[OpenTelemetry] Handle duplicate sampler attributes by xiang17 · Pull Request #7558 · open-telemetry/opentelemetry-dotnet

xiang17 · 2026-07-28T22:46:19Z

Fixes Azure/azure-sdk-for-net#58948
Design discussion issue #

Changes

Replaced ActivityTagsCollection.Add with indexer assignment when applying sampler attributes during Activity creation.

This prevents Activity creation from throwing when multiple matching TracerProvider instances return an attribute with the same key. The behavior now matches the existing legacy Activity path, which applies sampler attributes using Activity.SetTag replacement semantics.

When multiple samplers return different values for the same key, the value from the last invoked listener is retained.

Added a regression test with two providers that return the same attribute key.

Motivation

OpenTelemetry supports multiple TracerProvider instances, and .NET ActivitySource invokes every matching ActivityListener while creating one Activity. These listeners contribute to the Activity's shared sampling-tag collection.

Previously, the second provider failed while adding a duplicate key:

System.InvalidOperationException: The collection already contains item with same key 'duplicate-sampler-attribute'

This exception prevents Activity creation and, in ASP.NET Core TestHost, may present as a request timeout.

Validation

Before the fix, the new regression test failed in TracerProviderSdk.ComputeActivitySamplingResult.

After the fix:

TracerProviderSdkDuplicateSamplerAttributesUseLastValue passed.
Full TracerProviderSdkTests class passed: 67 tests.
Production source formatting verification passed.

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)~~

opentelemetry-pr-dashboard · 2026-07-28T22:47:23Z

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Merged · refreshed 2026-07-29 06:33 UTC

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codecov · 2026-07-28T23:05:18Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.39%. Comparing base (9440662) to head (f081445).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7558      +/-   ##
==========================================
- Coverage   90.43%   90.39%   -0.04%     
==========================================
  Files         290      290              
  Lines       15989    15989              
==========================================
- Hits        14459    14453       -6     
- Misses       1530     1536       +6

Flag	Coverage Δ
unittests-Project-Experimental	`90.35% <100.00%> (-0.17%)`	⬇️
unittests-Project-Stable	`90.43% <100.00%> (-0.02%)`	⬇️

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

Files with missing lines	Coverage Δ
src/OpenTelemetry/Trace/TracerProviderSdk.cs	`98.72% <100.00%> (ø)`

... and 3 files with indirect coverage changes

cijothomas

LGTM.

