OTLP: Use optimized OTel metric translator, converting directly to Mimir format

[aknuds1]

What this PR does

Use optimized OTel metric translator in OTLP endpoint, converting directly to Mimir format.

The translation code is generated by downloading Go sources from mimir-prometheus, and transforming them to use Mimir protobuf types and enums via the gopatch tool. The generated files (_generated.go suffix) are checked into Git, and CI verifies that they are up to date with the mimir-prometheus version depended on.

The workflow should be that when we update the mimir-prometheus dependency, we should also execute make generate-otlp, to make sure we have the latest translation code. It's a minor hassle, but I think the performance gains are worth it.

TODO

• Modify CI check to generate code and check difference (suggested by @pracucci)
• Include gopatch in build image
• Put behind feature gate, to be on the safe side

Benchmark results

✗ benchstat main-otlphandler.txt direct-otlphandler.txt 
goos: linux
goarch: amd64
pkg: github.com/grafana/mimir/pkg/distributor
cpu: Intel(R) Xeon(R) Platinum 8358 CPU @ 2.60GHz
                        │ main-otlphandler.txt │      direct-otlphandler.txt       │
                        │        sec/op        │   sec/op     vs base              │
OTLPHandler/protobuf-32            415.2µ ± 1%   391.5µ ± 0%  -5.71% (p=0.002 n=6)
OTLPHandler/JSON-32                606.9µ ± 1%   583.4µ ± 1%  -3.88% (p=0.002 n=6)
geomean                            502.0µ        477.9µ       -4.80%

                        │ main-otlphandler.txt │       direct-otlphandler.txt        │
                        │         B/op         │     B/op      vs base               │
OTLPHandler/protobuf-32           391.0Ki ± 0%   272.8Ki ± 0%  -30.24% (p=0.002 n=6)
OTLPHandler/JSON-32               473.1Ki ± 0%   354.8Ki ± 0%  -25.00% (p=0.002 n=6)
geomean                           430.1Ki        311.1Ki       -27.67%

                        │ main-otlphandler.txt │      direct-otlphandler.txt       │
                        │      allocs/op       │  allocs/op   vs base              │
OTLPHandler/protobuf-32            5.129k ± 0%   5.122k ± 0%  -0.14% (p=0.002 n=6)
OTLPHandler/JSON-32                8.162k ± 0%   8.155k ± 0%  -0.09% (p=0.002 n=6)
geomean                            6.470k        6.463k       -0.11%

Which issue(s) this PR fixes or relates to

Checklist

• Tests updated.
• Documentation added.
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
• about-versioning.md updated with experimental features.

[github-actions]

Building new version of mimir-build-image. After image is built and pushed to Docker Hub, a new commit will automatically be added to this PR with new image version grafana/mimir-build-image:pr7957-d7652788a7. This can take up to 1 hour.

[github-actions]

Not building new version of mimir-build-image. This PR modifies mimir-build-image/Dockerfile, but the image grafana/mimir-build-image:pr7957-d7652788a7 already exists.

[github-actions]

Not building new version of mimir-build-image. This PR modifies mimir-build-image/Dockerfile, but the image grafana/mimir-build-image:pr7957-d7652788a7 already exists.

[aknuds1]

@pstibrany do you think there's any need to test this in a dev cell first, or should we be good to go (as it's just a transformation from Prom sources)?

[pstibrany]

Thank you Arve, nice work!

[pstibrany]

@pstibrany do you think there's any need to test this in a dev cell first, or should we be good to go (as it's just a transformation from Prom sources)?

As per Slack discussion, we may want to have a temporary feature flag to enable new, or use old translation code, in case we find a problem with the new code. After we successfully roll this out to our prod, we can remove the flag and old code.

[github-actions]

Not building new version of mimir-build-image. This PR modifies mimir-build-image/Dockerfile, but the image grafana/mimir-build-image:pr7957-d7652788a7 already exists.

[github-actions]

Not building new version of mimir-build-image. This PR modifies mimir-build-image/Dockerfile, but the image grafana/mimir-build-image:pr7957-d7652788a7 already exists.

[github-actions]

Not building new version of mimir-build-image. This PR modifies mimir-build-image/Dockerfile, but the image grafana/mimir-build-image:pr7957-d7652788a7 already exists.

[aknuds1]

As per Slack discussion, we may want to have a temporary feature flag to enable new, or use old translation code, in case we find a problem with the new code. After we successfully roll this out to our prod, we can remove the flag and old code.

@pstibrany flag added w/ true for default (is false preferable?), PTAL.

[pstibrany]

Thank you.