[OpenTelemetry] Model changes to allow OpenTelemtry context propagation #36962

stankiewicz · 2025-12-02T13:46:44Z

Changes:

dependencies definitions to otel
WindowedValue interface change to expose context for propagation - context is not read by user
changes are behind external_metadata experiment

Next PRs:

propagation to windmill sink
reading from windmill reader
enabling default otel implementation for dataflow runner (v1 with propagation, v2 no propagation yet)

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stankiewicz · 2025-12-02T13:47:06Z

R: @sjvanrossum

gemini-code-assist · 2025-12-02T13:47:13Z

Summary of Changes

Hello @stankiewicz, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request lays the foundational groundwork for integrating OpenTelemetry context propagation within Apache Beam. It involves updating OpenTelemetry dependencies, extending the internal data model (beam_fn_api.proto and WindowedValue interface) to carry trace context information, and implementing the necessary serialization/deserialization logic. These changes are part of an ongoing effort to enhance observability by enabling end-to-end distributed tracing across Beam pipelines, currently under an experimental flag.

Highlights

OpenTelemetry Dependency Updates: Updated and added several OpenTelemetry dependencies in BeamModulePlugin.groovy and various build.gradle files to support OpenTelemetry context propagation.
Protocol Buffer Extension for Trace Context: Modified beam_fn_api.proto to include traceparent and tracestate fields within the ElementMetadata message, enabling the serialization of W3C Trace Context.
WindowedValue Interface Enhancement: Extended the WindowedValue interface and its implementations to include a getContext() method, allowing the OpenTelemetry Context to be associated with and propagated alongside data elements.
OpenTelemetry Context Serialization: Introduced OpenTelemetryContextSerializer to handle the encoding and decoding of OpenTelemetry Context objects into and from the ElementMetadata of WindowedValue using the W3C Trace Context Propagator.
Experimental Feature: These changes are implemented behind an external_metadata experiment flag, indicating an incremental rollout and testing approach.

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github-actions · 2025-12-02T13:48:48Z

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stankiewicz · 2025-12-02T15:15:24Z

/gemini review

gemini-code-assist

Code Review

The pull request effectively integrates OpenTelemetry context propagation into Apache Beam's core data structures and serialization mechanisms. This foundational change is well-implemented across various files, ensuring the Context is carried alongside WindowedValue elements. Key aspects include updating dependencies, extending the protocol buffer schema for traceparent and tracestate, modifying core WindowedValue interfaces and implementations to include the Context, and implementing robust serialization/deserialization logic via OpenTelemetryContextSerializer. The addition of a test case in WindowedValueTest.java validates the new functionality. The use of null for getContext() in specific overrides is consistent with the stated scope that the context is not yet consumed by users. Overall, this is a solid and necessary step towards comprehensive OpenTelemetry integration.

sdks/java/core/src/main/java/org/apache/beam/sdk/values/WindowedValues.java

…tadata proto

stankiewicz · 2025-12-08T14:51:50Z

...ud-platform-core/src/test/java/org/apache/beam/sdk/extensions/gcp/GcpCoreApiSurfaceTest.java

            classesInPackage("com.fasterxml.jackson.annotation"),
            classesInPackage("com.google.cloud.hadoop.gcsio"),
            classesInPackage("com.google.common.collect"), // Via gcs-connector ReadOptions builder
+            classesInPackage("io.opentelemetry"), // open telemetry


@kennknowles I had to at this as we are exposing otel context in

interface org.apache.beam.sdk.values.WindowedValue interface org.apache.beam.sdk.values.OutputBuilder interface org.apache.beam.sdk.transforms.DoFn$OutputReceiver

This is fine. I actually think this test code-rotted some time ago, and also its purpose is somewhat obsolete: Before we released "vendor" versions of Guava and Calcite and other things, we relocated and included them in the built jars dynamically - so our codebase looked like it linked to the normal version, but during jar assembly it was relocated to the vendor namespace. So we accidentally could ship something with an API that could never be used. This test was to make sure we didn't do that. Now that we (mostly) vendor things, it is less important. We probably still have some uses of dynamic relocation, but it isn't "everything/everywhere" like it used to be.

(I had a philosophy, which turns out to be a PITA, that we should relocate everything except for allowlisted API surface classes, to keep dependencies to only actual public deps. This is slow, causes massive bloat, and IDEs do not understand it. I still like the idea that "implementation detail" dependencies do not impact users but it needs language and runtime support, not hacking in the build system - the "right" way in Java is probably classloaders, ugh)

kennknowles · 2025-12-08T16:09:09Z

...ud-platform-core/src/test/java/org/apache/beam/sdk/extensions/gcp/GcpCoreApiSurfaceTest.java

            classesInPackage("com.fasterxml.jackson.annotation"),
            classesInPackage("com.google.cloud.hadoop.gcsio"),
            classesInPackage("com.google.common.collect"), // Via gcs-connector ReadOptions builder
+            classesInPackage("io.opentelemetry"), // open telemetry


This is fine. I actually think this test code-rotted some time ago, and also its purpose is somewhat obsolete: Before we released "vendor" versions of Guava and Calcite and other things, we relocated and included them in the built jars dynamically - so our codebase looked like it linked to the normal version, but during jar assembly it was relocated to the vendor namespace. So we accidentally could ship something with an API that could never be used. This test was to make sure we didn't do that. Now that we (mostly) vendor things, it is less important. We probably still have some uses of dynamic relocation, but it isn't "everything/everywhere" like it used to be.

