auth: reconnect backend (#389)

Signed-off-by: disksing <i@disksing.com>

pkg/proxy/backend/authenticator.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/go-mysql-org/go-mysql/mysql"
+	gomysql "github.com/go-mysql-org/go-mysql/mysql"
 	"github.com/pingcap/tidb/util/hack"
 	"github.com/pingcap/tiproxy/lib/util/errors"
 	pnet "github.com/pingcap/tiproxy/pkg/proxy/net"
@@ -159,6 +160,8 @@ func (auth *Authenticator) handshakeFirstTime(logger *zap.Logger, cctx ConnConte
 	auth.attrs = clientResp.Attrs
 	auth.zstdLevel = clientResp.ZstdLevel
 
+RECONNECT:
+
 	// In case of testing, backendIO is passed manually that we don't want to bother with the routing logic.
 	backendIO, err := getBackendIO(cctx, auth, clientResp, 15*time.Second)
 	if err != nil {
@@ -214,7 +217,7 @@ func (auth *Authenticator) handshakeFirstTime(logger *zap.Logger, cctx ConnConte
 	pktIdx := 0
 loop:
 	for {
-		serverPkt, err := forwardMsg(backendIO, clientIO)
+		serverPkt, err := backendIO.ReadPacket()
 		if err != nil {
 			// tiproxy pp enabled, tidb pp disabled, tls disabled => invalid sequence
 			// tiproxy pp disabled, tidb pp enabled, tls disabled => invalid sequence
@@ -223,6 +226,23 @@ loop:
 			}
 			return err
 		}
+		var packetErr error
+		if serverPkt[0] == pnet.ErrHeader.Byte() {
+			packetErr = pnet.ParseErrorPacket(serverPkt)
+			if handshakeHandler.HandleHandshakeErr(cctx, packetErr.(*gomysql.MyError)) {
+				logger.Warn("handle handshake error, start reconnect", zap.Error(err))
+				backendIO.Close()
+				goto RECONNECT
+			}
+		}
+		err = clientIO.WritePacket(serverPkt, true)
+		if err != nil {
+			return err
+		}
+		if packetErr != nil {
+			return packetErr
+		}
+
 		pktIdx++
 		switch serverPkt[0] {
 		case pnet.OKHeader.Byte():
@@ -233,8 +253,6 @@ loop:
 				return err
 			}
 			return nil
-		case pnet.ErrHeader.Byte():
-			return pnet.ParseErrorPacket(serverPkt)
 		default: // mysql.AuthSwitchRequest, ShaCommand
 			if serverPkt[0] == pnet.AuthSwitchHeader.Byte() {
 				pluginName = string(serverPkt[1 : bytes.IndexByte(serverPkt[1:], 0)+1])

pkg/proxy/backend/handshake_handler.go

@@ -4,6 +4,7 @@
 package backend
 
 import (
+	gomysql "github.com/go-mysql-org/go-mysql/mysql"
 	"github.com/pingcap/tiproxy/lib/util/errors"
 	"github.com/pingcap/tiproxy/pkg/manager/namespace"
 	"github.com/pingcap/tiproxy/pkg/manager/router"
@@ -70,6 +71,7 @@ type ConnContext interface {
 
 type HandshakeHandler interface {
 	HandleHandshakeResp(ctx ConnContext, resp *pnet.HandshakeResp) error
+	HandleHandshakeErr(ctx ConnContext, err *gomysql.MyError) bool // return true means retry connect
 	GetRouter(ctx ConnContext, resp *pnet.HandshakeResp) (router.Router, error)
 	OnHandshake(ctx ConnContext, to string, err error)
 	OnConnClose(ctx ConnContext) error
@@ -94,6 +96,10 @@ func (handler *DefaultHandshakeHandler) HandleHandshakeResp(ConnContext, *pnet.H
 	return nil
 }
 
+func (handler *DefaultHandshakeHandler) HandleHandshakeErr(ctx ConnContext, err *gomysql.MyError) bool {
+	return false
+}
+
 func (handler *DefaultHandshakeHandler) GetRouter(ctx ConnContext, resp *pnet.HandshakeResp) (router.Router, error) {
 	ns, ok := handler.nsManager.GetNamespaceByUser(resp.User)
 	if !ok {
@@ -142,6 +148,7 @@ type CustomHandshakeHandler struct {
 	onTraffic           func(ConnContext)
 	onConnClose         func(ConnContext) error
 	handleHandshakeResp func(ctx ConnContext, resp *pnet.HandshakeResp) error
+	handleHandshakeErr  func(ctx ConnContext, err *gomysql.MyError) bool
 	getCapability       func() pnet.Capability
 	getServerVersion    func() string
 }
@@ -179,6 +186,13 @@ func (h *CustomHandshakeHandler) HandleHandshakeResp(ctx ConnContext, resp *pnet
 	return nil
 }
 
+func (h *CustomHandshakeHandler) HandleHandshakeErr(ctx ConnContext, err *gomysql.MyError) bool {
+	if h.handleHandshakeErr != nil {
+		return h.handleHandshakeErr(ctx, err)
+	}
+	return false
+}
+
 func (h *CustomHandshakeHandler) GetCapability() pnet.Capability {
 	if h.getCapability != nil {
 		return h.getCapability()