fix: Limit storage connection lifetime in worker

[sitaowang1998]

Description

Worker keeps a storage connection object for the whole schedule task request and task execution. This pr limits the lifetime of storage connection to minimum for getting scheduler address only, and release the connection asap.

Checklist

• The PR satisfies the contribution guidelines.
• This is a breaking change and that has been indicated in the PR title, OR this isn't a
  breaking change.
• Necessary docs have been updated, OR no docs need to be updated.

Validation performed

• GitHub workflows pass
• Unit tests pass in dev container
• Integration tests pass in dev container

Summary by CodeRabbit

• Refactor
  • Improved connection handling and error management for background task processing, enhancing reliability and resource management. These updates strengthen system stability while maintaining the overall user experience.

[coderabbitai]

Walkthrough

The changes refactor the get_next_task method in the WorkerClient class to encapsulate the connection handling logic within its own scope, thereby aiding RAII management of the MySQL connection. Additionally, the type for the connection result is updated to use the core namespace instead of spider::core. The error handling and subsequent checks for active schedulers remain unchanged. Similarly, the task_loop function in worker.cpp also undergoes a restructuring of connection handling and error checking, with the connection logic now encapsulated within a scoped block.

Changes

File(s)	Change Summary
src/spider/worker/WorkerClient.cpp	Refactored the connection logic in get_next_task by introducing a new scope for RAII management; updated the variant's namespace from spider::core to core.
src/spider/worker/worker.cpp	Restructured the connection handling in task_loop by encapsulating it within a new scope; moved error handling for task fetching into this scope; declared optional_args_buffers earlier in the function.

Sequence Diagram(s)

sequenceDiagram
    autonumber
    participant WC as WorkerClient
    participant Scope as RAII Scope
    participant DB as Database
    participant Logger as Logger

    WC ->> Scope: Enter connection scope block
    Scope ->> DB: Establish MySQL connection
    DB -->> Scope: Return connection result (success or error)
    alt Connection Error
       Scope ->> Logger: Log error
       Scope -->> WC: Return StorageErr
    else Successful Connection
       Scope -->> WC: Return MySqlConnection
       WC ->> WC: Check active scheduler and process task
    end

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📥 Commits

Reviewing files that changed from the base of the PR and between fe17823 and 9e10cff.

📒 Files selected for processing (1)

• src/spider/worker/worker.cpp (2 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (3)

• GitHub Check: non-storage-unit-tests (ubuntu-24.04)
• GitHub Check: lint
• GitHub Check: non-storage-unit-tests (ubuntu-22.04)

🔇 Additional comments (2)

src/spider/worker/worker.cpp (2)

240-271: RAII enhancement effectively reduces storage connection lifetime

The implementation now appropriately encapsulates the MySQL connection within a limited scope, ensuring it's promptly released after fetching task details and argument processing. This change aligns perfectly with the PR's objective of reducing connection lifetime to the minimum necessary duration.

This approach:

• Ensures proper resource management via RAII
• Reduces resource contention by releasing connections earlier
• Improves resilience against connection pool exhaustion
• Maintains identical business logic while improving resource usage

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288-297: Same RAII pattern applied consistently for result processing

This second instance of connection management follows the same pattern as the previous one, maintaining consistency in the codebase. The connection is created only when needed for task completion reporting and immediately goes out of scope when the operations are complete.

✨ Finishing Touches

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