(I had a philosophy, which turns out to be a PITA, that we should relocate everything except for allowlisted API surface classes, to keep dependencies to only actual public deps. This is slow, causes massive bloat, and IDEs do not understand it. I still like the idea that "implementation detail" dependencies do not impact users but it needs language and runtime support, not hacking in the build system - the "right" way in Java is probably classloaders, ugh)

kennknowles · 2025-12-08T16:10:13Z

buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy

-        opentelemetry_api                           : "io.opentelemetry:opentelemetry-api", // google_cloud_platform_libraries_bom sets version
+        opentelemetry_api                           : "io.opentelemetry:opentelemetry-api:$opentelemetry_version",
        opentelemetry_bom                           : "io.opentelemetry:opentelemetry-bom-alpha:$opentelemetry_version-alpha", // alpha required by extensions
+        opentelemetry_context                       : "io.opentelemetry:opentelemetry-context:$opentelemetry_version",


Will this change conflict with the GCP BOM? @suztomo do you think this is fine? We might just need to check them together manually.

kennknowles · 2025-12-08T16:11:59Z

...e-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/BatchViewOverrides.java

    }

+    @Override
+    public @Nullable Context getContext() {


getContext is pretty generic, even though it is accurate in this context (pun intended). Perhaps getOpenTelemetryContext even though it is longer it'll be more readable.

kennknowles · 2025-12-08T16:13:46Z

sdks/java/core/src/main/java/org/apache/beam/sdk/values/WindowedValues.java

-        .setPaneInfo(template.getPaneInfo());
+        .setPaneInfo(template.getPaneInfo())
+        .setContext(template.getContext())
+        .setCausedByDrain(template.causedByDrain())


All this propagation of other fields would be valuable to commit separately for code history. Perhaps jj split these to other PRs, or make them tiny commits in this PR.

kennknowles · 2025-12-08T16:15:33Z

sdks/java/core/src/main/java/org/apache/beam/sdk/values/WindowedValues.java

    @Override
    public WindowedValue<T> decode(InputStream inStream) throws CoderException, IOException {
-      return decode(inStream, Context.NESTED);
+      return decode(inStream, org.apache.beam.sdk.coders.Coder.Context.NESTED);


Should be able to be Coder.Context if you want.

kennknowles · 2025-12-08T16:25:58Z

sdks/java/core/src/main/java/org/apache/beam/sdk/values/WindowedValues.java

+    }
+
+    public static Context read(BeamFnApi.Elements.ElementMetadata from) {
+      return W3CTraceContextPropagator.getInstance().extract(Context.root(), from, GETTER);


OK... this way of doing things matches https://opentelemetry.io/docs/specs/otel/context/api-propagators/

But it does seem like a complicated way of doing the equivalent of

W3TraceContextPropagator.getInstance().setTracestate(elementMetadata.getTracestate()); W3TraceContextPropagator.getInstance().setTraceparent(elementMetadata.getTraceparent());

and

elementMetadataBuilder.setTracestate(W3TraceContextPropagator.getInstance().getTracestate()); elementMetadataBuilder.setTraceparent(W3TraceContextPropagator.getInstance().getTraceparent());

Other nit: did we not agree that the ElementMetadata object should be only implementation detail? This class and everything should be private since it is just for encoding/decoding utility. But potentially also you want to do the SETTER on an Builder and the GETTER on a WindowedValue. If it is implementation detail, hidden, then I don't care that much, but if it is public then we have to be careful about what classes we use.

kennknowles · 2025-12-08T16:29:34Z

sdks/java/core/src/main/java/org/apache/beam/sdk/values/WindowedValues.java

    }
  }

+  public static class OpenTelemetryContextSerializer {


private? Possibly package level access (maybe it is just @VisibleForTesting? I didn't audit the whole PR...

github-actions bot added java build model runners spark dataflow labels Dec 2, 2025

gemini-code-assist bot reviewed Dec 2, 2025

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stankiewicz force-pushed the model branch from 65e3fdd to 7be5980 Compare December 2, 2025 15:37

[OpenTelemetry] Add traceparent and tracestate to extended element me…

437cd3c

…tadata proto

stankiewicz force-pushed the model branch from 7be5980 to 69f9591 Compare December 5, 2025 21:46

github-actions bot removed the model label Dec 5, 2025

stankiewicz force-pushed the model branch from 69f9591 to 9c7ed81 Compare December 6, 2025 10:05

Model changes to allow OpenTelemtry context propagation

43f92ec

stankiewicz force-pushed the model branch from 9c7ed81 to 43f92ec Compare December 8, 2025 14:40

github-actions bot added extensions gcp labels Dec 8, 2025

stankiewicz commented Dec 8, 2025

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kennknowles reviewed Dec 8, 2025

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[OpenTelemetry] Model changes to allow OpenTelemtry context propagation #36962

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stankiewicz commented Dec 2, 2025 •

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