Consider a "dumb client" Single Page App where the domain logic resides on the server.
The UI events are delivered via Ajax, with the server responses flowing over SSE to update the UI.
The key question is thus latency and server load.
A simple experiment wires an Ajax call to the SSE event handler, where the call delivers a new data element over the SSE connection, forming an infinite loop.
That provides a simple measurement of the total request/response chain.
Both Play 2 and Jetty Continuations based implementations were tested, using Fedora Core 17, Google Chrome running on AMD Phenom II X6 1100T.
||CPU Load (%)
||JRE Load (%)
CPU Load is reported by top and JRE Load by JConsole.
Play uses Iteratees and NIO, which are both designed for concurrency rather than raw throughput.
A 10x difference is a surprising high cost to pay for the concurrency and expressiveness of the Play API.
The proposed user case would have less than a score of clients, which would be feasible even with a vanilla block Servlet implementation.