[OpenTelemetry] Model changes to allow OpenTelemtry context propagation

[stankiewicz]

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)

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• [ ] Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• [ ] Update CHANGES.md with noteworthy changes.
• [ ] If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README to see a list of phrases to trigger workflows.

[stankiewicz]

R: @sjvanrossum

[gemini-code-assist[bot]]

Summary of Changes

Hello @stankiewicz, I'm Gemini Code Assist[^1]! 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.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with :thumbsup: and :thumbsdown: on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

[^1]: Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution.

[github-actions[bot]]

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