Send connection attributes (go-sql-driver#1389)

Co-authored-by: Inada Naoki <songofacandy@gmail.com>

.github/workflows/test.yml

@@ -84,6 +84,7 @@ jobs:
             ; TestConcurrent fails if max_connections is too large
             max_connections=50
             local_infile=1
+            performance_schema=on
       - name: setup database
         run: |
           mysql --user 'root' --host '127.0.0.1' -e 'create database gotest;'

README.md

@@ -393,6 +393,15 @@ Default:        0
 
 I/O write timeout. The value must be a decimal number with a unit suffix (*"ms"*, *"s"*, *"m"*, *"h"*), such as *"30s"*, *"0.5m"* or *"1m30s"*.
 
+##### `connectionAttributes`
+
+```
+Type:           comma-delimited string of user-defined "key:value" pairs
+Valid Values:   (<name1>:<value1>,<name2>:<value2>,...)
+Default:        none
+```
+
+[Connection attributes](https://dev.mysql.com/doc/refman/8.0/en/performance-schema-connection-attribute-tables.html) are key-value pairs that application programs can pass to the server at connect time.
 
 ##### System Variables
 

connection.go

@@ -27,6 +27,7 @@ type mysqlConn struct {
 	affectedRows     uint64
 	insertId         uint64
 	cfg              *Config
+	connector        *connector
 	maxAllowedPacket int
 	maxWriteSize     int
 	writeTimeout     time.Duration

connector.go

@@ -11,11 +11,54 @@ package mysql
 import (
 	"context"
 	"database/sql/driver"
+	"fmt"
 	"net"
+	"os"
+	"strconv"
+	"strings"
 )
 
 type connector struct {
-	cfg *Config // immutable private copy.
+	cfg               *Config // immutable private copy.
+	encodedAttributes string  // Encoded connection attributes.
+}
+
+func encodeConnectionAttributes(textAttributes string) string {
+	connAttrsBuf := make([]byte, 0, 251)
+
+	// default connection attributes
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrClientName)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrClientNameValue)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrOS)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrOSValue)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrPlatform)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrPlatformValue)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrPid)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, strconv.Itoa(os.Getpid()))
+
+	// user-defined connection attributes
+	for _, connAttr := range strings.Split(textAttributes, ",") {
+		attr := strings.SplitN(connAttr, ":", 2)
+		if len(attr) != 2 {
+			continue
+		}
+		for _, v := range attr {
+			connAttrsBuf = appendLengthEncodedString(connAttrsBuf, v)
+		}
+	}
+
+	return string(connAttrsBuf)
+}
+
+func newConnector(cfg *Config) (*connector, error) {
+	encodedAttributes := encodeConnectionAttributes(cfg.ConnectionAttributes)
+	if len(encodedAttributes) > 250 {
+		return nil, fmt.Errorf("connection attributes are longer than 250 bytes: %dbytes (%q)", len(encodedAttributes), cfg.ConnectionAttributes)
+	}
+	return &connector{
+		cfg:               cfg,
+		encodedAttributes: encodedAttributes,
+	}, nil
 }
 
 // Connect implements driver.Connector interface.
@@ -29,6 +72,7 @@ func (c *connector) Connect(ctx context.Context) (driver.Conn, error) {
 		maxWriteSize:     maxPacketSize - 1,
 		closech:          make(chan struct{}),
 		cfg:              c.cfg,
+		connector:        c,
 	}
 	mc.parseTime = mc.cfg.ParseTime
 

connector_test.go

@@ -8,13 +8,16 @@ import (
 )
 
 func TestConnectorReturnsTimeout(t *testing.T) {
-	connector := &connector{&Config{
+	connector, err := newConnector(&Config{
 		Net:     "tcp",
 		Addr:    "1.1.1.1:1234",
 		Timeout: 10 * time.Millisecond,
-	}}
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
 
