Handle the compatibility issue in GetClusterInfo RPC

Signed-off-by: Bin Shi <binshi.bing@gmail.com>

client/client.go

@@ -429,16 +429,14 @@ func (c *client) loadKeyspaceMeta(keyspace string) error {
 }
 
 func (c *client) setup() error {
+	// Init the metrics.
+	initAndRegisterMetrics(c.option.metricsLabels)
+
 	// Init the client base.
 	if err := c.pdSvcDiscovery.Init(); err != nil {
 		return err
 	}
 
-	// Init the metrics.
-	if c.option.initMetrics {
-		initAndRegisterMetrics(c.option.metricsLabels)
-	}
-
 	// Register callbacks
 	c.pdSvcDiscovery.AddServingAddrSwitchedCallback(c.scheduleUpdateTokenConnection)
 

client/pd_service_discovery.go

@@ -62,7 +62,7 @@ type ServiceDiscovery interface {
 	// GetKeyspaceGroupID returns the ID of the keyspace group
 	GetKeyspaceGroupID() uint32
 	// DiscoverServiceURLs discovers the microservice with the specified type and returns the server urls.
-	DiscoverMicroservice(svcType serviceType) []string
+	DiscoverMicroservice(svcType serviceType) ([]string, error)
 	// GetServiceURLs returns the URLs of the servers providing the service
 	GetServiceURLs() []string
 	// GetServingEndpointClientConn returns the grpc client connection of the serving endpoint
@@ -299,7 +299,7 @@ func (c *pdServiceDiscovery) GetKeyspaceGroupID() uint32 {
 }
 
 // DiscoverServiceURLs discovers the microservice with the specified type and returns the server urls.
-func (c *pdServiceDiscovery) DiscoverMicroservice(svcType serviceType) (urls []string) {
+func (c *pdServiceDiscovery) DiscoverMicroservice(svcType serviceType) (urls []string, err error) {
 	switch svcType {
 	case apiService:
 		urls = c.GetServiceURLs()
@@ -310,17 +310,18 @@ func (c *pdServiceDiscovery) DiscoverMicroservice(svcType serviceType) (urls []s
 			if err != nil {
 				log.Error("[pd] failed to get cluster info",
 					zap.String("leader-addr", leaderAddr), errs.ZapError(err))
-				return nil
+				return nil, err
 			}
 			urls = clusterInfo.TsoUrls
 		} else {
-			log.Error("[pd] failed to get leader addr")
+			err = errors.New("failed to get leader addr")
+			return nil, err
 		}
 	default:
 		panic("invalid service type")
 	}
 
-	return urls
+	return urls, nil
 }
 
 // GetServiceURLs returns the URLs of the servers.

client/tso_service_discovery.go

@@ -21,7 +21,9 @@ import (
 	"sync"
 	"time"
 
+	"github.com/gogo/protobuf/proto"
 	"github.com/pingcap/errors"
+	"github.com/pingcap/failpoint"
 	"github.com/pingcap/kvproto/pkg/tsopb"
 	"github.com/pingcap/log"
 	"github.com/tikv/pd/client/errs"
@@ -96,31 +98,6 @@ type tsoServerDiscovery struct {
 	failureCount int
 }
 
-func (t *tsoServerDiscovery) getTSOServer(sd ServiceDiscovery) (string, error) {
-	t.Lock()
-	defer t.Unlock()
-
-	if len(t.addrs) == 0 || t.failureCount == len(t.addrs) {
-		addrs := sd.DiscoverMicroservice(tsoService)
-		if len(addrs) == 0 {
-			return "", errors.New("no tso server address found")
-		}
-
-		log.Info("update tso server addresses", zap.Strings("addrs", addrs))
-
-		t.addrs = addrs
-		t.selectIdx = 0
-		t.failureCount = 0
-	}
-
-	// Pick a TSO server in a round-robin way.
-	tsoServerAddr := t.addrs[t.selectIdx]
-	t.selectIdx++
-	t.selectIdx %= len(t.addrs)
-
-	return tsoServerAddr, nil
-}
-
 func (t *tsoServerDiscovery) countFailure() {
 	t.Lock()
 	defer t.Unlock()
@@ -301,7 +278,7 @@ func (c *tsoServiceDiscovery) GetKeyspaceGroupID() uint32 {
 }
 
 // DiscoverServiceURLs discovers the microservice with the specified type and returns the server urls.
-func (c *tsoServiceDiscovery) DiscoverMicroservice(svcType serviceType) []string {
+func (c *tsoServiceDiscovery) DiscoverMicroservice(svcType serviceType) ([]string, error) {
 	var urls []string
 
 	switch svcType {
@@ -312,7 +289,7 @@ func (c *tsoServiceDiscovery) DiscoverMicroservice(svcType serviceType) []string
 		panic("invalid service type")
 	}
 
