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On 08/28/2015 09:34 AM, Valeriy Ponomaryov wrote:
> Dmitriy,
>
> New tests, that cover new functionality already know which API version
> they require. So, even in testing, it is not needed. All other existing
> tests do not require API update.

Yeah, but you can't be sure that your change does not break the world, 
until you merge it and start updating tests. Probably it's not that 
important for projects who have their integration tests in-tree though..

>
> So, I raise hand for restricting "latest".
>
> On Fri, Aug 28, 2015 at 10:20 AM, Dmitry Tantsur <dtantsur at redhat.com
> <mailto:dtantsur at redhat.com>> wrote:
>
>     On 08/27/2015 09:38 PM, Ben Swartzlander wrote:
>
>         Manila recently implemented microversions, copying the
>         implementation
>         from Nova. I really like the feature! However I noticed that
>         it's legal
>         for clients to transmit "latest" instead of a real version number.
>
>         THIS IS A TERRIBLE IDEA!
>
>         I recommend removing support for "latest" and forcing clients to
>         request
>         a specific version (or accept the default).
>
>
>     I think "latest" is needed for integration testing. Otherwise you
>     have to update your tests each time new version is introduced.
>
>
>
>         Allowing clients to request the "latest" microversion guarantees
>         undefined (and likely broken) behavior* in every situation where a
>         client talks to a server that is newer than it.
>
>         Every client can only understand past and present API
>         implementation,
>         not future implementations. Transmitting "latest" implies an
>         assumption
>         that the future is not so different from the present. This
>         assumption
>         about future behavior is precisely what we don't want clients to
>         make,
>         because it prevents forward progress. One of the main reasons
>         microversions is a valuable feature is because it allows forward
>         progress by letting us make major changes without breaking old
>         clients.
>
>         If clients are allowed to assume that nothing will change too
>         much in
>         the future (which is what asking for "latest" implies) then the
>         server
>         will be right back in the situation it was trying to get out of
>         -- it
>         can never change any API in a way that might break old clients.
>
>         I can think of no situation where transmitting "latest" is
>         better than
>         transmitting the highest version that existed at the time the
>         client was
>         written.
>
>         -Ben Swartzlander
>
>         * Undefined/broken behavior unless the server restricts itself
>         to never
>         making any backward-compatiblity-breaking change of any kind.
>
>
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>
> --
> Kind Regards
> Valeriy Ponomaryov
> www.mirantis.com <http://www.mirantis.com>
> vponomaryov at mirantis.com <mailto:vponomaryov at mirantis.com>
>
>
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