HTTP 1.1, proxy servers, and failed connections

If a proxy server, when initiating a connection to the real server,
gets ECONNREFUSED, EHOSTDOWN, or EHOSTUNREACH, what error should
it return to the client? Some existing proxy servers return 500,
which seems to me particularly unhelpful, some return 503, which
to me doesn't seem equivalent. Is there a generally accepted
theory here? Is the HTTP 1.1 protocol deficient in this regard?
For implementing at-most-once semantics for requests, it would
be useful to know definitively (whenever possible) if the
server did not start working on the request. A 500 return doesn't
seem to provide any such guarantee, and it's not clear to me
if a 503 return does (the RFC says the client SHOULD handle 503
as it would 500, which might be taken to imply that there is no
guarantee). Can someone enlighten me? Thanks.

[Please reply to me directly, as I'm not on the alias.]

- Bob

Received on Friday, 10 May 2002 20:10:02 UTC