Description
Issue description
When using a persistent connection to a MySQL server, if the server is restarted, the old connection is left in a CLOSE_WAIT state on the client (suggesting the Go program has not detected the socket was closed).
E.g.
service mysql restart
netstat -tnp
tcp 35 0 127.0.0.1:51890 127.0.0.1:3306 CLOSE_WAIT 7662/db
This means that the next time the Go program tries to run a query, the dead connection is used and we get the error:
MySQL error: commands out of sync. You can't run this command now
The dead connection is then removed by the SQL drive and reconnects to the server.
Further queries run OK.
Example code
package main
import _ "github.com/go-sql-driver/mysql"
import "database/sql"
import "fmt"
import "time"
func main() {
db, err := sql.Open("mysql", "root:@tcp(127.0.0.1:3306)/mysql")
if err != nil {
fmt.Println("Open error: ", err)
return
}
err = db.Ping()
if err != nil {
fmt.Println("Ping error: ", err)
return
}
fmt.Println("Ping OK")
var connId int
for {
if err := db.QueryRow("SELECT CONNECTION_ID()").Scan(&connId); err != nil {
fmt.Println("MySQL error: ", err)
time.Sleep(10 * time.Second)
continue
}
fmt.Println("Conn ID: ", connId)
time.Sleep(10 * time.Second)
}
}Error log
[root@tpel6 ~]# go run db.go
Ping OK
Conn ID: 1519
Conn ID: 1519
Conn ID: 1519
Conn ID: 1519
Conn ID: 1519
Conn ID: 1519
Conn ID: 1519
Conn ID: 1519
MySQL error: commands out of sync. You can't run this command now
[mysql] 2016/04/21 11:55:38 packets.go:405: busy buffer
[mysql] 2016/04/21 11:55:38 packets.go:386: busy buffer
Conn ID: 11
Conn ID: 11
Conn ID: 11
Conn ID: 11
Configuration
Driver version (or git SHA):
"ImportPath": "github.com/go-sql-driver/mysql",
"Comment": "v1.2-194-g7ebe0a5",
"Rev": "7ebe0a500653eeb1859664bed5e48dec1e164e73"
Go version: run go version in your console
go version go1.6.2 linux/amd64
Server version: E.g. MySQL 5.6, MariaDB 10.0.20
Server version: 10.0.24-MariaDB MariaDB Server
Server OS: E.g. Debian 8.1 (Jessie), Windows 10
CentOS 6.7 x86_64