fix(telemetry): preserve built-in meter discovery

[yordis]

• Built-in database telemetry must remain discoverable when operators configure additional meter sources.
• Canonical instrumentation metadata prevents scope drift without changing emitted metrics.
• Instrumentation version metadata must remain self-contained across published layouts.

[cursor]

PR Summary

Low Risk
Observability registration and configuration only; emitted metric names and instrumentation logic are unchanged, with new unit tests covering meter list composition.

Overview
Built-in Core and Projections meters are always subscribed for OpenTelemetry/Prometheus, regardless of what operators put in metricsconfig.json Meters. The config list is now only for extra System.Diagnostics.Metrics sources; the sample config uses an empty array and the metrics docs describe the new behavior.

A new TelemetryMeterInstrumentation helper centralizes canonical meter names (EventStore.Core, EventStore.Projections.Core), GetNames (built-ins first, deduped, validated extras), and scope version from the assembly informational version. TelemetryMeterFactory, MetricsBootstrapper, and ProjectionsSubsystem use those constants instead of string literals; ClusterVNodeStartup calls GetNames(metricsConfiguration.Meters) when registering meters.

Unit tests cover GetNames ordering/deduping/validation and shared scope versioning.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: d1b1d870-38d3-4a3b-ad3d-fa1973b72370

📥 Commits

Reviewing files that changed from the base of the PR and between 198b648 and ce46a91.

📒 Files selected for processing (9)

• docs/diagnostics/metrics.md
• src/EventStore.ClusterNode/metricsconfig.json
• src/EventStore.Core.XUnit.Tests/OpenTelemetry/TelemetryMeterFactoryTests.cs
• src/EventStore.Core.XUnit.Tests/OpenTelemetry/TelemetryMeterInstrumentationTests.cs
• src/EventStore.Core/ClusterVNodeStartup.cs
• src/EventStore.Core/Diagnostics/TelemetryMeterFactory.cs
• src/EventStore.Core/Diagnostics/TelemetryMeterInstrumentation.cs
• src/EventStore.Core/MetricsBootstrapper.cs
• src/EventStore.Projections.Core/ProjectionsSubsystem.cs

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Walkthrough

Centralizes built-in telemetry meter names and instrumentation scope version handling, updates metrics registration to include built-in meters automatically, and adds tests for naming, version parsing, ordering, deduplication, and validation.

Changes

Telemetry instrumentation

Layer / File(s)	Summary
Instrumentation names and scope version src/EventStore.Core/Diagnostics/TelemetryMeterInstrumentation.cs, src/EventStore.Core/Diagnostics/TelemetryMeterFactory.cs, src/EventStore.Core/MetricsBootstrapper.cs, src/EventStore.Projections.Core/ProjectionsSubsystem.cs	Shared constants and scope version parsing replace hard-coded meter names and reflection-based version lookup.
Built-in meter registration src/EventStore.Core/ClusterVNodeStartup.cs, src/EventStore.ClusterNode/metricsconfig.json, docs/diagnostics/metrics.md	Metrics setup always registers Core and Projections meters while configuration supplies additional meter names.
Instrumentation behavior tests src/EventStore.Core.XUnit.Tests/OpenTelemetry/*	Tests cover names, version parsing, ordering, deduplication, and invalid inputs.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant metricsconfig.json
  participant ConfigureMetrics
  participant TelemetryMeterInstrumentation
  participant MeterProviderBuilder
  metricsconfig.json->>ConfigureMetrics: Meters array
  ConfigureMetrics->>TelemetryMeterInstrumentation: GetNames(additional meter names)
  TelemetryMeterInstrumentation-->>ConfigureMetrics: Built-in and additional names
  ConfigureMetrics->>MeterProviderBuilder: AddMeter(names)

Loading

Possibly related PRs

• TrogonStack/TrogonEventStore#451: Modifies the OpenTelemetry meter scope version and related tests.

Poem

A bunny found two meters bright,
Core and Projections, hopped in sight.
Extra names join the measured array,
Clean versions guide the way.
Tests keep every scope just right!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: preserving built-in meter discovery.
Description check	✅ Passed	The description matches the PR goals by describing built-in telemetry discovery, canonical metadata, and self-contained version metadata.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch yordis/fix-telemetry-instrumentation-contract

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 Biome (2.5.3)

src/EventStore.ClusterNode/metricsconfig.json

File contains syntax errors that prevent linting: Line 2: Expected a property but instead found '// must be 0, 1, 5, 10 or a multiple of 15'.; Line 3: End of file expected; Line 3: End of file expected; Line 3: End of file expected; Line 3: End of file expected; Line 7: End of file expected; Line 7: End of file expected; Line 7: End of file expected; Line 9: End of file expected; Line 11: End of file expected; Line 11: End of file expected; Line 11: End of file expected; Line 11: End of file expected; Line 13: End of file expected; Line 13: End of file expected; Line 13: End of file expected; Line 17: End of file expected; Line 19: End of file expected; Line 19: End of file expected; Line 19: End of file expected; Line 19: End of file expected; Line 21: End of file expected; Line 21: End of file expected; Line 21: End of file expected; Line 21: End of file expected; Line 23: End of file expected; Line 23: End of file expected; Line 23: End of file expected; Line 23: End of file expecte

... [truncated 1326 characters] ...

expected; Line 114: End of file expected; Line 116: End of file expected; Line 116: End of file expected; Line 119: Expected a property but instead found '// this is the most expensive metric, creating a histogram for each'.; Line 116: End of file expected; Line 119: End of file expected; Line 121: End of file expected; Line 121: End of file expected; Line 121: End of file expected; Line 122: End of file expected; Line 124: End of file expected; Line 124: End of file expected; Line 124: End of file expected; Line 150: End of file expected; Line 154: End of file expected; Line 154: End of file expected; Line 154: End of file expected; Line 203: End of file expected; Line 205: End of file expected; Line 205: End of file expected; Line 205: End of file expected; Line 279: End of file expected

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