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go-mysql

A pure go library to handle MySQL network protocol and replication as used by MySQL and MariaDB.

Changelog

This repo uses Changelog.

Content

• Replication - Process events from a binlog stream.
• Incremental dumping - Sync from MySQL to Redis, Elasticsearch, etc.
• Client - Simple MySQL client.
• Fake server - server side of the MySQL protocol, as library.
• database/sql like driver - An alternative database/sql driver for MySQL.
• Logging - Custom logging options.
• Migration - Information for how to migrate if you used the old location of this project.

Examples

The cmd directory contains example applications that can be build by running make build in the root of the project. The resulting binaries will be places in bin/.

• go-binlogparser: parses a binlog file at a given offset
• go-canal: streams binlog events from a server to canal
• go-mysqlbinlog: streams binlog events
• go-mysqldump: like mysqldump, but in Go
• go-mysqlserver: fake MySQL server

Replication

Replication package handles MySQL replication protocol like python-mysql-replication.

You can use it as a MySQL replica to sync binlog from master then do something, like updating cache, etc...

Example

import (
	"github.com/go-mysql-org/go-mysql/replication"
	"os"
)
// Create a binlog syncer with a unique server id, the server id must be different from other MySQL's. 
// flavor is mysql or mariadb
cfg := replication.BinlogSyncerConfig {
	ServerID: 100,
	Flavor:   "mysql",
	Host:     "127.0.0.1",
	Port:     3306,
	User:     "root",
	Password: "",
}
syncer := replication.NewBinlogSyncer(cfg)

// Start sync with specified binlog file and position
streamer, _ := syncer.StartSync(mysql.Position{binlogFile, binlogPos})

// or you can start a gtid replication like
// gtidSet, _ := mysql.ParseGTIDSet(mysql.MySQLFlavor, "de278ad0-2106-11e4-9f8e-6edd0ca20947:1-2")
// streamer, _ := syncer.StartSyncGTID(gtidSet)
// the mysql GTID set is like this "de278ad0-2106-11e4-9f8e-6edd0ca20947:1-2" and uses mysql.MySQLFlavor
// the mariadb GTID set is like this "0-1-100" and uses mysql.MariaDBFlavor

for {
	ev, _ := streamer.GetEvent(context.Background())
	// Dump event
	ev.Dump(os.Stdout)
}

// or we can use a timeout context
for {
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	ev, err := streamer.GetEvent(ctx)
	cancel()

	if err == context.DeadlineExceeded {
		// meet timeout
		continue
	}

	ev.Dump(os.Stdout)
}

The output looks:

=== RotateEvent ===
Date: 1970-01-01 08:00:00
Log position: 0
Event size: 43
Position: 4
Next log name: mysql.000002

=== FormatDescriptionEvent ===
Date: 2014-12-18 16:36:09
Log position: 120
Event size: 116
Version: 4
Server version: 5.6.19-log
Create date: 2014-12-18 16:36:09

=== QueryEvent ===
Date: 2014-12-18 16:38:24
Log position: 259
Event size: 139
Salve proxy ID: 1
Execution time: 0
Error code: 0
Schema: test
Query: DROP TABLE IF EXISTS `test_replication` /* generated by server */

Canal

Canal is a package that can sync your MySQL into everywhere, like Redis, Elasticsearch.

First, canal will dump your MySQL data then sync changed data using binlog incrementally.

You must use ROW format for binlog, full binlog row image is preferred, because we may meet some errors when primary key changed in update for minimal or noblob row image.

A simple example:

package main

import (
	"github.com/go-mysql-org/go-mysql/canal"
	"github.com/siddontang/go-log/log"
)

type MyEventHandler struct {
	canal.DummyEventHandler
}

func (h *MyEventHandler) OnRow(e *canal.RowsEvent) error {
	log.Infof("%s %v\n", e.Action, e.Rows)
	return nil
}

func (h *MyEventHandler) String() string {
	return "MyEventHandler"
}

func main() {
	cfg := canal.NewDefaultConfig()
	cfg.Addr = "127.0.0.1:3306"
	cfg.User = "root"
	// We only care table canal_test in test db
	cfg.Dump.TableDB = "test"
	cfg.Dump.Tables = []string{"canal_test"}

	c, err := canal.NewCanal(cfg)
	if err != nil {
		log.Fatal(err)
	}

	// Register a handler to handle RowsEvent
	c.SetEventHandler(&MyEventHandler{})

	// Start canal
	c.Run()
}

You can see go-mysql-elasticsearch for how to sync MySQL data into Elasticsearch.

