by peter@scraperwiki.com:

This is a follow-up to
https://groups.google.com/d/topic/golang-dev/-pPRjs46QIk/discussion.

With the following code:

http://play.golang.org/p/Qrqg2XmuRz

Consider a long running http handler (L19) which hypothetically uses (e.g, CPU)
resources until the connection is closed. The handler is aware of connection closure
through: w.(http.CloseNotifier).CloseNotify().

If we proxy to that handler via a http.ReverseProxy, closes don't make it to the target
server (and it keeps consuming resources indefinitely).

One can see the correct behaviour when querying the original internal handler directly
and if line 72 (useExternal=true) is uncommented, the demo deadlocks.

The deadlock is because the internal server is waiting forever, since it never received
a close notification.

One can observe the same behaviour with the same demo application by using cURL from the
console and aborting cURL. If aborting against the internal server, then "[server]
Close Notified!" is seen. If aborting against the external, it is never seen.