-	_, err := connector.Connect(context.Background())
+	_, err = connector.Connect(context.Background())
 	if err == nil {
 		t.Fatal("error expected")
 	}

const.go

@@ -8,12 +8,24 @@
 
 package mysql
 
+import "runtime"
+
 const (
 	defaultAuthPlugin       = "mysql_native_password"
 	defaultMaxAllowedPacket = 64 << 20 // 64 MiB. See https://github.com/go-sql-driver/mysql/issues/1355
 	minProtocolVersion      = 10
 	maxPacketSize           = 1<<24 - 1
 	timeFormat              = "2006-01-02 15:04:05.999999"
+
+	// Connection attributes
+	// See https://dev.mysql.com/doc/refman/8.0/en/performance-schema-connection-attribute-tables.html#performance-schema-connection-attributes-available
+	connAttrClientName      = "_client_name"
+	connAttrClientNameValue = "Go-MySQL-Driver"
+	connAttrOS              = "_os"
+	connAttrOSValue         = runtime.GOOS
+	connAttrPlatform        = "_platform"
+	connAttrPlatformValue   = runtime.GOARCH
+	connAttrPid             = "_pid"
 )
 
 // MySQL constants documentation:

driver.go

@@ -74,8 +74,9 @@ func (d MySQLDriver) Open(dsn string) (driver.Conn, error) {
 	if err != nil {
 		return nil, err
 	}
-	c := &connector{
-		cfg: cfg,
+	c, err := newConnector(cfg)
+	if err != nil {
+		return nil, err
 	}
 	return c.Connect(context.Background())
 }
@@ -92,7 +93,7 @@ func NewConnector(cfg *Config) (driver.Connector, error) {
 	if err := cfg.normalize(); err != nil {
 		return nil, err
 	}
-	return &connector{cfg: cfg}, nil
+	return newConnector(cfg)
 }
 
 // OpenConnector implements driver.DriverContext.
@@ -101,7 +102,5 @@ func (d MySQLDriver) OpenConnector(dsn string) (driver.Connector, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &connector{
-		cfg: cfg,
-	}, nil
+	return newConnector(cfg)
 }

driver_test.go

@@ -3209,3 +3209,50 @@ func TestConnectorTimeoutsWatchCancel(t *testing.T) {
 		t.Errorf("connection not closed")
 	}
 }
+
+func TestConnectionAttributes(t *testing.T) {
+	if !available {
+		t.Skipf("MySQL server not running on %s", netAddr)
+	}
+
+	attr1 := "attr1"
+	value1 := "value1"
+	attr2 := "foo"
+	value2 := "boo"
+	dsn += fmt.Sprintf("&connectionAttributes=%s:%s,%s:%s", attr1, value1, attr2, value2)
+
+	var db *sql.DB
+	if _, err := ParseDSN(dsn); err != errInvalidDSNUnsafeCollation {
+		db, err = sql.Open("mysql", dsn)
+		if err != nil {
+			t.Fatalf("error connecting: %s", err.Error())
+		}
+		defer db.Close()
+	}
+
+	dbt := &DBTest{t, db}
+
+	var attrValue string
+	queryString := "SELECT ATTR_VALUE FROM performance_schema.session_account_connect_attrs WHERE PROCESSLIST_ID = CONNECTION_ID() and ATTR_NAME = ?"
+	rows := dbt.mustQuery(queryString, connAttrClientName)
+	if rows.Next() {
+		rows.Scan(&attrValue)
+		if attrValue != connAttrClientNameValue {
+			dbt.Errorf("expected %q, got %q", connAttrClientNameValue, attrValue)
+		}
+	} else {
+		dbt.Errorf("no data")
+	}
+	rows.Close()
+
+	rows = dbt.mustQuery(queryString, attr2)
+	if rows.Next() {
+		rows.Scan(&attrValue)
+		if attrValue != value2 {
+			dbt.Errorf("expected %q, got %q", value2, attrValue)
+		}
+	} else {
+		dbt.Errorf("no data")
+	}
+	rows.Close()
+}

