[Exporter.OTLP] Optimize GetHeaders by Spans

[nimanikoo]

Title: Optimize header parsing in GetHeaders method by replacing Split with Span to enhance performance and reduce allocations. OtlpExporterOptionsExtensions.cs

Design discussion issue: 6180
#6180

Changes

Refactored the GetHeaders method to utilize Span<T> for parsing header strings, aiming to improve performance by minimizing memory allocations. This change is inspired by techniques discussed in the following articles:

• [Optimising .NET Code: Avoiding Allocations Using Span](https://endjin.com/blog/2023/09/optimising-dotnet-code-4-avoiding-allocations-using-span-t)
• [Improving C# Performance with Span](https://www.jitbit.com/alexblog/309-improving-c-performance-with-spant/)

By implementing these optimizations, I hope to contribute to the project's performance enhancements and am eager to assist further in its development.

Merge requirement checklist

• [CONTRIBUTING](https://github.com/open-telemetry/opentelemetry-dotnet/blob/main/CONTRIBUTING.md) guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: nimanikoo / name: nima nikoonazar (511c8cb, d73cc15, cda3c88, bb61cd6, 65e0744, e490141)
• ✅ login: Kielek / name: Piotr Kiełkowicz (3820974, 094907a, 496228b)

[rajkumar-rangaraj]

@nimanikoo Could you please add a benchmark to measure performance improvement?

[nimanikoo]

@rajkumar-rangaraj

Sure! I’ll add a benchmark to measure the performance improvement.

I’ll use BenchmarkDotNet to compare the old and new implementations of GetHeaders. The benchmark will measure execution time and memory allocations to demonstrate the benefits of using Span.

I’ll update the PR soon with the benchmark results. Thanks for the suggestion!

[nimanikoo]

@rajkumar-rangaraj I benchmarked two implementations of the GetHeaders method—GetHeadersOld and GetHeadersNew—to evaluate the impact of code optimization.

System Specifications:

• Operating System: Linux Mint 21.3
• Processor: Intel Core i5-10300H CPU 2.50GHz
• .NET SDK: 8.0.112
• Kernel: 5.15.0-127-generic

Benchmark Results:

Method	Mean	Error	StdDev	Ratio
GetHeadersOld	353.7 ns	1.69 ns	1.41 ns	1.00
GetHeadersNew	226.5 ns	0.32 ns	0.30 ns	0.64

These results indicate that GetHeadersNew performs 36% faster than GetHeadersOld. This improvement is likely due to optimizations such as utilizing Span<T> for more efficient memory handling.

[nimanikoo]

I modified only GetHeaders method, making changes inside the method without altering its input parameters or return result. However, I'm unable to identify the issue causing the tests and build to fail. Could you please help me in resolving this?

@rajkumar-rangaraj

[rajkumar-rangaraj]

I modified only GetHeaders method, making changes inside the method without altering its input parameters or return result. However, I'm unable to identify the issue causing the tests and build to fail. Could you please help me in resolving this?

@rajkumar-rangaraj

In your local development environment, performing a release build should reveal these errors. Here are the errors from CI:

Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(52,1): error SA1137: Elements should have the same indentation (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1137.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=net462]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(96,1): error SA1507: Code should not contain multiple blank lines in a row (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1507.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=net8.0]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(96,1): error SA1507: Code should not contain multiple blank lines in a row (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1507.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=net462]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(52,1): error SA1137: Elements should have the same indentation (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1137.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=net8.0]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(52,1): error SA1137: Elements should have the same indentation (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1137.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=net9.0]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(96,1): error SA1507: Code should not contain multiple blank lines in a row (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1507.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=net9.0]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(52,1): error SA1137: Elements should have the same indentation (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1137.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=netstandard2.0]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(96,1): error SA1507: Code should not contain multiple blank lines in a row (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1507.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=netstandard2.0]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(52,1): error SA1137: Elements should have the same indentation (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1137.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=netstandard2.1]
Error: D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OtlpExporterOptionsExtensions.cs(96,1): error SA1507: Code should not contain multiple blank lines in a row (https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1507.md) [D:\a\opentelemetry-dotnet\opentelemetry-dotnet\src\OpenTelemetry.Exporter.OpenTelemetryProtocol\OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj::TargetFramework=netstandard2.1]

[nimanikoo]

Ah, I figured out what the problem was.
Thank you, I'll fix it.
I thought there was a critical problem that would interfere with the project.

[nimanikoo]

I've tried to fix all the indentation issues mentioned by the code analyzer. Is there anything else I should fix?
Thank you for your help and the time you’re putting into this.
@rajkumar-rangaraj

[Kielek]

LGTM with minor improvement and one direct build fix.

[xiang17]

Suggested change

	headersSpan = [];
	headersSpan = ReadOnlySpan<char>.Empty;

[Kielek]

Why? The [] is the recommended way by the analyzers. IDE0300/IDE0301 as I remember?

[xiang17]

The benchmarks results look good. However, it doesn't have any memory related stats. Can you run with the -m option to enables MemoryDiagnoser and prints memory statistics.

[xiang17]

How much code coverage do the existing unit test cases have for this method? Since the sole purpose of this PR is to update the parse logic, it might be good to add more test cases.

Can you also include the benchmark code in the PR description or somewhere in the comment? No need to include it in the code change.

[nimanikoo]

Based on the references used by this method, I’ve run benchmarks in two different scenarios with the same conditions and system as mentioned in the previous comments, and this is the result. Do you think any further changes are needed or is there anything else I should do?
@xiang17
#2 OtlpHttpExporterBenchmarks

old code

new code