From: Ivo van der Wijk <ivo@amaze.nl> Subject: Re: [Twisted-Python] Proposal: changes to reactor.clientTCP Date: Sun, 16 Jun 2002 01:06:51 +0200
On Sat, Jun 15, 2002 at 06:04:29PM +0200, Itamar Shtull-Trauring wrote:
Background: Ivo pointed out there's no way to differentiate between "no such hostname" and "connection refused". For that matter, connectionFailed has nothing to do with the protocol - why are we doing a callback on the protocol at all? It shouldn't be created if no connection was made.
Proposal: reactor.clientTCP accepts a protocol factory instead of a protocol, and only makes a protocol instance if connection was made. Additionally, it accepts an additional argument, failureCallback, which will get called with a status code (CONNECTION_REFUSED, NO_SUCH_HOSTNAME) or something when the connection fails. Protocol.connectionFailed goes bye-bye.
You know, I'm tempted to disagree with this because backwards-compatibility at this point is a really major argument to me at this point ... however, you guys make some really good arguments. It may even be possible, given this description, to make __init__, and not makeConnection, be the real "initializer" of a Protocol at this point. The inability to report these errors has also been an annoyance on the client-interface end of things for some time. There is an asymmetry between client and server-side connecting in IReactorTCP. In addition, Itamar's proposal would simultaneously eliminate the confusion currently surrounding Connectors, too; having a wrapper protocol *factory* would not pose the same efficiency concerns as a wrapper Protocol instance, since indirection would only happen when opening and closing the connection.
Comments?
Some people don't see a point in providing these errors, so I'll illustrate the issue with some more examples:
Also, being able to report these errors is important to judge at what level networking is misconfigured for the end-user, when they can't connect.
I agree with itamar that if these errors aren't handled in the protocol implementation, failure to connect shouldn't be there either.
After hearing this, so do I. Thank you for the bug report. -- | <`'> | Glyph Lefkowitz: Traveling Sorcerer | | < _/ > | Lead Developer, the Twisted project | | < ___/ > | http://www.twistedmatrix.com |