fix: fix crash when enable standby and streaming (#38239)

issue: #38125

- connect kv at standby mode.
- make balancer initialization lazy.

Signed-off-by: chyezh <chyezh@outlook.com>

internal/datacoord/server.go

@@ -110,6 +110,7 @@ type Server struct {
 	address        string
 	watchClient    kv.WatchKV
 	kv             kv.MetaKv
+	metaRootPath   string
 	meta           *meta
 	segmentManager Manager
 	allocator      allocator.Allocator
@@ -306,6 +307,15 @@ func (s *Server) Init() error {
 	if err = s.initSession(); err != nil {
 		return err
 	}
+	if err := s.initKV(); err != nil {
+		return err
+	}
+	if streamingutil.IsStreamingServiceEnabled() {
+		s.streamingCoord = streamingcoord.NewServerBuilder().
+			WithETCD(s.etcdCli).
+			WithMetaKV(s.kv).
+			WithSession(s.session).Build()
+	}
 	if s.enableActiveStandBy {
 		s.activateFunc = func() error {
 			log.Info("DataCoord switch from standby to active, activating")
@@ -365,10 +375,7 @@ func (s *Server) initDataCoord() error {
 
 	// Initialize streaming coordinator.
 	if streamingutil.IsStreamingServiceEnabled() {
-		s.streamingCoord = streamingcoord.NewServerBuilder().
-			WithETCD(s.etcdCli).
-			WithMetaKV(s.kv).
-			WithSession(s.session).Build()
+
 		if err = s.streamingCoord.Init(context.TODO()); err != nil {
 			return err
 		}
@@ -648,31 +655,36 @@ func (s *Server) initSegmentManager() error {
 	return nil
 }
 
-func (s *Server) initMeta(chunkManager storage.ChunkManager) error {
-	if s.meta != nil {
+func (s *Server) initKV() error {
+	if s.kv != nil {
 		return nil
 	}
 	s.watchClient = etcdkv.NewEtcdKV(s.etcdCli, Params.EtcdCfg.MetaRootPath.GetValue(),
 		etcdkv.WithRequestTimeout(paramtable.Get().ServiceParam.EtcdCfg.RequestTimeout.GetAsDuration(time.Millisecond)))
 	metaType := Params.MetaStoreCfg.MetaStoreType.GetValue()
 	log.Info("data coordinator connecting to metadata store", zap.String("metaType", metaType))
-	metaRootPath := ""
 	if metaType == util.MetaStoreTypeTiKV {
-		metaRootPath = Params.TiKVCfg.MetaRootPath.GetValue()
-		s.kv = tikv.NewTiKV(s.tikvCli, metaRootPath,
+		s.metaRootPath = Params.TiKVCfg.MetaRootPath.GetValue()
+		s.kv = tikv.NewTiKV(s.tikvCli, s.metaRootPath,
 			tikv.WithRequestTimeout(paramtable.Get().ServiceParam.TiKVCfg.RequestTimeout.GetAsDuration(time.Millisecond)))
 	} else if metaType == util.MetaStoreTypeEtcd {
-		metaRootPath = Params.EtcdCfg.MetaRootPath.GetValue()
-		s.kv = etcdkv.NewEtcdKV(s.etcdCli, metaRootPath,
+		s.metaRootPath = Params.EtcdCfg.MetaRootPath.GetValue()
+		s.kv = etcdkv.NewEtcdKV(s.etcdCli, s.metaRootPath,
 			etcdkv.WithRequestTimeout(paramtable.Get().ServiceParam.EtcdCfg.RequestTimeout.GetAsDuration(time.Millisecond)))
 	} else {
 		return retry.Unrecoverable(fmt.Errorf("not supported meta store: %s", metaType))
 	}
 	log.Info("data coordinator successfully connected to metadata store", zap.String("metaType", metaType))
+	return nil
+}
 
+func (s *Server) initMeta(chunkManager storage.ChunkManager) error {
+	if s.meta != nil {
+		return nil
+	}
 	reloadEtcdFn := func() error {
 		var err error
-		catalog := datacoord.NewCatalog(s.kv, chunkManager.RootPath(), metaRootPath)
+		catalog := datacoord.NewCatalog(s.kv, chunkManager.RootPath(), s.metaRootPath)
 		s.meta, err = newMeta(s.ctx, catalog, chunkManager)
 		if err != nil {
 			return err

internal/streamingcoord/server/builder.go

@@ -4,10 +4,13 @@ import (
 	clientv3 "go.etcd.io/etcd/client/v3"
 
 	"github.com/milvus-io/milvus/internal/metastore/kv/streamingcoord"
+	"github.com/milvus-io/milvus/internal/streamingcoord/server/balancer"
 	"github.com/milvus-io/milvus/internal/streamingcoord/server/resource"
+	"github.com/milvus-io/milvus/internal/streamingcoord/server/service"
 	"github.com/milvus-io/milvus/internal/util/componentutil"
 	"github.com/milvus-io/milvus/internal/util/sessionutil"
 	"github.com/milvus-io/milvus/pkg/kv"
+	"github.com/milvus-io/milvus/pkg/util/syncutil"
 	"github.com/milvus-io/milvus/pkg/util/typeutil"
 )
 
