From 77de9bbe22aa1531185c7fe81089713a15420327 Mon Sep 17 00:00:00 2001
From: Freddy <freddygv@users.noreply.github.com>
Date: Wed, 12 Aug 2020 09:47:41 -0600
Subject: [PATCH] Notify alias checks when aliased service is [de]registered
 (#8456)

---
 agent/local/state.go      |  9 ++++++-
 agent/local/state_test.go | 53 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/agent/local/state.go b/agent/local/state.go
index 335721a5c..f6e396131 100644
--- a/agent/local/state.go
+++ b/agent/local/state.go
@@ -305,6 +305,8 @@ func (l *State) removeServiceLocked(id structs.ServiceID) error {
 		close(s.WatchCh)
 		s.WatchCh = nil
 	}
+
+	l.notifyIfAliased(id)
 	l.TriggerSyncChanges()
 	l.broadcastUpdateLocked()
 
@@ -379,6 +381,11 @@ func (l *State) setServiceStateLocked(s *ServiceState) {
 	if hasOld && old.WatchCh != nil {
 		close(old.WatchCh)
 	}
+	if !hasOld {
+		// The status of an alias check is updated if the alias service is added/removed
+		// Only try notify alias checks if service didn't already exist (!hasOld)
+		l.notifyIfAliased(key)
+	}
 
 	l.TriggerSyncChanges()
 	l.broadcastUpdateLocked()
@@ -1353,7 +1360,7 @@ func (l *State) syncNodeInfo() error {
 	}
 }
 
-// notifyIfAliased will notify waiters if this is a check for an aliased service
+// notifyIfAliased will notify waiters of changes to an aliased service
 func (l *State) notifyIfAliased(serviceID structs.ServiceID) {
 	if aliases, ok := l.checkAliases[serviceID]; ok && len(aliases) > 0 {
 		for _, notifyCh := range aliases {
diff --git a/agent/local/state_test.go b/agent/local/state_test.go
index c418bb948..4a9b7f8e7 100644
--- a/agent/local/state_test.go
+++ b/agent/local/state_test.go
@@ -1912,6 +1912,59 @@ func TestAgent_AliasCheck(t *testing.T) {
 	}
 }
 
+func TestAgent_AliasCheck_ServiceNotification(t *testing.T) {
+	t.Parallel()
+
+	require := require.New(t)
+	cfg := config.DefaultRuntimeConfig(`bind_addr = "127.0.0.1" data_dir = "dummy"`)
+	l := local.NewState(agent.LocalConfig(cfg), nil, new(token.Store))
+	l.TriggerSyncChanges = func() {}
+
+	// Add an alias check for service s1
+	notifyCh := make(chan struct{}, 1)
+	require.NoError(l.AddAliasCheck(structs.NewCheckID(types.CheckID("a1"), nil), structs.NewServiceID("s1", nil), notifyCh))
+
+	// Add aliased service, s1, and verify we get notified
+	require.NoError(l.AddService(&structs.NodeService{Service: "s1"}, ""))
+	select {
+	case <-notifyCh:
+	default:
+		t.Fatal("notify not received")
+	}
+
+	// Re-adding same service should not lead to a notification
+	require.NoError(l.AddService(&structs.NodeService{Service: "s1"}, ""))
+	select {
+	case <-notifyCh:
+		t.Fatal("notify received")
+	default:
+	}
+
+	// Add different service and verify we do not get notified
+	require.NoError(l.AddService(&structs.NodeService{Service: "s2"}, ""))
+	select {
+	case <-notifyCh:
+		t.Fatal("notify received")
+	default:
+	}
+
+	// Delete service and verify we get notified
+	require.NoError(l.RemoveService(structs.NewServiceID("s1", nil)))
+	select {
+	case <-notifyCh:
+	default:
+		t.Fatal("notify not received")
+	}
+
+	// Delete different service and verify we do not get notified
+	require.NoError(l.RemoveService(structs.NewServiceID("s2", nil)))
+	select {
+	case <-notifyCh:
+		t.Fatal("notify received")
+	default:
+	}
+}
+
 func TestAgent_sendCoordinate(t *testing.T) {
 	t.Parallel()
 	a := agent.StartTestAgent(t, agent.TestAgent{Overrides: `