[Cherry-pick] fix delete nil routine (#14951)

[ck89119]

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue #14939 #15001

What this PR does / why we need it:

Fix: delete nil routine

[matrix-meow]

@ck89119 Thanks for your contributions!

Pull Request Review:

Title: [Cherry-pick] fix delete nil routine (#14951)

Body:

• The PR is categorized as a bug fix.
• It references the issue [Bug]: [date 3.12]standalone regression: tpcc 100warehouse 1000threads reported many connection timed out #14939 that it fixes.
• The purpose of the PR is to fix the "delete nil routine" routine.

Changes:

• The changes in the routine_manager.go file address the issue by modifying the deleteRoutine function in the RoutineManager struct.
• The changes aim to improve the deletion process of routines by handling nil cases more effectively.

Feedback and Suggestions:

1. Potential Issue - Nil Pointer Dereference:

   • The original code did not check if rt was nil before accessing its method getConnectionID(). This could lead to a panic if rt is nil.
   • Suggestion: Add a check for rt != nil before accessing getConnectionID() to prevent a potential nil pointer dereference.

2. Code Optimization:

   • The conditional check for rt and ok can be simplified to improve readability.
   • Suggestion: Instead of:

     if rt, ok = rm.clients[rs]; ok {

     You can directly use:

     if rt, ok := rm.clients[rs]; ok {

3. Redundant Check:

   • The code checks for ok after deleting an entry from rm.clients. This check is redundant as the entry has already been deleted.
   • Suggestion: Remove the redundant check for ok after deleting from rm.clients.

4. Consistency in Error Handling:

   • The error handling in the code can be made more consistent by handling errors uniformly throughout the function.
   • Suggestion: Ensure consistent error handling practices are followed in the function.

5. Code Comments:

   • Adding comments to explain the purpose of the code changes can improve code maintainability and readability.
   • Suggestion: Consider adding comments to describe the logic behind the changes made.

6. Testing:

   • Ensure that appropriate tests are added or updated to cover the changes made in this PR.
   • Suggestion: Add test cases to cover scenarios related to deleting routines, including nil cases.

7. Security Concern:

   • While not directly related to this PR, ensure that sensitive data or operations are handled securely throughout the codebase.
   • Suggestion: Regularly review the codebase for security vulnerabilities and follow best practices for secure coding.

By addressing the mentioned points and suggestions, the code quality, readability, and robustness can be improved. Additionally, incorporating these changes will help in maintaining a more secure and reliable codebase.