[BuildStream] BuildGrid and BuildStream 1.4 and API concerns

[Tristan Van Berkom <tristan vanberkom codethink co uk>]

Hi all,

BuildStream 1.4 will be coming out with support for remote execution,
which in a way means optional dependency on BuildGrid.

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".

But please think about this.

If the APIs are not stable yet, I would propose that we consider a
bundled distribution of a version of BuildGrid that is known to work
with BuildStream 1.4, to be distributed *with* BuildStream 1.4, only as
a temporary measure until we can be sure that we don't break users in
the meantime.

Cheers,
    -Tristan