dsn.go

@@ -34,22 +34,24 @@ var (
 // If a new Config is created instead of being parsed from a DSN string,
 // the NewConfig function should be used, which sets default values.
 type Config struct {
-	User             string            // Username
-	Passwd           string            // Password (requires User)
-	Net              string            // Network type
-	Addr             string            // Network address (requires Net)
-	DBName           string            // Database name
-	Params           map[string]string // Connection parameters
-	Collation        string            // Connection collation
-	Loc              *time.Location    // Location for time.Time values
-	MaxAllowedPacket int               // Max packet size allowed
-	ServerPubKey     string            // Server public key name
-	pubKey           *rsa.PublicKey    // Server public key
-	TLSConfig        string            // TLS configuration name
-	TLS              *tls.Config       // TLS configuration, its priority is higher than TLSConfig
-	Timeout          time.Duration     // Dial timeout
-	ReadTimeout      time.Duration     // I/O read timeout
-	WriteTimeout     time.Duration     // I/O write timeout
+	User                 string            // Username
+	Passwd               string            // Password (requires User)
+	Net                  string            // Network type
+	Addr                 string            // Network address (requires Net)
+	DBName               string            // Database name
+	Params               map[string]string // Connection parameters
+	ConnectionAttributes string            // Connection Attributes, comma-delimited string of user-defined "key:value" pairs
+	Collation            string            // Connection collation
+	Loc                  *time.Location    // Location for time.Time values
+	MaxAllowedPacket     int               // Max packet size allowed
+	ServerPubKey         string            // Server public key name
+	pubKey               *rsa.PublicKey    // Server public key
+	TLSConfig            string            // TLS configuration name
+	TLS                  *tls.Config       // TLS configuration, its priority is higher than TLSConfig
+	Timeout              time.Duration     // Dial timeout
+	ReadTimeout          time.Duration     // I/O read timeout
+	WriteTimeout         time.Duration     // I/O write timeout
+	Logger               Logger            // Logger
 
 	AllowAllFiles            bool // Allow all files to be used with LOAD DATA LOCAL INFILE
 	AllowCleartextPasswords  bool // Allows the cleartext client side plugin
@@ -554,6 +556,11 @@ func parseDSNParams(cfg *Config, params string) (err error) {
 			if err != nil {
 				return
 			}
+
+		// Connection attributes
+		case "connectionAttributes":
+			cfg.ConnectionAttributes = value
+
 		default:
 			// lazy init
 			if cfg.Params == nil {

packets.go

@@ -285,6 +285,7 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		clientLocalFiles |
 		clientPluginAuth |
 		clientMultiResults |
+		clientConnectAttrs |
 		mc.flags&clientLongFlag
 
 	if mc.cfg.ClientFoundRows {
@@ -318,6 +319,13 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		pktLen += n + 1
 	}
 
+	// 1 byte to store length of all key-values
+	// NOTE: Actually, this is length encoded integer.
+	// But we support only len(connAttrBuf) < 251 for now because takeSmallBuffer
+	// doesn't support buffer size more than 4096 bytes.
+	// TODO(methane): Rewrite buffer management.
+	pktLen += 1 + len(mc.connector.encodedAttributes)
+
 	// Calculate packet length and get buffer with that size
 	data, err := mc.buf.takeSmallBuffer(pktLen + 4)
 	if err != nil {
@@ -394,6 +402,11 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 	data[pos] = 0x00
 	pos++
 
+	// Connection Attributes
+	data[pos] = byte(len(mc.connector.encodedAttributes))
+	pos++
+	pos += copy(data[pos:], []byte(mc.connector.encodedAttributes))
+
 	// Send Auth packet
 	return mc.writePacket(data[:pos])
 }

packets_test.go

@@ -96,9 +96,14 @@ var _ net.Conn = new(mockConn)
 
 func newRWMockConn(sequence uint8) (*mockConn, *mysqlConn) {
 	conn := new(mockConn)
+	connector, err := newConnector(NewConfig())
+	if err != nil {
+		panic(err)
+	}
 	mc := &mysqlConn{
 		buf:              newBuffer(conn),
-		cfg:              NewConfig(),
+		cfg:              connector.cfg,
+		connector:        connector,
 		netConn:          conn,
 		closech:          make(chan struct{}),
 		maxAllowedPacket: defaultMaxAllowedPacket,

utils.go

@@ -616,6 +616,11 @@ func appendLengthEncodedInteger(b []byte, n uint64) []byte {
 		byte(n>>32), byte(n>>40), byte(n>>48), byte(n>>56))
 }
 
+func appendLengthEncodedString(b []byte, s string) []byte {
+	b = appendLengthEncodedInteger(b, uint64(len(s)))
+	return append(b, s...)
+}
+
 // reserveBuffer checks cap(buf) and expand buffer to len(buf) + appendSize.
 // If cap(buf) is not enough, reallocate new buffer.
 func reserveBuffer(buf []byte, appendSize int) []byte {