added SessionResetter into driver_conn optional interfaces

[siddhesh-tamhanekar]

Links

N/A

Details

Problem

The nrmysql driver in newrelic/go-agent does not properly handle connection reuse in case of last query was errored when MySQL closes an idle connection and application try to reuse it, This leads to a "commands out of sync" error when the same connection is used again.

Steps to Reproduce
The following test program demonstrates the issue:

package main

import (
	"database/sql"
	"fmt"
	"time"

	_ "github.com/go-sql-driver/mysql"
	_ "github.com/newrelic/go-agent/v3/integrations/nrmysql"
)

func main() {
	mysqlConnString := fmt.Sprintf("%s:%s@tcp(%s:%s)/%s?charset=utf8mb4&parseTime=True&loc=Local", "user", "pass", "127.0.0.1", "3306", "db_name")
	mdb, err := sql.Open("nrmysql", mysqlConnString)
	fmt.Println("mysql open error:", err)

	mdb.Ping()
	fmt.Println("ping error:", err)

	// This query will fail
	q("select * from table_not_exists", mdb)

	// Simulate MySQL closing the connection after idle time (e.g., 10s)
	time.Sleep(time.Second * 12)

	// This will result in "commands out of sync" error
	q("select * from users", mdb)
}

func q(sql string, mdb *sql.DB) {
	rows, err := mdb.Query(sql)
	if err == nil {
		cols, _ := rows.Columns()
		columns := make([]interface{}, len(cols))
		columnPointers := make([]interface{}, len(cols))
		for i := range columns {
			columnPointers[i] = &columns[i]
		}
		rows.Next()
		scanErr := rows.Scan(columnPointers...)
		fmt.Println("mysql query error:", err, scanErr, columns)
	} else {
		fmt.Println("mysql query error:", err)
	}
}

Root Cause

The repository provides an SQL driver that implements various sql package interfaces. One of these interfaces is driver.SessionResetter, which is already implemented in sql_driver.go. However, the optionalMethodsConn type in sql_driver_optional_methods.go did not support driver.SessionResetter.

Solution

• Updated internal/tools/interface-wrapping to include SessionResetter.
• Regenerated optionalMethodsConn to ensure SessionResetter is properly implemented.
• This allows MySQL driver resetSession method to be called to determine whether the connection is still valid before reuse.

Additional Notes

• The interface-wrapping tool was updated to recognize SessionResetter.
• optionalMethodsConn was regenerated to reflect this change.
• Tests have been validated to ensure correctness.
• No breaking changes introduced.

[CLAassistant]

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