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Fix context cancelling without sending COMM_QUIT for authenticated connection #1649

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minhquang4334
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@minhquang4334 minhquang4334 commented Dec 15, 2024

Description

Fix #1648

Currently, I don't know how to detect whether the connection is successful, so I added the 'authed' variable to mysqlConn. If you have a better approach, please share it with me.

Checklist

  • Code compiles correctly
  • Created tests which fail without the change (if possible)
  • All tests passing
  • Extended the README / documentation, if necessary
  • Added myself / the copyright holder to the AUTHORS file

Summary by CodeRabbit

  • New Features

    • Introduced an authentication tracking feature for database connections.
    • Enhanced error handling during connection cancellation and cleanup processes.
  • Bug Fixes

    • Improved robustness of connection management logic related to authentication state.
  • Documentation

    • Updated method signatures and field declarations for clarity on authentication handling.

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coderabbitai bot commented Dec 15, 2024

Walkthrough

The pull request introduces changes to the MySQL driver's connection management, focusing on improving context cancellation behavior for authenticated connections. A new boolean field authed is added to the mysqlConn struct to track the authentication state. The cancel method is modified to return an error and handle authenticated connections more robustly by calling Close() when appropriate. The startWatcher method is updated to log errors returned during cancellation, enhancing error handling during connection cleanup.

Changes

File Change Summary
connection.go - Added authed bool field to mysqlConn struct
- Updated cancel method signature to return an error
- Modified cancel method to check authed status before calling Close()
- Enhanced startWatcher to log cancellation errors
connector.go - Added authed bool field to mysqlConn struct
- Set authed to true after successful authentication

Sequence Diagram

sequenceDiagram
    participant Client
    participant MySQLConn
    participant MySQLServer

    Client->>MySQLConn: Initiate Connection
    MySQLConn->>MySQLServer: Authentication Request
    MySQLServer-->>MySQLConn: Authentication Response
    MySQLConn->>MySQLConn: Set authed = true
    
    alt Context Cancellation
        Client->>MySQLConn: Cancel Context
        MySQLConn->>MySQLServer: COMM_QUIT (if authed)
        MySQLConn->>MySQLConn: Close Connection
    end
Loading

Assessment against linked issues

Objective Addressed Explanation
Send COMM_QUIT for authenticated connections [#1648]
Prevent increasing Aborted_clients metric

Possibly related PRs

Suggested reviewers

  • methane

Poem

🐰 A rabbit's tale of MySQL's grace,
Where connections dance with elegant pace
authed flag waves, a signal bright
Cancelling contexts with protocol might
No clients aborted, no servers in fright! 🌟

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📜 Recent review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between c9f41c0 and 55ec77f.

📒 Files selected for processing (2)
  • connection.go (3 hunks)
  • connector.go (1 hunks)
🔇 Additional comments (5)
connector.go (1)

172-172: LGTM: Appropriate placement of authentication flag

The authed flag is set at the correct location - after successful authentication but before connection configuration. This ensures accurate tracking of the connection's authentication state.

connection.go (4)

43-43: LGTM: Well-placed struct field addition

The authed boolean field is appropriately placed within the mysqlConn struct, grouped with other connection state fields.


440-448: LGTM: Improved connection cancellation logic

The updated cancel method now properly handles both authenticated and non-authenticated connections:

  • For authenticated connections, it calls Close() which sends COMM_QUIT
  • For non-authenticated connections, it calls cleanup() directly as the server has already closed the connection
  • The error return value allows proper error propagation

This change correctly addresses the issue of sending COMM_QUIT only when appropriate.


634-636: LGTM: Enhanced error handling in connection watcher

The addition of error logging for cancel errors improves observability and will help with debugging connection issues.


440-448: Verify error handling in cancel() callers

Let's verify that all callers of the cancel() method properly handle the newly returned error.

✅ Verification successful

The previous ast-grep pattern might have failed because it was too specific. Let's try with different approaches to find cancel method calls and its implementation, along with any references to the canceled field to understand the usage pattern better.


Error handling for cancel() is properly implemented

The verification shows that:

  1. The only caller of cancel() properly handles the returned error with if err := mc.cancel(ctx.Err()); err != nil { mc.log(err) }
  2. The canceled field is consistently used throughout the codebase:
    • In error handling paths where it's checked via canceled.Value()
    • All occurrences properly handle the canceled state by returning the error
🏁 Scripts executed

The following scripts were executed for the analysis:

Script:

#!/bin/bash
# Search for all cancel() method calls
ast-grep --pattern 'mc.cancel($_)'

Length of output: 36


Script:

#!/bin/bash
# Search for cancel() method calls with more context using ripgrep
rg "\.cancel\(" -A 2 -B 2

Length of output: 203


Script:

#!/bin/bash
# Search for cancel method implementation and its usage pattern
ast-grep --pattern 'cancel($$$) {
  $$$
}'

Length of output: 44


Script:

#!/bin/bash
# Search for any direct references to the canceled field
rg "\.canceled" -A 2 -B 2

Length of output: 1162


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@minhquang4334 minhquang4334 marked this pull request as draft December 15, 2024 10:37
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Context cancelling cause close connection without sending COMM_QUIT for authenticated connection
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