[OpenTelemetry] Model changes to allow OpenTelemtry context propagation

[stankiewicz]

Changes:

• dependencies definitions to otel
• beam_fn_api.proto - traceparent and tracestate strings
• 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]

R: @sjvanrossum

[gemini-code-assist]

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]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control. If you'd like to restart, comment assign set of reviewers

[stankiewicz]

/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.

[gemini-code-assist]

The // todo radek decode w3c context comment suggests that the W3C context decoding might be incomplete or a placeholder. Please clarify the current state and future plans for this aspect of W3C context handling.

[stankiewicz]

@gemini-code-assist good bot!

[gemini-code-assist]

The comment // W3C Propagator knows what keys it wants, but this satisfies the interface for the keys method in TextMapGetter is a bit vague. While Collections.emptyList() might satisfy the interface, it would be more robust to return the actual keys that the W3C propagator expects, if known, or provide a more explicit explanation of why emptyList is sufficient and correct here.

[stankiewicz]

@gemini-code-assist good bot!

[gemini-code-assist]

Thank you for the feedback!