unexpected EOF and busy buffer in (go-sql-driver/mysql) packets.go - mysql

Question

I am getting the unexpected EOF and busy buffer error in go-sql-driver/mysql despite after setting the SetConnMaxLifetime, SetMaxIdleConns and SetMaxOpenConns as suggested here. Can anyone tell me the proper solution of this issue nothing seems to work for me?
db, err := sql.Open("mysql", "USERNAME:PASSWORD#tcp(IP:PORT)/DB?charset=utf8")
checkErr(err)
db.SetConnMaxLifetime(time.Second * 5)
db.SetMaxIdleConns(0)
db.SetMaxOpenConns(151)
rows, err := db.Query("Select col1, col2, col3 from tbl")
checkErr(err)
for rows.Next() {
var col1 string
var col2 int32
var col3 uint64
err = rows.Scan(&col1, &col2, &col3)
checkErr(err)
Process(col1, col2, col3)
}

Answer 1

I setup a local MySQL database and ran your code:
package main
import (
"database/sql"
"fmt"
"log"
"time"
_ "github.com/go-sql-driver/mysql"
)
func main() {
db, err := sql.Open("mysql", "root#tcp(localhost)/test?charset=utf8")
if err != nil {
log.Fatalln(err)
}
db.SetConnMaxLifetime(time.Second * 5)
db.SetMaxIdleConns(0)
db.SetMaxOpenConns(151)
rows, err := db.Query("SELECT col1, col2, col3 FROM tbl2")
if err != nil {
log.Fatalln(err)
}
for rows.Next() {
var col1 string
var col2 int32
var col3 uint64
err = rows.Scan(&col1, &col2, &col3)
if err != nil {
log.Fatalln(err)
}
fmt.Println(col1, col2, col3)
}
}
..and it worked just fine for me. My CREATE TABLE statement looks like this:
CREATE TABLE `tbl2` (
`col1` varchar(25) DEFAULT NULL,
`col2` int(11) DEFAULT NULL,
`col3` bigint(20) unsigned DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
What does your table structure look like?

Answer 2

I found two ways for work arround the packets.go:36: unexpected EOF error, first way was changing driver to ziutek/mymysql driver, works ok and more or less with the same performance.
Second way, with the default driver, is to set db.SetMaxIdleConns(100) and db.SetMaxOpenConns(100), my mysql has max_connections to 151,
so I thought that limit to 100 will be ok.
In addition, prepared statements has speeded up a lot, before they were slower than Db.Query, now are at least twice as fast. (Tested with 200k queries in 20 goroutines)
I think the problem could be in file buffer.go of driver go-sql-driver/mysql, in line: nn, err := b.nc.Read(b.buf[n:]), some kind of timeout.

Answer 3

None of these worked for me. I have used the Docker container then I tried to log in to it from the local machine with MySQL client.
mysql -h localhost -P 3306 --protocol=tcp
After this go programme worked fine.

Answer 4

According to go-sql-driver/mysql/issues/314, bad_buffer could also happen when attempting to run multiple statements within a transaction while still having an open *sql.Rows.
Ensuring that all *sql.Rows were closed before running subsequent statements resolves the issue.
Before
rows, queryErr = tx.Query(selectQuery, queryArgs...)
// process rows.Next()
// Attempt to perform additional query
rows2, query2Err = tx.Query(selectQuery2, query2Args ...)
// Get bad_buffer error (from logs:)
// [mysql] {timestamp} packets.go:447: busy buffer
// [mysql] {timestamp} connection.go:173: bad connection
After
rows, queryErr = tx.Query(selectQuery, queryArgs...)
defer func(result *sql.Rows) {
_ = result.Close()
}(rows)
// process rows.Next()
// Attempt to perform additional query
rows2, query2Err = tx.Query(selectQuery2, query2Args ...)
defer func(result *sql.Rows) {
_ = result.Close()
}(rows2)
// No error