Add a timestamp to web2.server.Request for performance tracking

[Cyrus Daboo]

It is useful to record in an access log the total time taken to process a request. I propose adding an attribute to the init method of Request that records the time when the request object is created. That timestamp can then be used later during the processing of the request to determine elapsed time or to print the total request time in an access log when the request is complete. This will also aid with tracking down performance issues by making it easy to log elapsed time during different portions of request processing.

Proposed patches attached. One adds the timestamp to the Request object, the other modifies the access log output to include the total request elapsed time in milliseconds.

[exarkun]

There should be test coverage for this functionality. Preferably the clock used (time.time) should be parameterized so that the tests are deterministic. It might also be useful if either wallclock time or CPU time could be logged (or both), but that's more a new feature request than criticism of this patch.

I'm not sure about this, but I think the current log format is based some standard (de facto or otherwise). Does the addition of a new field break this?

[thijs]

web2's gone.