Fix compiled logproto protobuf

[pracucci]

What this PR does / why we need it:

The PR #1133 has upgraded golangci-lint and thus the loki-build-image has been rebuilded and a new version published (0.7.3).

The rebuild of the image has installed the latest versions of the deps specified in the loki-build-image/Dockerfile, including protoc-gen-gogoslick which I think is the cause of a change to pkg/logproto/logproto.pb.go.

We didn't notice it, because in the Makefile the %.pb.go target is not a phony one, so the logproto.proto is recompiled only once its timestamp change. However, it should be recompiled also whenever the tooling change and it may be quite difficult to remember it, so I'm proposing to enforce it when running make check-generated-files.

Unfortunately, the only idea I've got to enforce protoc whenever we run make check-generated-files is a bit hacky. I'm open to better ideas.

Special notes for your reviewer:

• I started investigating it when I've seen that the build https://cloud.drone.io/grafana/loki/815 failed, but a restart https://cloud.drone.io/grafana/loki/816 succeeded and wanted to find the root of the flaky build

Checklist

• Documentation added
• Tests updated

[joe-elliott]

I like the idea of always force checking on protos generation and I'm not good enough with Makefiles to suggest anything better. Generally, I like this change.

I am, however, concerned about changing logproto.pb.go this close to releasing 0.4.0. Should we pin the tooling in the Dockerfile instead and merge the updated logproto.pb.go after cutting 0.4.0?

[pracucci]

Should we pin the tooling in the Dockerfile instead [...]?

@joe-elliott You mean pin the version of the following packages in loki-build-image/Dockerfile, release a new version of loki-build-image, upgrade to the new image and revert the changes to logproto.pb.go?

• github.com/golang/protobuf/protoc-gen-go
• github.com/gogo/protobuf/protoc-gen-gogoslick
• github.com/gogo/protobuf/gogoproto

[joe-elliott]

Yes, that feels safer to me, or just merge this change after 0.4.0 is cut?

@slim-bean Thoughts either way?

Recent changes to the build image have caused inconsistency in our build pipeline outlined by marco above.

Options are:

• merge his fix now which includes changes to logproto.pb.go due to a version change in protobuf tooling
• pin the protobuf tooling for now to make CI more consistent and keep logproto.pb.go unchanged
• wait til after 0.4.0 and merge, but CI might be a bit flaky until then.

[slim-bean]

I like the idea of pinning the versions of golang and gogo protobuf and making a new build image 👍

[pracucci]

@joe-elliott @slim-bean May you check the changes, please? I've already advanced the loki-build-image version even if has not been published yet (I've tested it locally). If we're good with it, is there any automation to build and publish loki-build-image:0.7.4? (I've seen make loki-build-image tags it with the current branch name).

[slim-bean]

LGTM, one question/thought if we should also pin the yacc version

[pracucci]

@slim-bean I've pushed the loki-build-image:0.7.4 and added a Makefile target to do it. The CI build passes. If you don't see any issue, should be ready to merge.