[pkg/translate/promremotewrite] downscale exponential histograms for prometheus

[krajorama]

Description:

Implement down-scaling of exponential histograms to Prometheus native histograms in Prometheus remote writer.
Configuration of down-scaling is TBD.

Link to tracking Issue:

Fixes: #17565

Testing:

Unit tests.

Documentation:

TBD

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: krajorama / name: George Krajcsovits (4ee29ff, bf70fc8, b8d41b6, 7f2d6ae, a7e0f92, 79b9a1a, c1e8359, f9475bc, e2a964f, af9e160, 8486261, 08f6cf4, d6499e6, 36ace23, b548ab7, 0b8f318, bafdf7b, a685502)
• ✅ login: kovrus / name: Ruslan Kovalov (af9e160)
• ✅ login: jpkrohling / name: Juraci Paixão Kröhling (413e3d0)
• ✅ login: Aneurysm9 / name: Anthony Mirabella (20fbc94)

[kovrus]

@krajorama please sing the CLA

[krajorama]

After some optimizations I got this benchmark compared to baseline:

goos: linux
goarch: amd64
pkg: github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheusremotewrite
cpu: AMD Ryzen 7 4700U with Radeon Graphics         
                            │ bench-orig.txt │           bench-new3.txt           │
                            │     sec/op     │   sec/op     vs base               │
ConvertBucketLayout/gap_0-8      17.30µ ± 1%   18.18µ ± 1%  +5.07% (p=0.000 n=10)
ConvertBucketLayout/gap_1-8      16.05µ ± 1%   16.91µ ± 1%  +5.34% (p=0.000 n=10)
ConvertBucketLayout/gap_2-8      15.61µ ± 1%   16.94µ ± 1%  +8.55% (p=0.000 n=10)
ConvertBucketLayout/gap_3-8      18.58µ ± 1%   19.47µ ± 1%  +4.76% (p=0.000 n=10)
geomean                          16.85µ        17.84µ       +5.92%

Looking at the profile, half the time is spent in reallocating the deltas and probably spans slices. That could be something to look at , although for small numbers it's probably fine.

[kovrus]

lgtm!

[jpkrohling]

I verified the tests, checking that the changes aren't breaking.

[jpkrohling]

CI is failing with an unrelated change, I'll rebase once the fix is merged.

[Aneurysm9]

Couple nits and a question. I'd approve but for the question about why apparently unrelated test changes seem to have been made.

[Dogacel]

Hoping this will resolve our issues with prometheus histograms 🙏 Putting the error we have seen here for visibility.

Exporting failed. The error is not retryable. Dropping data. {"kind": "exporter", "data_type": "metrics", "name": "prometheusremotewrite", "error": "Permanent error: cannot convert exponential to native histogram. Scale must be <= 8 and >= -4, was 20;