Re: [BuildStream] BuildGrid and BuildStream 1.4 and API concerns

[Jürg Billeter <j bitron ch>]

Hi Tristan,

On Mon, 2018-11-26 at 18:01 +0900, Tristan Van Berkom via BuildStream-list wrote:
> My question to the developers involved in BuildGrid is:
>
>   What is the status of API stability of BuildGrid regarding the
>   protocols and any parts which BuildStream will directly be
>   interfacing with ?
>
>   Are there any chances that changes in BuildGrid due to it's being
>   under development, could break BuildStream users ? I.e. can BuildGrid
>   be safely upgraded without breaking BuildStream and without requiring
>   lock-step upgrades of both BuildStream and BuildGrid ?
>
> I think the answers for this are already "BuildGrid's BuildStream
> facing APIs are already stable, since they are a standard grpc protocol
> that is not allowed to break it's API at all" and "No, upgrades to a
> deployed BuildGrid cannot break interfacing BuildStream clients".

While I believe this to be correct for the basic API, there is no
standardization yet for the platform attributes for the execution
environment. This is also currently not implemented on either side. In
BuildStream this is considered a blocker for 1.4, see #775 and !969.
For BuildGrid see #104.

While this is not ideal, I expect it to be reasonable for BuildGrid to
support the platform attributes BuildStream 1.4 will use for the
foreseeable future, even if the eventual upstream standard may differ
in some details. I.e., BuildGrid should be able to easily support both,
in case they will not match.

Assuming the standardization happens between BuildStream 1.4 and 1.6,
BuildStream 1.6 may no longer work with older BuildGrid, which I think
is acceptable as BuildGrid hasn't had a stable release yet. If
BuildGrid's first stable release happens before the standardization, it
should still be straight forward to backport the standardized values.

Jürg