Add AlwaysRecordSampler #7877

majanjua-amzn · 2025-11-27T21:54:31Z

Background

Spec issue: open-telemetry/opentelemetry-specification#4698
Spec PR: open-telemetry/opentelemetry-specification#4699

Adding built in access to the RECORD_ONLY flag for sampling to allow for users to process spans without exporting them.

Changes

Add AlwaysRecordSampler as per spec, following aws-otel-java-instrumentation implementation
Add unit tests

Testing

Added unit tests, ./gradlew spotlessApply && ./gradlew build && ./gradlew check as per CONTRIBUTING.md guide

codecov · 2025-11-27T22:08:00Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.15%. Comparing base (18f8a13) to head (f699191).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #7877   +/-   ##
=========================================
  Coverage     90.15%   90.15%           
- Complexity     7476     7481    +5     
=========================================
  Files           836      837    +1     
  Lines         22551    22567   +16     
  Branches       2224     2225    +1     
=========================================
+ Hits          20330    20346   +16     
  Misses         1517     1517           
  Partials        704      704

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majanjua-amzn · 2025-12-02T18:14:32Z

Ready for review!

breedx-splk

Thanks for the PR. I think my biggest question is about how this will get used (if internal), but otherwise is looking good to me. There's also a merge conflict that needs to be resolved before merge.

breedx-splk · 2025-12-08T22:02:07Z

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/internal/AlwaysRecordSampler.java

+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package io.opentelemetry.sdk.trace.internal;


Is this the correct package? How are you planning for this to be consumed by users if it's internal?

Experimental SDK components is the place we've been least consistent about in terms of packaging, since sometimes the concept needs to be bundled into the SDK internals to work (i.e. ExceptionAttributeResolver). But for components which are SDK extension plugin interfaces (span processor, sampler, etc), we've been keeping them in opentelemetry-sdk-extension-incubator. Here's the relevant package for samplers: https://github.com/open-telemetry/opentelemetry-java/tree/main/sdk-extensions/incubator/src/main/java/io/opentelemetry/sdk/extension/incubator/trace/samplers

Moved the code to the incubator package

breedx-splk · 2025-12-08T22:03:18Z

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/internal/AlwaysRecordSampler.java

+    SamplingResult result =
+        rootSampler.shouldSample(parentContext, traceId, name, spanKind, attributes, parentLinks);
+    if (result.getDecision() == SamplingDecision.DROP) {
+      result = wrapResultWithRecordOnlyResult(result);


nit: no need to fall through. I think it reads marginally better to return early.

Suggested change

result = wrapResultWithRecordOnlyResult(result);

return wrapResultWithRecordOnlyResult(result);

Improved this as part of the changes for another comment: replaced the method with a delegate wrapper class instead.

...st/java/io/opentelemetry/sdk/extension/incubator/trace/samplers/AlwaysRecordSamplerTest.java

jack-berg · 2025-12-12T15:56:41Z

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/internal/AlwaysRecordSampler.java

+    if (result.getDecision() == SamplingDecision.DROP) {
+      result = wrapResultWithRecordOnlyResult(result);
+    }
+
+    return result;
+  }
+
+  @Override
+  public String getDescription() {
+    return "AlwaysRecordSampler{" + rootSampler.getDescription() + "}";
+  }
+
+  private static SamplingResult wrapResultWithRecordOnlyResult(SamplingResult result) {
+    return new SamplingResult() {
+      @Override
+      public SamplingDecision getDecision() {
+        return SamplingDecision.RECORD_ONLY;
+      }
+
+      @Override
+      public Attributes getAttributes() {
+        return result.getAttributes();
+      }
+
+      @Override
+      public TraceState getUpdatedTraceState(TraceState parentTraceState) {
+        return result.getUpdatedTraceState(parentTraceState);
+      }
+    };
+  }


Let's use a concrete class instead of an anonymous class:

Suggested change

if (result.getDecision() == SamplingDecision.DROP) {

result = wrapResultWithRecordOnlyResult(result);

