[ovs-dev] [PATCH ovn v4] Document process for compatibility between OVS and OVN.

[Mark Michelson]

On 10/16/19 4:36 PM, Han Zhou wrote:
> 
> 
> On Tue, Oct 8, 2019 at 2:12 PM Mark Michelson <mmichels at redhat.com 
> <mailto:mmichels at redhat.com>> wrote:
>  > +
>  > +Developers who are making changes to both OVS and OVN at the same 
> time *must*
>  > +contribute the OVS change first and ensure it is merged upstream before
>  > +submitting the OVN change. This way, OVN should never be in a state 
> where it
>  > +will not compile.
>  > +
> 
> Hi Mark, I have a question here after reading your patch for release 
> documentation. If OVN is released more frequently than OVS, then there 
> is a chance that even developers make sure the related OVS change is 
> merged before OVN change, the next OVN release still can't compile with 
> the latest released OVS. It would only compile with the OVS master which 
> is not released yet. Is this a problem?

Hi Han, We talked about this some during the OVN IRC meeting today, but 
I figure it's good to have the result of that documented here.

The risks here are the following:
1) There may be a bug in OVS at the time that OVN is released.
2) Compiling against an arbitrary commit of OVS may make it difficult to 
reproduce/debug builds of OVN.
3) When distributing tarballs, people may be tempted to deploy the 
arbitrary OVS commit that OVN was compiled against rather than a 
supported released version.

I'm going to downplay (1) somewhat. When it comes to compilation, the 
relevant bugs in OVS are limited to the library functions that OVS 
exports. The most common types of bugs in these functions would be 
discovered during OVN testing. And when it comes to the more insidious 
bugs (memory leaks, off-by-one errors, etc.), those aren't necessarily 
going to be any less likely to be fixed in a release vs. a non-release 
commit of OVS.

Regarding (2), Justin suggested noting the OVS git commit necessary for 
building OVN. That way, we have an audit trail of what OVS commit was 
used for building any particular release of OVN.

And I'm not sure about what to do about (3).

> 
> Thanks,
> Han