Client

Client package supports a simple MySQL connection driver which you can use it to communicate with MySQL server.

Example

import (
	"github.com/go-mysql-org/go-mysql/client"
)

// Connect MySQL at 127.0.0.1:3306, with user root, an empty password and database test
conn, _ := client.Connect("127.0.0.1:3306", "root", "", "test")

// Or to use SSL/TLS connection if MySQL server supports TLS
//conn, _ := client.Connect("127.0.0.1:3306", "root", "", "test", func(c *Conn) {c.UseSSL(true)})

// Or to set your own client-side certificates for identity verification for security
//tlsConfig := NewClientTLSConfig(caPem, certPem, keyPem, false, "your-server-name")
//conn, _ := client.Connect("127.0.0.1:3306", "root", "", "test", func(c *Conn) {c.SetTLSConfig(tlsConfig)})

conn.Ping()

// Insert
r, _ := conn.Execute(`insert into table (id, name) values (1, "abc")`)

// Get last insert id
println(r.InsertId)
// Or affected rows count
println(r.AffectedRows)

// Select
r, err := conn.Execute(`select id, name from table where id = 1`)

// Close result for reuse memory (it's not necessary but very useful)
defer r.Close()

// Handle resultset
v, _ := r.GetInt(0, 0)
v, _ = r.GetIntByName(0, "id")

// Direct access to fields
for _, row := range r.Values {
	for _, val := range row {
		_ = val.Value() // interface{}
		// or
		if val.Type == mysql.FieldValueTypeFloat {
			_ = val.AsFloat64() // float64
		}
	}   
}

Tested MySQL versions for the client include:

• 5.5.x
• 5.6.x
• 5.7.x
• 8.0.x

Example for SELECT streaming (v1.1.1)

You can use also streaming for large SELECT responses. The callback function will be called for every result row without storing the whole resultset in memory. result.Fields will be filled before the first callback call.

// ...
var result mysql.Result
err := conn.ExecuteSelectStreaming(`select id, name from table LIMIT 100500`, &result, func(row []mysql.FieldValue) error {
    for idx, val := range row {
    	field := result.Fields[idx]
    	// You must not save FieldValue.AsString() value after this callback is done.
    	// Copy it if you need.
    	// ...
    }
    return nil
}, nil)

// ...

Example for connection pool (v1.3.0)

import (
    "github.com/go-mysql-org/go-mysql/client"
)

pool := client.NewPool(log.Debugf, 100, 400, 5, "127.0.0.1:3306", `root`, ``, `test`)
// ...
conn, _ := pool.GetConn(ctx)
defer pool.PutConn(conn)

conn.Execute() / conn.Begin() / etc...

Server

Server package supplies a framework to implement a simple MySQL server which can handle the packets from the MySQL client. You can use it to build your own MySQL proxy. The server connection is compatible with MySQL 5.5, 5.6, 5.7, and 8.0 versions, so that most MySQL clients should be able to connect to the Server without modifications.

Example

Minimalistic MySQL server implementation:

package main

import (
	"log"
	"net"

	"github.com/go-mysql-org/go-mysql/server"
)

func main() {
	// Listen for connections on localhost port 4000
	l, err := net.Listen("tcp", "127.0.0.1:4000")
	if err != nil {
		log.Fatal(err)
	}

	// Accept a new connection once
	c, err := l.Accept()
	if err != nil {
		log.Fatal(err)
	}

	// Create a connection with user root and an empty password.
	// You can use your own handler to handle command here.
	conn, err := server.NewConn(c, "root", "", server.EmptyHandler{})
	if err != nil {
		log.Fatal(err)
	}

	// as long as the client keeps sending commands, keep handling them
	for {
		if err := conn.HandleCommand(); err != nil {
			log.Fatal(err)
		}
	}
}

Another shell

$ mysql -h127.0.0.1 -P4000 -uroot
Your MySQL connection id is 10001
Server version: 5.7.0

MySQL [(none)]>
// Since EmptyHandler implements no commands, it will throw an error on any query that you will send

NewConn() will use default server configurations:

1. automatically generate default server certificates and enable TLS/SSL support.
2. support three mainstream authentication methods 'mysql_native_password', 'caching_sha2_password', and 'sha256_password' and use 'mysql_native_password' as default.
3. use an in-memory user credential provider to store user and password.

To customize server configurations, use NewServer() and create connection via NewCustomizedConn().

