Add support for OTEL_SDK_DISABLED environment variable

[hannahhaering]

Fixes #4155

Changes

• Implemented OTEL_SDK_DISABLED according to the OpenTelemetry specification
• Applied support across TracerProvider, MeterProvider, and LoggerProvider

Merge requirement checklist

• CONTRIBUTING 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)

[codecov]

Codecov Report

❌ Patch coverage is 94.11765% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.72%. Comparing base (0cd5701) to head (aa6027c).
⚠️ Report is 28 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...elemetry/Logs/Builder/LoggerProviderBuilderBase.cs	94.11%	1 Missing ⚠️
...emetry/Metrics/Builder/MeterProviderBuilderBase.cs	94.11%	1 Missing ⚠️
...lemetry/Trace/Builder/TracerProviderBuilderBase.cs	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6568      +/-   ##
==========================================
- Coverage   86.75%   86.72%   -0.04%     
==========================================
  Files         258      258              
  Lines       11910    11958      +48     
==========================================
+ Hits        10332    10370      +38     
- Misses       1578     1588      +10     

Flag	Coverage Δ
unittests-Project-Experimental	86.63% <94.11%> (+0.11%)	⬆️
unittests-Project-Stable	86.55% <94.11%> (-0.17%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...elemetry/Logs/Builder/LoggerProviderBuilderBase.cs	95.91% <94.11%> (-1.06%)	⬇️
...emetry/Metrics/Builder/MeterProviderBuilderBase.cs	96.15% <94.11%> (-1.07%)	⬇️
...lemetry/Trace/Builder/TracerProviderBuilderBase.cs	97.05% <94.11%> (-1.02%)	⬇️

... and 3 files with indirect coverage changes

[martincostello]

A better way to do this, IMHO, would be to:

1. Not set the value in the constructor
2. Let the test set the value it's interested in
3. Set it back to the original value when being disposed

You could use a similar pattern to this to implement it in a cross-cutting way, then the usage would be something like:

using (new EnvironmentVariableScope("OTEL_SDK_DISABLED", value))
{
    var builder = new LoggerProviderBuilderBase();

    using var provider = builder.Build();

    Assert.IsType(expected, provider);
}

[hannahhaering]

Thanks for the suggestion, I've done that.

Is there any way I can retry the workflow without a commit? Sometimes the build fails even though I have no errors (like right now).

[martincostello]

Not without write access to the repo, no.

[martincostello]

@CodeBlanch Would you mind taking a look at this please?

[CodeBlanch]

2 comments:

1. Would probably be good to add a log here. Don't want support tickets raised for missing telemetry when users have shot themselves in the foot 😄

2. This won't work for hosting scenarios. See line 80. This code is only invoked for manual/detached bootstrap. Something else will need to be done for hosting style. Ideally we would have a single solution for both but I haven't looked at where that might go.

[hannahhaering]

Thanks for the hint. Now it should work for both scenarios. Could you please check again?

[github-actions]

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[Copilot]

Pull Request Overview

This PR implements support for the OTEL_SDK_DISABLED environment variable according to the OpenTelemetry specification. When this environment variable is set to true, the SDK returns no-op provider implementations instead of functional ones, effectively disabling telemetry collection.

Key Changes:

• Added OTEL_SDK_DISABLED environment variable support across all three telemetry signals (tracing, metrics, logging)
• Introduced SdkConfigDefinitions class to centralize the environment variable name
• Created EnvironmentVariableScope test helper for managing environment variables in unit tests

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
SdkConfigDefinitions.cs	Defines the OTEL_SDK_DISABLED constant for centralized configuration
TracerProviderBuilderBase.cs	Checks OTEL_SDK_DISABLED and returns NoopTracerProvider when disabled
MeterProviderBuilderBase.cs	Checks OTEL_SDK_DISABLED and returns NoopMeterProvider when disabled
LoggerProviderBuilderBase.cs	Checks OTEL_SDK_DISABLED and returns NoopLoggerProvider when disabled
EnvironmentVariableScope.cs	Test utility class for temporarily setting environment variables
TracerProviderBuilderBaseTests.cs	Unit tests verifying SDK disable functionality for tracer provider
MeterProviderBuilderBaseTests.cs	Unit tests verifying SDK disable functionality for meter provider
LoggerProviderBuilderBaseTests.cs	Unit tests verifying SDK disable functionality for logger provider
CHANGELOG.md	Documents the new feature

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