I have a load balanced service on AWS.
So the ELB evenly distributes the load across my servers.

Each server is running lighttpd that does logging and forwards the requests to my service (on the same machine).

I have written a new version of the service. It is installed and running on an EC2 machine test1 (basically a mirror of our current server but the new service running instead of the original) and I have done some preliminary tests that look good.

But what I would like to do is mirror a fraction of incoming traffic to the new version of the service so I can do some comparisons between an original version and the new version based on real traffic. Thus I was thinking I could modify one box behind the ELB to duplicate its traffic to the test1.

I was thinking I could modify the configuration of lighttpd so that each request is mirrored/duplicated. i.e. the original service keeps responding as before but a mirror request is sent to test1 but the reply is just dropped).

Unfortunately I have not been able to work this out.
Any ideas on how I could mirror the requests from one box to itself and test1.

Or any other ideas for testing.