server: Rework NewConn/defaultServer

cmd/go-mysqlserver/main.go

@@ -26,7 +26,8 @@ func main() {
 
 	// 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{})
+	srv := server.NewDefaultServer()
+	conn, err := srv.NewConn(c, "root", "", server.EmptyHandler{})
 	if err != nil {
 		log.Fatal(err)
 	}

driver/driver_options_test.go

@@ -275,6 +275,8 @@ func CreateMockServer(t *testing.T) *testServer {
 
 	handler := &mockHandler{}
 
+	s := server.NewDefaultServer()
+
 	go func() {
 		for {
 			conn, err := l.Accept()
@@ -283,7 +285,7 @@ func CreateMockServer(t *testing.T) *testServer {
 			}
 
 			go func() {
-				co, err := server.NewCustomizedConn(conn, defaultServer, inMemProvider, handler)
+				co, err := s.NewCustomizedConn(conn, inMemProvider, handler)
 				if err != nil {
 					return
 				}

server/conn.go

@@ -3,6 +3,7 @@ package server
 import (
 	"errors"
 	"net"
+	"sync"
 	"sync/atomic"
 
 	"github.com/go-mysql-org/go-mysql/mysql"
@@ -36,51 +37,47 @@ type Conn struct {
 	closed atomic.Bool
 }
 
-var baseConnID uint32 = 10000
+var (
+	baseConnID    uint32 = 10000
+	defaultServer        = sync.OnceValue(func() *Server {
+		return NewDefaultServer()
+	})
+)
 
 // NewConn: create connection with default server settings
+//
+// Deprecated: Use [Server.NewConn] instead.
 func NewConn(conn net.Conn, user string, password string, h Handler) (*Conn, error) {
-	p := NewInMemoryProvider()
-	p.AddUser(user, password)
-
-	var packetConn *packet.Conn
-	if defaultServer.tlsConfig != nil {
-		packetConn = packet.NewTLSConn(conn)
-	} else {
-		packetConn = packet.NewConn(conn)
-	}
+	return defaultServer().NewConn(conn, user, password, h)
+}
 
-	c := &Conn{
-		Conn:               packetConn,
-		serverConf:         defaultServer,
-		credentialProvider: p,
-		h:                  h,
-		connectionID:       atomic.AddUint32(&baseConnID, 1),
-		stmts:              make(map[uint32]*Stmt),
-		salt:               mysql.RandomBuf(20),
-	}
-	c.closed.Store(false)
+// NewCustomizedConn: create connection with customized server settings
+//
+// Deprecated: Use [Server.NewCustomizedConn] instead.
+func NewCustomizedConn(conn net.Conn, serverConf *Server, p CredentialProvider, h Handler) (*Conn, error) {
+	return serverConf.NewCustomizedConn(conn, p, h)
+}
 
-	if err := c.handshake(); err != nil {
-		c.Close()
-		return nil, err
-	}
+// NewConn: create connection with default server settings
+func (s *Server) NewConn(conn net.Conn, user string, password string, h Handler) (*Conn, error) {
+	p := NewInMemoryProvider()
+	p.AddUser(user, password)
 
-	return c, nil
+	return s.NewCustomizedConn(conn, p, h)
 }
 
 // NewCustomizedConn: create connection with customized server settings
-func NewCustomizedConn(conn net.Conn, serverConf *Server, p CredentialProvider, h Handler) (*Conn, error) {
+func (s *Server) NewCustomizedConn(conn net.Conn, p CredentialProvider, h Handler) (*Conn, error) {
 	var packetConn *packet.Conn
-	if serverConf.tlsConfig != nil {
+	if s.tlsConfig != nil {
 		packetConn = packet.NewTLSConn(conn)
 	} else {
 		packetConn = packet.NewConn(conn)
 	}
 
 	c := &Conn{
 		Conn:               packetConn,
-		serverConf:         serverConf,
+		serverConf:         s,
 		credentialProvider: p,
 		h:                  h,
 		connectionID:       atomic.AddUint32(&baseConnID, 1),

server/server_conf.go

@@ -8,8 +8,6 @@ import (
 	"github.com/go-mysql-org/go-mysql/mysql"
 )
 
-var defaultServer = NewDefaultServer()
-
 // Defines a basic MySQL server with configs.
 //
 // We do not aim at implementing the whole MySQL connection suite to have the best compatibilities for the clients.