-	return urls
+	return urls, nil
 }
 
 // GetServiceURLs returns the URLs of the tso primary/secondary addresses of this keyspace group.
@@ -430,7 +407,7 @@ func (c *tsoServiceDiscovery) afterPrimarySwitched(oldPrimary, newPrimary string
 func (c *tsoServiceDiscovery) updateMember() error {
 	// The keyspace membership or the primary serving address of the keyspace group, to which this
 	// keyspace belongs, might have been changed. We need to query tso servers to get the latest info.
-	tsoServerAddr, err := c.tsoServerDiscovery.getTSOServer(c.apiSvcDiscovery)
+	tsoServerAddr, err := c.getTSOServer(c.apiSvcDiscovery)
 	if err != nil {
 		log.Error("[tso] failed to get tso server", errs.ZapError(err))
 		return err
@@ -526,3 +503,83 @@ func (c *tsoServiceDiscovery) findGroupByKeyspaceID(
 
 	return resp.KeyspaceGroup, nil
 }
+
+func (c *tsoServiceDiscovery) getTSOServer(sd ServiceDiscovery) (string, error) {
+	c.Lock()
+	defer c.Unlock()
+
+	var (
+		addrs []string
+		err   error
+	)
+	t := c.tsoServerDiscovery
+	if len(t.addrs) == 0 || t.failureCount == len(t.addrs) {
+		addrs, err = sd.DiscoverMicroservice(tsoService)
+		if err != nil {
+			return "", err
+		}
+		failpoint.Inject("serverReturnsNoTSOAddrs", func() {
+			addrs = nil
+		})
+		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")
+			}
+		}
+
+		log.Info("update tso server addresses", zap.Strings("addrs", addrs))
+
+		t.addrs = addrs
+		t.selectIdx = 0
+		t.failureCount = 0
+	}
+
+	// Pick a TSO server in a round-robin way.
+	tsoServerAddr := t.addrs[t.selectIdx]
+	t.selectIdx++
+	t.selectIdx %= len(t.addrs)
+
+	return tsoServerAddr, nil
+}
+
+func (c *tsoServiceDiscovery) discoverWithLegacyPath() ([]string, error) {
+	resp, err := c.metacli.Get(c.ctx, []byte(c.defaultDiscoveryKey))
+	if err != nil {
+		log.Error("[tso] failed to get the kesypace serving endpoint",
+			zap.String("discovery-key", c.defaultDiscoveryKey), errs.ZapError(err))
+		return nil, err
+	}
+	if resp == nil || len(resp.Kvs) == 0 {
+		log.Error("[tso] didn't find the keyspace serving endpoint",
+			zap.String("primary-key", c.defaultDiscoveryKey))
+		return nil, errs.ErrClientGetServingEndpoint
+	} else if resp.Count > 1 {
+		return nil, errs.ErrClientGetMultiResponse.FastGenByArgs(resp.Kvs)
+	}
+
+	value := resp.Kvs[0].Value
+	primary := &tsopb.Participant{}
+	if err := proto.Unmarshal(value, primary); err != nil {
+		return nil, errs.ErrClientProtoUnmarshal.Wrap(err).GenWithStackByCause()
+	}
+	listenUrls := primary.GetListenUrls()
+	if len(listenUrls) == 0 {
+		log.Error("[tso] the keyspace serving endpoint list is empty",
+			zap.String("discovery-key", c.defaultDiscoveryKey))
+		return nil, errs.ErrClientGetServingEndpoint
+	}
+	return listenUrls, nil
+}

tests/integrations/tso/client_test.go

@@ -197,6 +197,34 @@ func (suite *tsoClientTestSuite) TestGetTSAsync() {
 	wg.Wait()
 }
 
+func (suite *tsoClientTestSuite) TestDiscoverTSOServiceWithLegacyPath() {
+	re := suite.Require()
+	var wg sync.WaitGroup
+	wg.Add(tsoRequestConcurrencyNumber)
+	for i := 0; i < tsoRequestConcurrencyNumber; i++ {
+		go func() {
+			defer wg.Done()
+			// 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)"))
+			defer func() {
+				re.NoError(failpoint.Disable("github.com/tikv/pd/client/serverReturnsNoTSOAddrs"))
+			}()
+			client := mcs.SetupClientWithDefaultKeyspaceName(
+				suite.ctx, re, strings.Split(suite.backendEndpoints, ","))
+			var lastTS uint64
+			for j := 0; j < tsoRequestRound; j++ {
+				physical, logical, err := client.GetTS(suite.ctx)
+				suite.NoError(err)
+				ts := tsoutil.ComposeTS(physical, logical)
+				suite.Less(lastTS, ts)
+				lastTS = ts
+			}
+		}()
+	}
+	wg.Wait()
+}
+
 // More details can be found in this issue: https://github.com/tikv/pd/issues/4884
 func (suite *tsoClientTestSuite) TestUpdateAfterResetTSO() {
 	re := suite.Require()