Handle server addresses update as client

agent/grpc-external/services/peerstream/replication.go

@@ -11,6 +11,7 @@ import (
 	"google.golang.org/protobuf/types/known/anypb"
 
 	"github.com/hashicorp/consul/agent/cache"
+	"github.com/hashicorp/consul/agent/consul/state"
 	"github.com/hashicorp/consul/agent/structs"
 	"github.com/hashicorp/consul/proto/pbpeering"
 	"github.com/hashicorp/consul/proto/pbpeerstream"
@@ -256,6 +257,7 @@ func (s *Server) handleUpsert(
 }
 
 // handleUpdateService handles both deletion and upsert events for a service.
+//
 //	On an UPSERT event:
 //		- All nodes, services, checks in the input pbNodes are re-applied through Raft.
 //		- Any nodes, services, or checks in the catalog that were not in the input pbNodes get deleted.
@@ -470,6 +472,33 @@ func (s *Server) handleUpsertRoots(
 	return s.Backend.PeeringTrustBundleWrite(req)
 }
 
+func (s *Server) handleUpsertServerAddrs(
+	peerName string,
+	partition string,
+	addrs *pbpeering.PeeringServerAddresses,
+) error {
+	q := state.Query{
+		Value:          peerName,
+		EnterpriseMeta: *structs.DefaultEnterpriseMetaInPartition(partition),
+	}
+	_, existing, err := s.GetStore().PeeringRead(nil, q)
+	if err != nil {
+		return fmt.Errorf("failed to read peering: %w", err)
+	}
+	if existing == nil || !existing.IsActive() {
+		return fmt.Errorf("peering does not exist or has been marked for deletion")
+	}
+
+	// Clone to avoid mutating the existing data
+	p := proto.Clone(existing).(*pbpeering.Peering)
+	p.PeerServerAddresses = addrs.GetAddresses()
+
+	req := &pbpeering.PeeringWriteRequest{
+		Peering: p,
+	}
+	return s.Backend.PeeringWrite(req)
+}
+
 func (s *Server) handleDelete(
 	peerName string,
 	partition string,

agent/grpc-external/services/peerstream/server.go

@@ -104,6 +104,7 @@ type Backend interface {
 	PeeringTrustBundleWrite(req *pbpeering.PeeringTrustBundleWriteRequest) error
 	CatalogRegister(req *structs.RegisterRequest) error
 	CatalogDeregister(req *structs.DeregisterRequest) error
+	PeeringWrite(req *pbpeering.PeeringWriteRequest) error
 }
 
 // StateStore provides a read-only interface for querying Peering data.

agent/grpc-external/services/peerstream/stream_test.go

@@ -126,7 +126,7 @@ func TestStreamResources_Server_LeaderBecomesFollower(t *testing.T) {
 
 	// Receive a subscription from a peer. This message arrives while the
 	// server is a leader and should work.
-	testutil.RunStep(t, "send subscription request to leader and consume its two requests", func(t *testing.T) {
+	testutil.RunStep(t, "send subscription request to leader and consume its three requests", func(t *testing.T) {
 		sub := &pbpeerstream.ReplicationMessage{
 			Payload: &pbpeerstream.ReplicationMessage_Open_{
 				Open: &pbpeerstream.ReplicationMessage_Open{
@@ -145,6 +145,10 @@ func TestStreamResources_Server_LeaderBecomesFollower(t *testing.T) {
 		msg2, err := client.Recv()
 		require.NoError(t, err)
 		require.NotEmpty(t, msg2)
+
+		msg3, err := client.Recv()
+		require.NoError(t, err)
+		require.NotEmpty(t, msg3)
 	})
 
 	// The ACK will be a new request but at this point the server is not the
@@ -1314,7 +1318,7 @@ func TestStreamResources_Server_KeepsConnectionOpenWithHeartbeat(t *testing.T) {
 
 // makeClient sets up a *MockClient with the initial subscription
 // message handshake.
-func makeClient(t *testing.T, srv pbpeerstream.PeerStreamServiceServer, peerID string) *MockClient {
+func makeClient(t *testing.T, srv *testServer, peerID string) *MockClient {
 	t.Helper()
 
 	client := NewMockClient(context.Background())
@@ -1326,7 +1330,7 @@ func makeClient(t *testing.T, srv pbpeerstream.PeerStreamServiceServer, peerID s
 		// Pass errors from server handler into ErrCh so that they can be seen by the client on Recv().
 		// This matches gRPC's behavior when an error is returned by a server.
 		if err := srv.StreamResources(client.ReplicationStream); err != nil {
-			errCh <- srv.StreamResources(client.ReplicationStream)
+			errCh <- err
 		}
 	}()
 
@@ -1345,8 +1349,15 @@ func makeClient(t *testing.T, srv pbpeerstream.PeerStreamServiceServer, peerID s
 	require.NoError(t, err)
 	receivedSub2, err := client.Recv()
 	require.NoError(t, err)
+	receivedSub3, err := client.Recv()
+	require.NoError(t, err)
 
-	// Issue a services and roots subscription pair to server
+	// This is required when the client subscribes to server address replication messages.
+	// We assert for the handler to be called at least once but the data doesn't matter.
+	srv.mockSnapshotHandler.expect("", 0, 0, nil)
+
+	// Issue services, roots, and server address subscription to server.
+	// Note that server address may not come as an initial message
 	for _, resourceURL := range []string{
 		pbpeerstream.TypeURLExportedService,
 		pbpeerstream.TypeURLPeeringTrustBundle,
@@ -1390,6 +1401,7 @@ func makeClient(t *testing.T, srv pbpeerstream.PeerStreamServiceServer, peerID s
 	got := []*pbpeerstream.ReplicationMessage{
 		receivedSub1,
 		receivedSub2,
+		receivedSub3,
 	}
 	prototest.AssertElementsMatch(t, expect, got)
 
@@ -1446,6 +1458,10 @@ func (b *testStreamBackend) PeeringSecretsWrite(req *pbpeering.SecretsWriteReque
 	return b.store.PeeringSecretsWrite(1, req)
 }
 
+func (b *testStreamBackend) PeeringWrite(req *pbpeering.PeeringWriteRequest) error {
+	return b.store.PeeringWrite(1, req)
+}
+
 // CatalogRegister mocks catalog registrations through Raft by copying the logic of FSM.applyRegister.
 func (b *testStreamBackend) CatalogRegister(req *structs.RegisterRequest) error {
 	return b.store.EnsureRegistration(1, req)
@@ -2734,11 +2750,16 @@ func requireEqualInstances(t *testing.T, expect, got structs.CheckServiceNodes)
 
 type testServer struct {
 	*Server
+
+	// mockSnapshotHandler is solely used for handling autopilot events
+	// which don't come from the state store.
+	mockSnapshotHandler *mockSnapshotHandler
 }
 
 func newTestServer(t *testing.T, configFn func(c *Config)) (*testServer, *state.Store) {
+	t.Helper()
 	publisher := stream.NewEventPublisher(10 * time.Second)
-	store := newStateStore(t, publisher)
+	store, handler := newStateStore(t, publisher)
 
 	ports := freeport.GetN(t, 1) // {grpc}
 
@@ -2776,6 +2797,7 @@ func newTestServer(t *testing.T, configFn func(c *Config)) (*testServer, *state.
 
 	return &testServer{
 		Server:              srv,
+		mockSnapshotHandler: handler,
 	}, store
 }