[Geneva] Optimize metrics exporter serializer

[pentp]

Higher-level changes include serializing resource level tags only once for OtlpProtobufMetricExporter.
Most of the changes are just low-level optimizations for efficient buffer access, single-pass string encoding, etc.

BenchmarkDotNet v0.14.0, Windows 10 (10.0.19045.5247/22H2/2022Update)
Intel Core i7-7700K CPU 4.20GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical cores
.NET SDK 9.0.200-preview.0.24575.35
  [Host]     : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2
  DefaultJob : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2

BASELINE	Mean	Error	StdDev	Allocated
SerializeCounterMetricItemWith3Dimensions	162.62 ns	1.355 ns	1.267 ns	-
SerializeCounterMetricItemWith4Dimensions	179.49 ns	1.450 ns	1.356 ns	-
ExportCounterMetricItemWith3Dimensions	181.36 ns	1.158 ns	1.083 ns	-
ExportCounterMetricItemWith4Dimensions	199.94 ns	0.673 ns	0.597 ns	-
SerializeHistogramMetricItemWith3Dimensions	275.98 ns	2.971 ns	2.634 ns	-
SerializeHistogramMetricItemWith4Dimensions	296.83 ns	3.165 ns	2.961 ns	-
ExportHistogramMetricItemWith3Dimensions	299.81 ns	2.303 ns	1.798 ns	-
ExportHistogramMetricItemWith4Dimensions	334.96 ns	6.634 ns	6.813 ns	-
SerializeCounterMetricItemWith3Dimensions_Otlp	375.91 ns	2.072 ns	1.730 ns	48 B
SerializeCounterMetricItemWith4Dimensions_Otlp	433.05 ns	2.902 ns	2.715 ns	48 B
ExportCounterMetricItemWith3Dimensions_Otlp	378.03 ns	2.738 ns	2.427 ns	48 B
ExportCounterMetricItemWith4Dimensions_Otlp	436.66 ns	2.883 ns	2.697 ns	48 B
SerializeHistogramMetricItemWith3Dimensions_Otlp	468.75 ns	2.976 ns	2.784 ns	48 B
SerializeHistogramMetricItemWith4Dimensions_Otlp	519.62 ns	3.066 ns	2.560 ns	48 B
ExportHistogramMetricItemWith3Dimensions_Otlp	470.72 ns	4.137 ns	3.668 ns	48 B
ExportHistogramMetricItemWith4Dimensions_Otlp	531.59 ns	3.729 ns	3.305 ns	48 B

PR	Mean	Error	StdDev	Allocated
SerializeCounterMetricItemWith3Dimensions	134.24 ns	0.803 ns	0.671 ns	-
SerializeCounterMetricItemWith4Dimensions	152.22 ns	0.909 ns	0.850 ns	-
ExportCounterMetricItemWith3Dimensions	131.44 ns	1.095 ns	0.971 ns	-
ExportCounterMetricItemWith4Dimensions	147.23 ns	1.459 ns	1.365 ns	-
SerializeHistogramMetricItemWith3Dimensions	191.51 ns	1.098 ns	0.973 ns	-
SerializeHistogramMetricItemWith4Dimensions	211.51 ns	1.603 ns	1.421 ns	-
ExportHistogramMetricItemWith3Dimensions	190.01 ns	1.047 ns	0.928 ns	-
ExportHistogramMetricItemWith4Dimensions	204.39 ns	1.226 ns	1.147 ns	-
SerializeCounterMetricItemWith3Dimensions_Otlp	145.69 ns	1.172 ns	1.096 ns	-
SerializeCounterMetricItemWith4Dimensions_Otlp	161.80 ns	1.177 ns	1.101 ns	-
ExportCounterMetricItemWith3Dimensions_Otlp	146.14 ns	0.812 ns	0.678 ns	-
ExportCounterMetricItemWith4Dimensions_Otlp	191.51 ns	0.835 ns	0.697 ns	-
SerializeHistogramMetricItemWith3Dimensions_Otlp	188.66 ns	1.410 ns	1.319 ns	-
SerializeHistogramMetricItemWith4Dimensions_Otlp	204.14 ns	0.871 ns	0.727 ns	-
ExportHistogramMetricItemWith3Dimensions_Otlp	185.20 ns	0.781 ns	0.692 ns	-
ExportHistogramMetricItemWith4Dimensions_Otlp	208.30 ns	1.162 ns	1.030 ns	-

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[pentp]

Should I update the changelog also or what else is missing from the PR?

[Kielek]

@TimothyMothra, @xiang17, FYI

[rajkumar-rangaraj]

Should I update the changelog also or what else is missing from the PR?

I will review the PR in couple of days.

[rajkumar-rangaraj]

There is a test failure, could you please check?

[rajkumar-rangaraj]

Wondering why this check had been removed here if (data != null && data.Length != 0)

[rajkumar-rangaraj]

@pentp First of all, thank you for your hard work on this PR! I really appreciate the effort you’ve put into improving the Geneva Exporter. I can see this PR is bringing meaningful improvements.

However, this PR contains a mix of unrelated changes, which makes it quite complex to review in a single pass. To facilitate an easier and more effective review, I’d recommend breaking it into multiple PRs.

I have reviewed the following files, which contain miscellaneous improvements that can remain in one PR:

src/OpenTelemetry.Exporter.Geneva/Metrics/GenevaMetricExporter.cs
src/OpenTelemetry.Exporter.Geneva/Metrics/OtlpProtobuf/FieldNumberConstants.cs
src/OpenTelemetry.Exporter.Geneva/Metrics/OtlpProtobuf/TimestampHelpers.cs
src/OpenTelemetry.Exporter.Geneva/Metrics/Transport/MetricWindowsEventTracingDataTransport.cs

For better maintainability and clarity, I suggest moving the TlvMetricExporter and OtlpProtobuf changes into separate PRs. This will make it easier to review, test, and merge.

Thanks again for your contribution! Looking forward to the updated PRs.