Adding Dataflow MDC Sample

[ebeltran-g]

Description

Adding a new Snippet code to use it as reference in the public doc. This will replace existing example which is only in the documentation
https://docs.cloud.google.com/dataflow/docs/guides/logging#df-integration

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

Checklist

• I have followed Sample Format Guide
• pom.xml parent set to latest shared-configuration
• Appropriate changes to README are included in PR
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Tests pass: mvn clean verify required
• Lint passes: mvn -P lint checkstyle:check required
• Static Analysis: mvn -P lint clean compile pmd:cpd-check spotbugs:check advisory only
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[gemini-code-assist]

Summary of Changes

Hello @ebeltran-g, 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 introduces a new Dataflow sample that demonstrates the use of Mapped Diagnostic Context (MDC) for enhanced logging within a Dataflow pipeline. The sample reads messages from a Pub/Sub subscription and uses MDC to include the message ID in log statements, providing a clearer context for each log entry. This new snippet will be used to update the public documentation, offering a practical and up-to-date reference for Dataflow users.

Highlights

• New Dataflow MDC Sample: A new Dataflow snippet, MdcSample.java, has been added to demonstrate the use of Mapped Diagnostic Context (MDC) for logging within a Dataflow pipeline.
• Documentation Reference: This new sample is intended to replace an existing example in the public Dataflow documentation, providing an updated and runnable reference for users.
• MDC Integration: The sample illustrates how to read messages from a Pub/Sub subscription and use MDC.putCloseable to associate the Pub/Sub message ID with log statements, enhancing log context.

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[gemini-code-assist]

Code Review

This pull request adds a new Dataflow snippet demonstrating how to use Mapped Diagnostic Context (MDC) for enhanced logging. The example is clear and serves its purpose well. I've provided a few suggestions to improve the code's robustness, error handling, and adherence to best practices, particularly concerning character encoding, logging efficiency, exception management, and pipeline execution.