Hi BenchmarkDotNet team,

I'd like to propose and contribute a new OpenMetrics exporter to BenchmarkDotNet. This would allow users to generate performance benchmark output in the OpenMetrics format, which is compatible with GitLab's built-in Metrics Reports feature.

Motivation

GitLab supports ingesting metrics in the OpenMetrics format via a metrics.txt artifact. This opens the door for integrating performance benchmarks directly into CI pipelines, making performance regressions first-class citizens of the CI/CD process. BenchmarkDotNet already supports various exporters (CSV, Markdown, HTML, etc.), but not yet OpenMetrics.

Adding an OpenMetricsExporter would allow:

• Comparing benchmark results between commits/MRs in GitLab pipelines
• Alerting on performance regressions directly from the GitLab UI
• Seamless integration with DevOps workflows that rely on GitLab CI

Proposed Scope

• A new OpenMetricsExporter implementation
• Support for writing metrics.txt files in the OpenMetrics format
• Mapping relevant benchmark measurements (e.g., mean, error, stdev, ops/sec) to OpenMetrics-compatible metric types (e.g., gauge)
• Optional: labels for benchmark class/method/config to support filtering and grouping

Example output (simplified)

# TYPE benchmark_duration_seconds gauge
benchmark_duration_seconds{benchmark="MyBenchmark.MethodA",job="Default"} 0.000123

# TYPE benchmark_ops_per_second gauge
benchmark_ops_per_second{benchmark="MyBenchmark.MethodA",job="Default"} 8120.0

Benefits

• Enables performance regression detection as part of the CI process
• Aligns with modern DevOps practices
• Bridges BenchmarkDotNet with GitLab-native tooling

I'm happy to contribute the implementation and open a PR if the maintainers agree with the direction.

Thanks for your amazing work on this project!