[bug] proxy: session does not transfer after COM_STMT_CLOSE.

[volgariver6]

User description

What type of PR is this?

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

Which issue(s) this PR fixes:

issue https://github.com/matrixorigin/MO-Cloud/issues/4022

What this PR does / why we need it:

there is no response from server after client send a COM_STMT_CLOSE cmd,
which will cause the session cannot be transferred forever. So ignore the
send time when client send a COM_STMT_CLOSE cmd.

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PR Type

Bug fix, Tests

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Description

• Fixed a bug where sessions did not transfer after a COM_STMT_CLOSE command by ignoring the send time for such commands.
• Introduced a buffer variable tempBuf to improve buffer handling.
• Added utility functions isEmptyPacket and isDeallocatePacket to identify packet types.
• Updated logic to conditionally set lastCmdTime based on packet type.
• Added unit tests for the new utility functions to ensure correct packet type identification.

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Changes walkthrough 📝

	Relevant files
Bug fix	tunnel.go Improve session handling and command time management          pkg/proxy/tunnel.go Introduced tempBuf to hold buffer data for processing. Added checks for empty and deallocate packets. Updated logic to set lastCmdTime conditionally. +14/-7
Enhancement	util.go Add utility functions for packet type checking                      pkg/proxy/util.go Added isEmptyPacket function to check for empty packets. Added isDeallocatePacket function to identify deallocate packets. +15/-0
Tests	util_test.go Add tests for packet utility functions                                      pkg/proxy/util_test.go Added tests for isDeallocatePacket function. Added tests for isEmptyPacket function. +27/-0

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PR Reviewer Guide 🔍

⏱️ Estimated effort to review: 3 🔵🔵🔵⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ Key issues to review Potential Race Condition The p.mu.lastCmdTime is being set without acquiring a lock, which could lead to a race condition if multiple goroutines access this field concurrently. Error Handling The function isEmptyPacket is called twice in the conditional statement. This could be optimized to improve readability and performance.

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PR Code Suggestions ✨

Category	Suggestion	Score
Maintainability	Extract pipe handling logic into separate functions Consider extracting the logic for handling the server-to-client pipe into a separate function to improve code readability and maintainability. pkg/proxy/tunnel.go [559-597] if p.name == pipeServerToClient { + handleServerToClientPipe(p, tempBuf, peer) +} else { + handleClientToServerPipe(p, tempBuf) +} + +// ... (define the new functions below) + +func handleServerToClientPipe(p *pipe, tempBuf []byte, peer *pipe) { var currSeq int16 // issue#16042 if len(tempBuf) > 3 { currSeq = int16(tempBuf[3]) } - // last sequence id is 255 and current sequence id is 0, the - // sequence ID is rotated, in which case, we do NOT allow to - ... - if !p.mu.inTxn && p.tun.transferIntent.Load() && !rotated { - peer.wg.Add(1) - p.transferred = true - } - if len(tempBuf) > 3 { - lastSeq = int16(tempBuf[3]) - } - p.mu.lastCmdTime = time.Now() -} else { + // ... (rest of the server-to-client logic) +} + +func handleClientToServerPipe(p *pipe, tempBuf []byte) { if isEmptyPacket(tempBuf) { p.logger.Warn("there comes an empty packet from client") } if !isEmptyPacket(tempBuf) && !isDeallocatePacket(tempBuf) { p.mu.lastCmdTime = time.Now() } } Suggestion importance[1-10]: 8 Why: Extracting the logic into separate functions significantly improves code readability and maintainability by organizing the code into smaller, more manageable pieces.	8
Best practice	Move variable declaration closer to its first usage Consider moving the tempBuf declaration closer to where it's first used to improve code readability and reduce the scope of the variable. pkg/proxy/tunnel.go [556-564] -tempBuf := p.src.readAvailBuf() // set txn status and cmd time within the mutex together. // only server->client pipe need to set the txn status. if p.name == pipeServerToClient { var currSeq int16 + tempBuf := p.src.readAvailBuf() // issue#16042 if len(tempBuf) > 3 { currSeq = int16(tempBuf[3]) } Apply this suggestion Suggestion importance[1-10]: 7 Why: Moving the tempBuf declaration closer to its first use can improve readability and reduce the variable's scope, which is a good practice for maintainability, but it is not crucial.	7
Enhancement	Simplify function by combining conditions into a single return statement The isEmptyPacket function can be simplified to a single return statement, making it more concise and easier to read. pkg/proxy/util.go [101-106] func isEmptyPacket(p []byte) bool { - if p == nil || len(p) == 0 { - return true - } - return false + return p == nil || len(p) == 0 } Apply this suggestion Suggestion importance[1-10]: 7 Why: Simplifying the function to a single return statement makes the code more concise and easier to read, which is a minor but beneficial enhancement.	7
	Improve function documentation with more detailed explanation The comment for isDeallocatePacket function is incomplete. Consider providing a more descriptive comment explaining what a MySQL deallocate packet is and how it's identified. pkg/proxy/util.go [108-114] -// isDeallocatePacket returns true if []byte is a MySQL +// isDeallocatePacket returns true if the given byte slice represents a MySQL +// COM_STMT_CLOSE packet, which is used to deallocate a prepared statement. +// The packet is identified by having a length of at least 5 bytes and +// the 5th byte (index 4) being 0x19 (25 in decimal). func isDeallocatePacket(p []byte) bool { if len(p) > 4 && p[4] == 0x19 { return true } return false } Apply this suggestion Suggestion importance[1-10]: 6 Why: Improving the documentation with a more detailed explanation enhances code clarity and helps future developers understand the function's purpose, though it is not critical.	6