endpoints: implement Update method for EndpointManager.

- Add integration test for endpoints and resolver.

pkg/grpc_testing/stub_server.go

@@ -0,0 +1,86 @@
+package grpc_testing
+
+import (
+	"context"
+	"fmt"
+	"net"
+
+	"google.golang.org/grpc"
+	testpb "google.golang.org/grpc/test/grpc_testing"
+)
+
+// StubServer is borrowed from the interal package of grpc-go.
+// See https://github.com/grpc/grpc-go/blob/master/internal/stubserver/stubserver.go
+// Since it cannot be imported directly, we have to copy and paste it here,
+// and useless code for our testing is removed.
+
+// StubServer is a server that is easy to customize within individual test
+// cases.
+type StubServer struct {
+	// Guarantees we satisfy this interface; panics if unimplemented methods are called.
+	testpb.TestServiceServer
+
+	EmptyCallF      func(ctx context.Context, in *testpb.Empty) (*testpb.Empty, error)
+	UnaryCallF      func(ctx context.Context, in *testpb.SimpleRequest) (*testpb.SimpleResponse, error)
+	FullDuplexCallF func(stream testpb.TestService_FullDuplexCallServer) error
+
+	s *grpc.Server
+
+	// Network and Address are parameters for Listen. Defaults will be used if these are empty before Start.
+	Network string
+	Address string
+
+	cleanups []func() // Lambdas executed in Stop(); populated by Start().
+}
+
+// EmptyCall is the handler for testpb.EmptyCall.
+func (ss *StubServer) EmptyCall(ctx context.Context, in *testpb.Empty) (*testpb.Empty, error) {
+	return ss.EmptyCallF(ctx, in)
+}
+
+// UnaryCall is the handler for testpb.UnaryCall.
+func (ss *StubServer) UnaryCall(ctx context.Context, in *testpb.SimpleRequest) (*testpb.SimpleResponse, error) {
+	return ss.UnaryCallF(ctx, in)
+}
+
+// FullDuplexCall is the handler for testpb.FullDuplexCall.
+func (ss *StubServer) FullDuplexCall(stream testpb.TestService_FullDuplexCallServer) error {
+	return ss.FullDuplexCallF(stream)
+}
+
+// Start starts the server and creates a client connected to it.
+func (ss *StubServer) Start(sopts []grpc.ServerOption, dopts ...grpc.DialOption) error {
+	if ss.Network == "" {
+		ss.Network = "tcp"
+	}
+	if ss.Address == "" {
+		ss.Address = "localhost:0"
+	}
+
+	lis, err := net.Listen(ss.Network, ss.Address)
+	if err != nil {
+		return fmt.Errorf("net.Listen(%q, %q) = %v", ss.Network, ss.Address, err)
+	}
+	ss.Address = lis.Addr().String()
+	ss.cleanups = append(ss.cleanups, func() { lis.Close() })
+
+	s := grpc.NewServer(sopts...)
+	testpb.RegisterTestServiceServer(s, ss)
+	go s.Serve(lis)
+	ss.cleanups = append(ss.cleanups, s.Stop)
+	ss.s = s
+
+	return nil
+}
+
+// Stop stops ss and cleans up all resources it consumed.
+func (ss *StubServer) Stop() {
+	for i := len(ss.cleanups) - 1; i >= 0; i-- {
+		ss.cleanups[i]()
+	}
+}
+
+// Addr gets the address the server listening on.
+func (ss *StubServer) Addr() string {
+	return ss.Address
+}