Basically, under what circumstances should Callback vs Polling be use when implementing asynchronous web services? What are the pros and cons of each?...are there any guidelines or metrics out there?
-Callback being the mechanism where the client provides a callback handler to process the response when eventually acquired.
-Polling being the mechanism where the client after submitting a requests gets a response object that is polled by the client to determine if the server has finish executing its workload and its ready to return.
Point of interest are:
-reponse time on the client side
-server load
-network impact
-performance of multiple callback calls vs multiple polling calls, client and server side