snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

test/subconn_test.go

@@ -0,0 +1,126 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package test
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/balancer/base"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/internal/balancer/stub"
+	"google.golang.org/grpc/internal/stubserver"
+	"google.golang.org/grpc/internal/testutils"
+	testpb "google.golang.org/grpc/interop/grpc_testing"
+	"google.golang.org/grpc/resolver"
+)
+
+type tsccPicker struct {
+	sc balancer.SubConn
+}
+
+func (p *tsccPicker) Pick(balancer.PickInfo) (balancer.PickResult, error) {
+	return balancer.PickResult{SubConn: p.sc}, nil
+}
+
+// TestSubConnEmpty tests that removing all addresses from a SubConn and then
+// re-adding them does not cause a panic and properly reconnects.
+func (s) TestSubConnEmpty(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	// sc is the one SubConn used throughout the test.  Created on demand and
+	// re-used on every update.
+	var sc balancer.SubConn
+
+	// Simple custom balancer that sets the address list to empty if the
+	// resolver produces no addresses.  Pickfirst, by default, will remove the
+	// SubConn in this case instead.
+	bal := stub.BalancerFuncs{
+		UpdateClientConnState: func(d *stub.BalancerData, ccs balancer.ClientConnState) error {
+			if sc == nil {
+				var err error
+				sc, err = d.ClientConn.NewSubConn(ccs.ResolverState.Addresses, balancer.NewSubConnOptions{
+					StateListener: func(state balancer.SubConnState) {
+						switch state.ConnectivityState {
+						case connectivity.Ready:
+							d.ClientConn.UpdateState(balancer.State{
+								ConnectivityState: connectivity.Ready,
+								Picker:            &tsccPicker{sc: sc},
+							})
+						case connectivity.TransientFailure:
+							d.ClientConn.UpdateState(balancer.State{
+								ConnectivityState: connectivity.TransientFailure,
+								Picker:            base.NewErrPicker(fmt.Errorf("error connecting: %v", state.ConnectionError)),
+							})
+						}
+					},
+				})
+				if err != nil {
+					t.Errorf("error creating initial subconn: %v", err)
+				}
+			} else {
+				d.ClientConn.UpdateAddresses(sc, ccs.ResolverState.Addresses)
+			}
+			sc.Connect()
+
+			if len(ccs.ResolverState.Addresses) == 0 {
+				d.ClientConn.UpdateState(balancer.State{
+					ConnectivityState: connectivity.TransientFailure,
+					Picker:            base.NewErrPicker(errors.New("no addresses")),
+				})
+			} else {
+				d.ClientConn.UpdateState(balancer.State{
+					ConnectivityState: connectivity.Connecting,
+					Picker:            &tsccPicker{sc: sc},
+				})
+			}
+			return nil
+		},
+	}
+	stub.Register("tscc", bal)
+
+	// Start the stub server with our stub balancer.
+	ss := &stubserver.StubServer{
+		EmptyCallF: func(context.Context, *testpb.Empty) (*testpb.Empty, error) {
+			return &testpb.Empty{}, nil
+		},
+	}
+	if err := ss.Start(nil, grpc.WithDefaultServiceConfig(`{"loadBalancingConfig": [{"tscc":{}}]}`)); err != nil {
+		t.Fatalf("Error starting server: %v", err)
+	}
+	defer ss.Stop()
+	if _, err := ss.Client.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+		t.Fatalf("EmptyCall failed: %v", err)
+	}
+
+	t.Log("Removing addresses from resolver and SubConn")
+	ss.R.UpdateState(resolver.State{Addresses: []resolver.Address{}})
+	testutils.AwaitState(ctx, t, ss.CC, connectivity.TransientFailure)
+
+	t.Log("Re-adding addresses to resolver and SubConn")
+	ss.R.UpdateState(resolver.State{Addresses: []resolver.Address{{Addr: ss.Address}}})
+	if _, err := ss.Client.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+		t.Fatalf("EmptyCall failed: %v", err)
+	}
+}