Driver

Driver is the package that you can use go-mysql with go database/sql like other drivers. A simple example:

package main

import (
	"database/sql"

	_ "github.com/go-mysql-org/go-mysql/driver"
)

func main() {
	// dsn format: "user:password@addr?dbname"
	dsn := "root@127.0.0.1:3306?test"
	db, _ := sql.Open("mysql", dsn)
	db.Close()
}

Driver Options

Configuration options can be provided by the standard DSN (Data Source Name).

[user[:password]@]addr[/db[?param=X]]

collation

Set a collation during the Auth handshake.

compress

Enable compression between the client and the server. Valid values are 'zstd','zlib','uncompressed'.

readTimeout

I/O read timeout. The time unit is specified in the argument value using golang's ParseDuration format.

0 means no timeout.

ssl

Enable TLS between client and server. Valid values are true or custom. When using custom, the connection will use the TLS configuration set by SetCustomTLSConfig matching the host.

timeout

Timeout is the maximum amount of time a dial will wait for a connect to complete. The time unit is specified in the argument value using golang's ParseDuration format.

0 means no timeout.

writeTimeout

I/O write timeout. The time unit is specified in the argument value using golang's ParseDuration format.

0 means no timeout.

retries

Allows disabling the golang database/sql default behavior to retry errors when ErrBadConn is returned by the driver. When retries are disabled this driver will not return ErrBadConn from the database/sql package.

Valid values are on (default) and off.

Custom Driver Options

The driver package exposes the function SetDSNOptions, allowing for modification of the connection by adding custom driver options. It requires a full import of the driver (not by side-effects only).

Example of defining a custom option:

import (
 "database/sql"

 "github.com/go-mysql-org/go-mysql/driver"
)

func main() {
 driver.SetDSNOptions(map[string]DriverOption{
  "no_metadata": func(c *client.Conn, value string) error {
   c.SetCapability(mysql.CLIENT_OPTIONAL_RESULTSET_METADATA)
   return nil
  },
 })

 // dsn format: "user:password@addr/dbname?"
 dsn := "root@127.0.0.1:3306/test?no_metadata=true"
 db, _ := sql.Open(dsn)
 db.Close()
}

Custom Driver Name

A custom driver name can be set via build options: -ldflags '-X "github.com/go-mysql-org/go-mysql/driver.driverName=gomysql"'.

This can be useful when using GORM:

import (
  _ "github.com/go-mysql-org/go-mysql/driver"
  "gorm.io/driver/mysql"
  "gorm.io/gorm"
)

db, err := gorm.Open(mysql.New(mysql.Config{
  DriverName: "gomysql",
  DSN: "gorm:gorm@127.0.0.1:3306/test",
}))

Custom NamedValueChecker

Golang allows for custom handling of query arguments before they are passed to the driver with the implementation of a NamedValueChecker. By doing a full import of the driver (not by side-effects only), a custom NamedValueChecker can be implemented.

import (
 "database/sql"

 "github.com/go-mysql-org/go-mysql/driver"
)

func main() {
 driver.AddNamedValueChecker(func(nv *sqlDriver.NamedValue) error {
  rv := reflect.ValueOf(nv.Value)
  if rv.Kind() != reflect.Uint64 {
   // fallback to the default value converter when the value is not a uint64
   return sqlDriver.ErrSkip
  }

  return nil
 })

 conn, err := sql.Open("mysql", "root@127.0.0.1:3306/test")
 defer conn.Close()

 stmt, err := conn.Prepare("select * from table where id = ?")
 defer stmt.Close()
 var val uint64 = math.MaxUint64
 // without the NamedValueChecker this query would fail
 result, err := stmt.Query(val)
}

We pass all tests in https://github.com/bradfitz/go-sql-test using go-mysql driver. :-)

Logging

Logging by default is send to stdout.

To disable logging completely:

import "github.com/siddontang/go-log/log"
...
        nullHandler, _ := log.NewNullHandler()
        cfg.Logger = log.NewDefault(nullHandler)

To write logging to any io.Writer:

import "github.com/siddontang/go-log/log"
...
        w := ...
        streamHandler, _ := log.NewStreamHandler(w)
        cfg.Logger = log.NewDefault(streamHandler)

Or you can implement your own log.Handler.

How to migrate to this repo

To change the used package in your repo it's enough to add this replace directive to your go.mod:

replace github.com/siddontang/go-mysql => github.com/go-mysql-org/go-mysql v1.10.0

This can be done by running this command:

go mod edit -replace=github.com/siddontang/go-mysql=github.com/go-mysql-org/go-mysql@v1.10.0

v1.10.0 - is the last tag in repo, feel free to choose what you want.

Credits

go-mysql was started by @siddontang and has many contributors