fix: add exception handling to Redis subscription listener for resource cleanup

[NeatGuyCoding]

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Summary

fix: add exception handling to Redis subscription listener for resource cleanup

Screenshots

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Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[gemini-code-assist]

Summary of Changes

Hello @NeatGuyCoding, 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 enhances the stability of the Redis broadcast channel subscription mechanism by introducing comprehensive exception handling. It guarantees that Redis PubSub resources are properly unsubscribed and closed, even if unforeseen errors occur during message reception or processing, thereby preventing potential resource leaks and improving the overall resilience of the system.

Highlights

• Robust Error Handling: Implemented a try...except...finally block around the Redis subscription listener's main loop to catch and log unexpected exceptions during message processing.
• Guaranteed Resource Cleanup: Ensured that _unsubscribe() and pubsub.close() are always called in the finally block, preventing resource leaks even if errors occur.
• Improved Logging: Added detailed logging for exceptions within the listener thread and for the successful or failed cleanup of Redis resources.

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[gemini-code-assist]

Code Review

This pull request introduces crucial exception handling to the Redis subscription listener, ensuring robust resource cleanup even when errors occur. The use of a try...finally block around the listener loop and individual try...except blocks for cleanup operations is a solid approach to improve reliability. I have one suggestion to simplify the cleanup logic slightly for better readability.

[gemini-code-assist]

The nested finally block is not necessary here. Execution will proceed to the line after the try...except block regardless of whether an exception was caught. You can simplify the code and improve readability by removing the finally statement and un-indenting self._pubsub = None.

            try:
                pubsub.close()
                _logger.debug("%s PubSub closed for topic %s", self._get_subscription_type().title(), self._topic)
            except Exception as e:
                _logger.warning(
                    "Error closing PubSub for %s channel %s: %s",
                    self._get_subscription_type(),
                    self._topic,
                    e,
                )
            self._pubsub = None

[Copilot]

Pull request overview

This PR adds comprehensive exception handling and resource cleanup to the Redis subscription listener to prevent resource leaks when errors occur during message processing or cleanup operations.

Key changes:

• Wraps the main message processing loop in a try-except block to catch and log unexpected errors
• Moves resource cleanup operations (unsubscribe and pubsub close) into a finally block to ensure they always execute
• Wraps individual cleanup operations in separate try-except blocks to prevent one failing cleanup from blocking others
• Uses a nested finally block to guarantee _pubsub is always set to None, even if cleanup operations fail

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[Copilot]

Inconsistent terminology in log message. This message uses "for topic %s" while all other log messages in this file use "channel" (e.g., lines 108, 115, 125: "for channel %s").

Consider changing to:

_logger.debug("%s PubSub closed for channel %s", self._get_subscription_type().title(), self._topic)

This would make the terminology consistent throughout the file.

Suggested change

	_logger.debug("%s PubSub closed for topic %s", self._get_subscription_type().title(), self._topic)
	_logger.debug("%s PubSub closed for channel %s", self._get_subscription_type().title(), self._topic)