I get "Failed to load resource: the server responded with a status of 502 (Proxy Error)" on the browser when I do not do any activity on qlik document for 15 mins. On investigating the logs I see "Session expired after idle time" in the session log everytime I see 502 in browser. What parameters in QMC do I need to tune. I checked all possible ones. And there is no pattern in frequency of time outs.
Those are standard values, allowing any user to do nothing for at most 30 minutes before the session will be terminated.
IMHO a proxy serves to cache content from the actual web site when you repeatedly request the same pages. Why are you using a proxy to visit the QLikView AccessPoint? I'm not a proxy specialist, but the QlikView AccessPoint should be configured as transparent in your proxy server (meaning that the proxy won't cache anything) or your proxy settings shouldn't be used when visiting the AP.
Are you using IE? Then open Internet options->Connections->LAN settings (or something similar)->Proxyserver->Advanced and add your AP server to the exception list.. Or ask your sysadmin to create an exception for you.
It doesn't matter how you access your QlikView documents, it's the QVS service that manages Qlikview documents, and the session timeout settings are QVS properties anyway.
Chrome uses the same system settings for accessing web sites through a proxy as IE does. In Chrome, select Menu->Settings->Show Advanced Settings->Network->Change proxy settings to add the Qlikview site you are referencing in your iframe to your proxy exceptions list (meaning that you do NOT want to use your proxy to access this qlikview site)