Re: [hybi] Versioning is a anti-pattern

[Willy Tarreau <[e-mail]>]

On Mon, Sep 06, 2010 at 02:41:26PM +0900, "Martin J. Dürst" wrote:
> Hello Adam,
> 
> On 2010/09/04 11:06, Adam Barth wrote:
> >On Thu, Sep 2, 2010 at 11:25 AM, Daniel Stenberg<[e-mail]>  wrote:
> >>On Wed, 1 Sep 2010, Adam Barth wrote:
> >>>Please don't add versioning to the protocol.  Versioning is a 
> >>>anti-pattern
> >>>for the web.
> >>
> >>We've seen this mentioned before on this list but without a lot of
> >>clarifications and I'm curious:
> >>
> >>What are the other transfer protocols for which versioning have failed so
> >>significantly that versioning in protocols can be called an anti-pattern?
> >
> >Versioning has been a big pain point for TLS.  Here's a presentation
> >that outlines some recent implementation experience:
> >
> >http://www.ietf.org/proceedings/65/slides/tls-6.pdf
> >
> >I encourage you to read through the presentation (it's pretty short).
> 
> This is indeed discouraging. TLS server side implementers seem to be 
> rather challenged. For a security-related protocol, that's rather bad 
> indeed. I very much hope WS implementers can do a better job.

This presentation exactly outlines what is wrong when versions are used :
to make it mandatory to support a certain feature set without full
upgradability from the previous protocol. Early adopters do not completely
implement the spec and cause the trouble. In my opinion, a version should
be used *in conjunction* with a negociation, in order to announce :
  - a behaviour on the wire (could have been useful for WS with the new
    framing)
  - the highest, fully supported standard set of feature, in order not
    to have to announce them all.

There should be no problem always announcing v1.0 with a set of 20
extensions or announcing v1.1 with a set of 2 extensions. And in turn,
the spec should not make complex extensions mandatory, or it risks
having some users not support them once a protocol upgrade requires a
version bump.

Willy