Seperated live migration 2

[bharadwaj-aditya]

This is a part of the effort to separate source specific logic from the standard template logic for spanner migrations.
PR1 - #3942
PR 2 - Move source specific logic into connectors. This does not increase test coverage for any pre-existing code.

Following PRs will move the constants and bump up the test coverage.

[codecov]

Codecov Report

❌ Patch coverage is 85.36585% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.04%. Comparing base (3d09e7b) to head (a307d1b).

Files with missing lines	Patch %	Lines
...ort/v2/templates/SpannerTransactionWriterDoFn.java	77.77%	3 Missing and 1 partial ⚠️
...ce/DatastreamToSpannerSourceConnectorRegistry.java	85.18%	2 Missing and 2 partials ⚠️
...eam/source/oracle/OracleDsToSpSourceConnector.java	77.77%	2 Missing ⚠️
...ce/postgresql/PostgresqlDsToSpSourceConnector.java	77.77%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##               main    #3947       +/-   ##
=============================================
+ Coverage     38.10%   62.04%   +23.94%     
- Complexity      512     3102     +2590     
=============================================
  Files           195      545      +350     
  Lines         11745    32762    +21017     
  Branches       1173     3605     +2432     
=============================================
+ Hits           4475    20326    +15851     
- Misses         6908    11367     +4459     
- Partials        362     1069      +707     

Components	Coverage Δ
spanner-templates	88.07% <85.36%> (∅)
spanner-import-export	∅ <ø> (∅)
spanner-live-forward-migration	89.76% <85.36%> (∅)
spanner-live-reverse-replication	83.27% <ø> (∅)
spanner-bulk-migration	92.54% <ø> (∅)
gcs-spanner-dv	90.34% <ø> (∅)

Files with missing lines	Coverage Δ
...oud/teleport/v2/templates/DataStreamToSpanner.java	94.61% <100.00%> (ø)
...tastream/source/mysql/MySqlChangeEventContext.java	100.00% <ø> (ø)
...astream/source/mysql/MySqlChangeEventSequence.java	92.18% <ø> (ø)
...tream/source/mysql/MySqlDsToSpSourceConnector.java	100.00% <100.00%> (ø)
...stream/source/oracle/OracleChangeEventContext.java	100.00% <ø> (ø)
...tream/source/oracle/OracleChangeEventSequence.java	54.54% <ø> (ø)
...source/postgresql/PostgresChangeEventSequence.java	62.26% <ø> (ø)
...eport/v2/templates/spanner/ShadowTableCreator.java	97.72% <100.00%> (ø)
...eam/source/oracle/OracleDsToSpSourceConnector.java	77.77% <77.77%> (ø)
...ce/postgresql/PostgresqlDsToSpSourceConnector.java	77.77% <77.77%> (ø)
... and 2 more

... and 393 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[gemini-code-assist]

Summary of Changes

Hello, 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 continues the effort to decouple source-specific logic from the standard migration template. By introducing a registry of source connectors, the codebase becomes more modular and easier to extend for future source types. The changes improve maintainability by centralizing source-specific behaviors and removing redundant factory classes.

Highlights

• Refactoring to Source Connectors: Introduced the ISourceConnector interface and SourceConnectorRegistry to encapsulate source-specific logic, replacing hardcoded checks for MySQL, Oracle, and PostgreSQL.
• Code Cleanup: Removed the legacy ChangeEventContextFactory and ChangeEventSequenceFactory classes in favor of the new connector-based registry pattern.
• Validation Improvements: Added explicit source type validation in SpannerTransactionWriterDoFn to ensure change events match the expected source configuration.

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 the 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 counterproductive. You can react with 👍 and 👎 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.

Footnotes

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. ↩

[gemini-code-assist]

Code Review

This pull request refactors the Datastream to Spanner template to decouple source-specific logic by introducing the ISourceConnector interface and a SourceConnectorRegistry. This replaces the static factory classes (ChangeEventContextFactory and ChangeEventSequenceFactory) with dynamic connector lookups, improving extensibility for MySQL, PostgreSQL, and Oracle. A review comment points out a discrepancy in SourceConnectorRegistry where the Javadoc claims to use SPI for discovering connectors, but the implementation statically registers them instead.