….0 (#1316) Updated [OpenTelemetry.Exporter.OpenTelemetryProtocol](https://github.com/open-telemetry/opentelemetry-dotnet) from 1.17.0 to 1.18.0. <details> <summary>Release notes</summary> _Sourced from [OpenTelemetry.Exporter.OpenTelemetryProtocol's releases](https://github.com/open-telemetry/opentelemetry-dotnet/releases)._ ## 1.18.0 For highlights and announcements pertaining to this release see: [Release Notes > 1.18.0](https://github.com/open-telemetry/opentelemetry-dotnet/blob/main/RELEASENOTES.md#1180). The following changes are from the previous release [1.17.0](https://github.com/open-telemetry/opentelemetry-dotnet/releases/tag/core-1.17.0). * NuGet: [OpenTelemetry v1.18.0](https://www.nuget.org/packages/OpenTelemetry/1.18.0) * Fixed self-diagnostics log lines being silently dropped when an event message or parameter contained enough 3-byte UTF-8 characters to overflow the internal buffer estimate. Such content is now truncated. ([#7543](open-telemetry/opentelemetry-dotnet#7543)) * Fixed activity creation throwing when multiple tracer providers return a sampler attribute with the same key. ([#7558](open-telemetry/opentelemetry-dotnet#7558)) * Added the `otel.sdk.processor.log.processed` SDK self-observability metric. ([#7486](open-telemetry/opentelemetry-dotnet#7486)) * Added the `otel.sdk.processor.span.processed` SDK self-observability metric. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * `BatchActivityExportProcessor` and `SimpleActivityExportProcessor` no longer forward spans to the exporter once `Shutdown` has been called, and `BatchActivityExportProcessor.Shutdown` now waits for in-flight `OnEnd` calls to finish enqueueing before flushing. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * Fix logger, meter and tracer providers leaking background threads if an exception is thrown by their constructor after resource creation. ([#7615](open-telemetry/opentelemetry-dotnet#7615)) * `CircularBufferBuckets.Copy` optimized to use bulk array copies. ([#7670](open-telemetry/opentelemetry-dotnet#7670)) * Restored configured `MaxScale` after delta exponential histogram collection. ([#7671](open-telemetry/opentelemetry-dotnet#7671)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0/src/OpenTelemetry/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api v1.18.0](https://www.nuget.org/packages/OpenTelemetry.Api/1.18.0) * Avoid formatting exceptions and creating exception attributes when `RecordException` is called on a span that is not recorded. ([#7669](open-telemetry/opentelemetry-dotnet#7669)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0/src/OpenTelemetry.Api/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api.ProviderBuilderExtensions v1.18.0](https://www.nuget.org/packages/OpenTelemetry.Api.ProviderBuilderExtensions/1.18.0) No notable changes. See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0/src/OpenTelemetry.Api.ProviderBuilderExtensions/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Exporter.Console v1.18.0](https://www.nuget.org/packages/OpenTelemetry.Exporter.Console/1.18.0) * Added support for serializing attribute values that are key/value lists (`IEnumerable<KeyValuePair<string, object?>>`). These attributes will be serialized as JSON objects. ([#7015](open-telemetry/opentelemetry-dotnet#7015)) ... (truncated) ## 1.18.0-rc.1 The following changes are from the previous release [1.17.0](https://github.com/open-telemetry/opentelemetry-dotnet/releases/tag/core-1.17.0). * NuGet: [OpenTelemetry v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry/1.18.0-rc.1) * Fixed self-diagnostics log lines being silently dropped when an event message or parameter contained enough 3-byte UTF-8 characters to overflow the internal buffer estimate. Such content is now truncated. ([#7543](open-telemetry/opentelemetry-dotnet#7543)) * Fixed activity creation throwing when multiple tracer providers return a sampler attribute with the same key. ([#7558](open-telemetry/opentelemetry-dotnet#7558)) * Added the `otel.sdk.processor.log.processed` SDK self-observability metric. ([#7486](open-telemetry/opentelemetry-dotnet#7486)) * Added the `otel.sdk.processor.span.processed` SDK self-observability metric. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * `BatchActivityExportProcessor` and `SimpleActivityExportProcessor` no longer forward spans to the exporter once `Shutdown` has been called, and `BatchActivityExportProcessor.Shutdown` now waits for in-flight `OnEnd` calls to finish enqueueing before flushing. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * Fix logger, meter and tracer providers leaking background threads if an exception is thrown by their constructor after resource creation. ([#7615](open-telemetry/opentelemetry-dotnet#7615)) * `CircularBufferBuckets.Copy` optimized to use bulk array copies. ([#7670](open-telemetry/opentelemetry-dotnet#7670)) * Restored configured `MaxScale` after delta exponential histogram collection. ([#7671](open-telemetry/opentelemetry-dotnet#7671)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry.Api/1.18.0-rc.1) * Avoid formatting exceptions and creating exception attributes when `RecordException` is called on a span that is not recorded. ([#7669](open-telemetry/opentelemetry-dotnet#7669)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry.Api/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api.ProviderBuilderExtensions v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry.Api.ProviderBuilderExtensions/1.18.0-rc.1) No notable changes. See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry.Api.ProviderBuilderExtensions/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Exporter.Console v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry.Exporter.Console/1.18.0-rc.1) * Added support for serializing attribute values that are key/value lists (`IEnumerable<KeyValuePair<string, object?