TSO microservice discovery fallback path shouldn't call FindGroupByKeyspaceID

client/tso_service_discovery.go

@@ -413,14 +413,43 @@ func (c *tsoServiceDiscovery) updateMember() error {
 		log.Error("[tso] failed to get tso server", errs.ZapError(err))
 		return err
 	}
-	keyspaceGroup, err := c.findGroupByKeyspaceID(c.keyspaceID, tsoServerAddr, updateMemberTimeout)
-	if err != nil {
-		if c.tsoServerDiscovery.countFailure() {
-			log.Error("[tso] failed to find the keyspace group", errs.ZapError(err))
+
+	var keyspaceGroup *tsopb.KeyspaceGroup
+	if len(tsoServerAddr) > 0 {
+		keyspaceGroup, err = c.findGroupByKeyspaceID(c.keyspaceID, tsoServerAddr, updateMemberTimeout)
+		if err != nil {
+			if c.tsoServerDiscovery.countFailure() {
+				log.Error("[tso] failed to find the keyspace group", errs.ZapError(err))
+			}
+			return err
+		}
+		c.tsoServerDiscovery.resetFailure()
+	} else {
+		// There is no error but no tso server address found, which means
+		// the server side hasn't been upgraded to the version that
+		// processes and returns GetClusterInfoResponse.TsoUrls. In this case,
+		// we fall back to the old way of discovering the tso primary addresses
+		// from etcd directly.
+		log.Warn("[tso] no tso server address found,"+
+			" fallback to the legacy path to discover from etcd directly",
+			zap.String("discovery-key", c.defaultDiscoveryKey))
+		addrs, err := c.discoverWithLegacyPath()
+		if err != nil {
+			return err
+		}
+		if len(addrs) == 0 {
+			return errors.New("no tso server address found")
+		}
+		members := make([]*tsopb.KeyspaceGroupMember, 0, len(addrs))
+		for _, addr := range addrs {
+			members = append(members, &tsopb.KeyspaceGroupMember{Address: addr})
+		}
+		members[0].IsPrimary = true
+		keyspaceGroup = &tsopb.KeyspaceGroup{
+			Id:      c.keyspaceID,
+			Members: members,
 		}
-		return err
 	}
-	c.tsoServerDiscovery.resetFailure()
 
 	log.Info("[tso] update keyspace group", zap.String("keyspace-group", keyspaceGroup.String()))
 
@@ -470,6 +499,9 @@ func (c *tsoServiceDiscovery) updateMember() error {
 func (c *tsoServiceDiscovery) findGroupByKeyspaceID(
 	keyspaceID uint32, tsoSrvAddr string, timeout time.Duration,
 ) (*tsopb.KeyspaceGroup, error) {
+	failpoint.Inject("unexpectedCallOfFindGroupByKeyspaceID", func() {
+		panic("findGroupByKeyspaceID is called unexpectedly")
+	})
 	ctx, cancel := context.WithTimeout(c.ctx, timeout)
 	defer cancel()
 
@@ -526,21 +558,10 @@ func (c *tsoServiceDiscovery) getTSOServer(sd ServiceDiscovery) (string, error)
 		})
 		if len(addrs) == 0 {
 			// There is no error but no tso server address found, which means
-			// either the server side is experiencing some problems to get the
-			// tso primary addresses or the server hasn't been upgraded to the
-			// version which processes and returns GetClusterInfoResponse.TsoUrls.
-			// In this case, we fall back to the old way of discovering the tso
-			// primary addresses from etcd directly.
-			log.Warn("[tso] no tso server address found,"+
-				" fallback to the legacy path to discover from etcd directly",
-				zap.String("discovery-key", c.defaultDiscoveryKey))
-			addrs, err = c.discoverWithLegacyPath()
-			if err != nil {
-				return "", err
-			}
-			if len(addrs) == 0 {
-				return "", errors.New("no tso server address found")
-			}
+			// the server side hasn't been upgraded to the version that
+			// processes and returns GetClusterInfoResponse.TsoUrls. Return here
+			// and handle the fallback logic outside of this function.
+			return "", nil
 		}
 
 		log.Info("update tso server addresses", zap.Strings("addrs", addrs))

tests/integrations/tso/client_test.go

@@ -230,9 +230,12 @@ func (suite *tsoClientTestSuite) TestDiscoverTSOServiceWithLegacyPath() {
 	// Simulate the case that the server has lower version than the client and returns no tso addrs
 	// in the GetClusterInfo RPC.
 	re.NoError(failpoint.Enable("github.com/tikv/pd/client/serverReturnsNoTSOAddrs", `return(true)`))
+	re.NoError(failpoint.Enable("github.com/tikv/pd/client/unexpectedCallOfFindGroupByKeyspaceID", `return(true)`))
 	defer func() {
 		re.NoError(failpoint.Disable("github.com/tikv/pd/client/serverReturnsNoTSOAddrs"))
+		re.NoError(failpoint.Disable("github.com/tikv/pd/client/unexpectedCallOfFindGroupByKeyspaceID"))
 	}()
+
 	var wg sync.WaitGroup
 	wg.Add(tsoRequestConcurrencyNumber)
 	for i := 0; i < tsoRequestConcurrencyNumber; i++ {