MySQL: Track session-specific system variables changes

[wazir-ahmed]

• Configure session_track_system_variables and session_track_state_change in all backend connections.
• Utilize notifications from backend servers to capture system variable changes that cannot be handled by MySQL_Set_Stmt_Parser
• Update both client and server variable maps based on backend responses.

[gemini-code-assist]

Summary of Changes

Hello @wazir-ahmed, 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 comprehensive support for tracking session-specific system variable changes within MySQL backend connections. It establishes a robust mechanism to configure the necessary session tracking settings, process notifications from the backend when variables change, and synchronize these changes across the internal client and server variable states. This enhancement improves the accuracy of ProxySQL's understanding of the backend session state, particularly for variables that are not easily parsed from SQL statements.

Highlights

• Session Variable Tracking Configuration: Implemented logic to configure session_track_system_variables and session_track_state_change on all backend connections to enable server-side tracking of session variable changes.
• Backend Notification Processing: Added mechanisms to utilize notifications from backend servers to capture system variable changes that cannot be reliably handled by statement parsing alone.
• Variable Map Synchronization: Ensured that both client and server internal variable maps are accurately updated based on the session variable changes communicated from the backend responses, maintaining state consistency.

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[gemini-code-assist]

Code Review

This pull request introduces tracking for session-specific system variables in MySQL by leveraging session_track_system_variables and session_track_state_change. The changes include new handlers and logic to set and process these variables, ensuring that changes are captured and synchronized between the client and server. My review focuses on improving code safety, clarity, and performance in the new implementations. I've suggested using safer string comparison functions, reducing variable scopes for better readability, and making minor performance optimizations in string handling. I also pointed out a commented-out line that should be removed.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud