fix(Spanner): Added read-only validation for Mysql shards. This does not validate the user authority.

[pratickchokhani]

No description provided.

[gemini-code-assist]

Summary of Changes

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This pull request enhances the robustness of the Spanner-to-sourcedb data pipeline by adding a critical validation for MySQL shard connections. It ensures that the application does not attempt to establish connections to MySQL instances configured as read-only, thereby preventing potential data integrity issues or unexpected behavior during migration processes. This change improves the reliability of database interactions without affecting user authority.

Highlights

• MySQL Read-Only Validation: Implemented a new validation step to check if a MySQL shard is in read-only mode during connection pool initialization.
• Connection Rejection: Connections to MySQL shards detected as read-only will now be rejected with an SQLException, preventing write operations on read-only instances.
• New Utility Method: Introduced a private method, validateMysqlHikariConnection, to encapsulate the logic for checking the @@global.read_only system variable.

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[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 52.47%. Comparing base (b1aa685) to head (dc26602).

Files with missing lines	Patch %	Lines
...lates/dbutils/connection/JdbcConnectionHelper.java	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3658      +/-   ##
============================================
- Coverage     52.49%   52.47%   -0.02%     
- Complexity     5815     5817       +2     
============================================
  Files          1062     1062              
  Lines         64136    64145       +9     
  Branches       7089     7090       +1     
============================================
- Hits          33668    33662       -6     
- Misses        28189    28201      +12     
- Partials       2279     2282       +3     

Components	Coverage Δ
spanner-templates	72.13% <88.88%> (-0.05%)	⬇️
spanner-import-export	68.77% <ø> (-0.13%)	⬇️
spanner-live-forward-migration	80.87% <ø> (ø)
spanner-live-reverse-replication	77.55% <88.88%> (-0.03%)	⬇️
spanner-bulk-migration	89.32% <ø> (ø)
gcs-spanner-dv	85.75% <ø> (ø)

Files with missing lines	Coverage Δ
...lates/dbutils/connection/JdbcConnectionHelper.java	83.07% <88.88%> (-4.43%)	⬇️

... and 5 files with indirect coverage changes

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[manitgupta]

Is this class specific to MySQL? How does this work for PG and other JDBC sources?

[manitgupta]

Is it possible to add some helpful debugging data about the shard which was in read-only mode? The current error does not tell the user where the error is occurring?

[manitgupta]

Nit: Lets use the same naming convention as the existing tests. (camelCase?)