to run them on try.bro.org (great web interface written by Justin, where you can include print statements like "print c$http; " in your scripts to check to see all the fields of http record, and then use them accordingly).
Thanks,
Fatema.