>>`). These attributes will be serialized as JSON objects. ([#7015](open-telemetry/opentelemetry-dotnet#7015)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry.Exporter.Console/CHANGELOG.md) for details. ... (truncated) ## 1.18.0-beta.1 The following changes are from the previous release [1.17.0-beta.1](https://github.com/open-telemetry/opentelemetry-dotnet/releases/tag/coreunstable-1.17.0-beta.1). * NuGet: [OpenTelemetry.Exporter.Prometheus.AspNetCore v1.18.0-beta.1](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.AspNetCore/1.18.0-beta.1) * Fix concurrent scrapes returning an empty response under contention. Now the exporter will return an HTTP 500 error instead. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * Waiting for concurrent scrapes to finish before collecting no longer blocks, which could stall concurrent scrapes being waited on. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * Fixed the interaction between `PrometheusAspNetCoreOptions.TranslationStrategy` and content negotiation. The configured strategy is now applied before content negotiation, instead of the negotiated escaping scheme replacing the strategy's, and the `Content-Type` header now reports the escaping scheme that was applied rather than the one that was negotiated. ([#7610](open-telemetry/opentelemetry-dotnet#7610)) * Fixed metric values and histogram bucket bounds being written with 17 significant digits instead of their shortest round-trippable representation. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) * Fixed the canonical representation used for histogram `le` and summary `quantile` label values falling back to 17 significant digits incorrectly. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) * Fixed a race where a slow scrape could return an HTTP 200 instead of 408. ([#7615](open-telemetry/opentelemetry-dotnet#7615)) * Updated OpenTelemetry core component version(s) to `1.18.0`. ([#7674](open-telemetry/opentelemetry-dotnet#7674)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/coreunstable-1.18.0-beta.1/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Exporter.Prometheus.HttpListener v1.18.0-beta.1](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.HttpListener/1.18.0-beta.1) * Fix concurrent scrapes returning an empty response under contention. Now the exporter will return an HTTP 500 error instead. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * Waiting for concurrent scrapes to finish before collecting no longer blocks, which could stall concurrent scrapes being waited on. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * A scrape which is still collecting when the listener is disposed now returns an HTTP 503 response. ([#7587](open-telemetry/opentelemetry-dotnet#7587)) * Shutting down the listener no longer waits indefinitely for its request processing loop to stop, and no longer throws if the loop faulted. ([#7587](open-telemetry/opentelemetry-dotnet#7587)) * Fixed the interaction between `PrometheusHttpListenerOptions.TranslationStrategy` and content negotiation. The configured strategy is now applied before content negotiation, instead of the negotiated escaping scheme replacing the strategy's, and the `Content-Type` header now reports the escaping scheme that was applied rather than the one that was negotiated. ([#7610](open-telemetry/opentelemetry-dotnet#7610)) * Fixed metric values and histogram bucket bounds being written with 17 significant digits instead of their shortest round-trippable representation. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) * Fixed the canonical representation used for histogram `le` and summary `quantile` label values falling back to 17 significant digits incorrectly. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) ... (truncated) Commits viewable in [compare view](open-telemetry/opentelemetry-dotnet@core-1.17.0...core-1.18.0). </details> [![Dependabot compatibility score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=OpenTelemetry.Exporter.OpenTelemetryProtocol&package-manager=nuget&previous-version=1.17.0&new-version=1.18.0)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores) Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`. [//]: # (dependabot-automerge-start) [//]: # (dependabot-automerge-end) --- <details> <summary>Dependabot commands and options</summary> <br /> You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot show <dependency name> ignore conditions` will show all of the ignore conditions of the specified dependency - `@dependabot ignore this major version` will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this minor version` will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself) </details> Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Fix duplicate sampler attribute handling

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xiang17 requested a review from a team as a code owner July 28, 2026 22:46

github-actions Bot added the pkg:OpenTelemetry Issues related to OpenTelemetry NuGet package label Jul 28, 2026

opentelemetry-pr-dashboard Bot mentioned this pull request Jul 28, 2026

Pull Request Dashboard #7539

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f081445

xiang17 mentioned this pull request Jul 28, 2026

[AzureMonitorExporter] Test rate-limited sampling with multiple tracer providers Azure/azure-sdk-for-net#61496

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cijothomas approved these changes Jul 28, 2026

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martincostello approved these changes Jul 29, 2026

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martincostello changed the title ~~Handle duplicate sampler attributes from multiple tracer providers~~ [OpenTelemetry] Handle duplicate sampler attributes Jul 29, 2026

martincostello added this pull request to the merge queue Jul 29, 2026

Merged via the queue into open-telemetry:main with commit 2e44c2a Jul 29, 2026
78 checks passed

xiang17 deleted the xiang17/duplicate-sampler-attribute branch August 5, 2026 21:35

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[OpenTelemetry] Handle duplicate sampler attributes - #7558

[OpenTelemetry] Handle duplicate sampler attributes#7558
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