@@ -41,8 +44,11 @@ func (s *ServerBuilder) Build() *Server {
 		resource.OptETCD(s.etcdClient),
 		resource.OptStreamingCatalog(streamingcoord.NewCataLog(s.metaKV)),
 	)
+	balancer := syncutil.NewFuture[balancer.Balancer]()
 	return &Server{
 		session:               s.session,
 		componentStateService: componentutil.NewComponentStateService(typeutil.StreamingCoordRole),
+		assignmentService:     service.NewAssignmentService(balancer),
+		balancer:              balancer,
 	}
 }

internal/streamingcoord/server/server.go

@@ -14,6 +14,7 @@ import (
 	"github.com/milvus-io/milvus/internal/util/streamingutil/util"
 	"github.com/milvus-io/milvus/pkg/log"
 	"github.com/milvus-io/milvus/pkg/streaming/proto/streamingpb"
+	"github.com/milvus-io/milvus/pkg/util/syncutil"
 )
 
 // Server is the streamingcoord server.
@@ -26,7 +27,7 @@ type Server struct {
 	componentStateService *componentutil.ComponentStateService // state.
 
 	// basic component variables can be used at service level.
-	balancer balancer.Balancer
+	balancer *syncutil.Future[balancer.Balancer]
 }
 
 // Init initializes the streamingcoord server.
@@ -39,7 +40,6 @@ func (s *Server) Init(ctx context.Context) (err error) {
 		return err
 	}
 	// Init all grpc service of streamingcoord server.
-	s.initService()
 	s.componentStateService.OnInitialized(s.session.GetServerID())
 	log.Info("streamingcoord server initialized")
 	return nil
@@ -51,15 +51,14 @@ func (s *Server) initBasicComponent(ctx context.Context) error {
 	var err error
 	// Read new incoming topics from configuration, and register it into balancer.
 	newIncomingTopics := util.GetAllTopicsFromConfiguration()
-	s.balancer, err = balancer.RecoverBalancer(ctx, "pchannel_count_fair", newIncomingTopics.Collect()...)
+	balancer, err := balancer.RecoverBalancer(ctx, "pchannel_count_fair", newIncomingTopics.Collect()...)
+	if err != nil {
+		return err
+	}
+	s.balancer.Set(balancer)
 	return err
 }
 
-// initService initializes the grpc service.
-func (s *Server) initService() {
-	s.assignmentService = service.NewAssignmentService(s.balancer)
-}
-
 // registerGRPCService register all grpc service to grpc server.
 func (s *Server) RegisterGRPCService(grpcServer *grpc.Server) {
 	streamingpb.RegisterStreamingCoordAssignmentServiceServer(grpcServer, s.assignmentService)
@@ -76,6 +75,6 @@ func (s *Server) Start() {
 func (s *Server) Stop() {
 	s.componentStateService.OnStopping()
 	log.Info("close balancer...")
-	s.balancer.Close()
+	s.balancer.Get().Close()
 	log.Info("streamingcoord server stopped")
 }

internal/streamingcoord/server/service/assignment.go

@@ -8,13 +8,14 @@ import (
 	"github.com/milvus-io/milvus/pkg/metrics"
 	"github.com/milvus-io/milvus/pkg/streaming/proto/streamingpb"
 	"github.com/milvus-io/milvus/pkg/util/paramtable"
+	"github.com/milvus-io/milvus/pkg/util/syncutil"
 )
 
 var _ streamingpb.StreamingCoordAssignmentServiceServer = (*assignmentServiceImpl)(nil)
 
 // NewAssignmentService returns a new assignment service.
 func NewAssignmentService(
-	balancer balancer.Balancer,
+	balancer *syncutil.Future[balancer.Balancer],
 ) streamingpb.StreamingCoordAssignmentServiceServer {
 	return &assignmentServiceImpl{
 		balancer:      balancer,
@@ -28,7 +29,7 @@ type AssignmentService interface {
 
 // assignmentServiceImpl is the implementation of the assignment service.
 type assignmentServiceImpl struct {
-	balancer      balancer.Balancer
+	balancer      *syncutil.Future[balancer.Balancer]
 	listenerTotal prometheus.Gauge
 }
 
@@ -37,5 +38,9 @@ func (s *assignmentServiceImpl) AssignmentDiscover(server streamingpb.StreamingC
 	s.listenerTotal.Inc()
 	defer s.listenerTotal.Dec()
 
-	return discover.NewAssignmentDiscoverServer(s.balancer, server).Execute()
+	balancer, err := s.balancer.GetWithContext(server.Context())
+	if err != nil {
+		return err
+	}
+	return discover.NewAssignmentDiscoverServer(balancer, server).Execute()
 }