}

return result;

}

@Override

public String getDescription() {

return "AlwaysRecordSampler{" + rootSampler.getDescription() + "}";

}

private static SamplingResult wrapResultWithRecordOnlyResult(SamplingResult result) {

return new SamplingResult() {

@Override

public SamplingDecision getDecision() {

return SamplingDecision.RECORD_ONLY;

}

@Override

public Attributes getAttributes() {

return result.getAttributes();

}

@Override

public TraceState getUpdatedTraceState(TraceState parentTraceState) {

return result.getUpdatedTraceState(parentTraceState);

}

};

}

if (result.getDecision() != SamplingDecision.DROP) {

return result;

}

return new RecordOnlyDelegateSamplingResult(result);

}

@Override

public String getDescription() {

return "AlwaysRecordSampler{" + rootSampler.getDescription() + "}";

}

private static class RecordOnlyDelegateSamplingResult implements SamplingResult {

private final SamplingResult delegate;

private RecordOnlyDelegateSamplingResult(SamplingResult delegate) {this.delegate = delegate;}

@Override

public SamplingDecision getDecision() {

return SamplingDecision.RECORD_ONLY;

}

@Override

public Attributes getAttributes() {

return delegate.getAttributes();

}

@Override

public TraceState getUpdatedTraceState(TraceState parentTraceState) {

return delegate.getUpdatedTraceState(parentTraceState);

}

}

jack-berg · 2025-12-12T15:57:01Z

sdk/trace/src/test/java/io/opentelemetry/sdk/trace/internal/AlwaysRecordSamplerTest.java

+  }
+
+  @Test
+  void testGetDescription() {


remote test prefix on all these

jack-berg · 2025-12-12T15:58:59Z

sdk/trace/src/test/java/io/opentelemetry/sdk/trace/internal/AlwaysRecordSamplerTest.java

+  }
+
+  @Test
+  void testRecordAndSampleSamplingDecision() {


Can use a org.junit.jupiter.params.ParameterizedTest test to improve readability.

jack-berg

Couple small things that need adjusting. Thanks for working on this!

breedx-splk · 2026-01-05T23:36:53Z

bump @majanjua-amzn in case you can circle back to this now in the new year. 😉 Thanks again!

majanjua-amzn · 2026-01-21T00:50:49Z

Ready for review again! Apologies for the delay, cc @jack-berg since you marked it as requested change, thanks in advance

majanjua-amzn requested a review from a team as a code owner November 27, 2025 21:54

majanjua-amzn force-pushed the main branch from cdad898 to 827cecf Compare November 27, 2025 21:55

majanjua-amzn mentioned this pull request Nov 28, 2025

Add spec for AlwaysRecord sampler open-telemetry/opentelemetry-specification#4699

Merged

5 tasks

breedx-splk approved these changes Dec 8, 2025

View reviewed changes

jack-berg reviewed Dec 12, 2025

View reviewed changes

jack-berg requested changes Dec 12, 2025

View reviewed changes

jack-berg mentioned this pull request Dec 19, 2025

Add alwaysRecord Sampler #4602

Open

jack-berg linked an issue Dec 19, 2025 that may be closed by this pull request

Add alwaysRecord Sampler #4602

Open

majanjua-amzn force-pushed the main branch 2 times, most recently from 7d9e351 to 3dd5a79 Compare January 21, 2026 00:05

Add AlwaysRecordSampler

f699191

majanjua-amzn force-pushed the main branch from 3dd5a79 to f699191 Compare January 21, 2026 00:07

majanjua-amzn requested a review from jack-berg January 21, 2026 00:15

	result = wrapResultWithRecordOnlyResult(result);
	return wrapResultWithRecordOnlyResult(result);

Add AlwaysRecordSampler #7877

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Add AlwaysRecordSampler #7877

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breedx-splk commented Jan 5, 2026

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majanjua-amzn commented Jan 21, 2026

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