We're developing an new server to replace an old one, and want to put the side by side for before & after tests - so that we can compare the end result and find the discrepancies.
The input to both services (old and new) is HTTP requests (mostly if not all GET, but possibly also POST), we need to have traffic coming to the old server duplicated and sent also to the new server (not instead). of course we will need to do some slight rewriting on the Hostname and port in the request to avoid an endless loop.
Old server is running on Apache (PHP), new one is Jetty (Java, Dropwizard)
There must be a way to do this, I just can't find the keywords for the Google search I guess...