agent: avoid reverting any check updates that occur while a service is being added or the config is reloaded (#6144)

agent/agent.go

@@ -457,7 +457,7 @@ func (a *Agent) Start() error {
 	if err := a.loadProxies(c); err != nil {
 		return err
 	}
-	if err := a.loadChecks(c); err != nil {
+	if err := a.loadChecks(c, nil); err != nil {
 		return err
 	}
 	if err := a.loadMetadata(c); err != nil {
@@ -2109,10 +2109,10 @@ func (a *Agent) addServiceInternal(service *structs.NodeService, chkTypes []*str
 	a.PauseSync()
 	defer a.ResumeSync()
 
-	// Take a snapshot of the current state of checks (if any), and
-	// restore them before resuming anti-entropy.
+	// Take a snapshot of the current state of checks (if any), and when adding
+	// a check that already existed carry over the state before resuming
+	// anti-entropy.
 	snap := a.snapshotCheckState()
-	defer a.restoreCheckState(snap)
 
 	var checks []*structs.HealthCheck
 
@@ -2143,6 +2143,13 @@ func (a *Agent) addServiceInternal(service *structs.NodeService, chkTypes []*str
 			check.Status = chkType.Status
 		}
 
+		// Restore the fields from the snapshot.
+		prev, ok := snap[check.CheckID]
+		if ok {
+			check.Output = prev.Output
+			check.Status = prev.Status
+		}
+
 		checks = append(checks, check)
 	}
 
@@ -3346,10 +3353,17 @@ func (a *Agent) unloadServices() error {
 
 // loadChecks loads check definitions and/or persisted check definitions from
 // disk and re-registers them with the local agent.
-func (a *Agent) loadChecks(conf *config.RuntimeConfig) error {
+func (a *Agent) loadChecks(conf *config.RuntimeConfig, snap map[types.CheckID]*structs.HealthCheck) error {
 	// Register the checks from config
 	for _, check := range conf.Checks {
 		health := check.HealthCheck(conf.NodeName)
+
+		// Restore the fields from the snapshot.
+		if prev, ok := snap[health.CheckID]; ok {
+			health.Output = prev.Output
+			health.Status = prev.Status
+		}
+
 		chkType := check.CheckType()
 		if err := a.addCheckLocked(health, chkType, false, check.Token, ConfigSourceLocal); err != nil {
 			return fmt.Errorf("Failed to register check '%s': %v %v", check.Name, err, check)
@@ -3406,6 +3420,12 @@ func (a *Agent) loadChecks(conf *config.RuntimeConfig) error {
 			// services into the active pool
 			p.Check.Status = api.HealthCritical
 
+			// Restore the fields from the snapshot.
+			if prev, ok := snap[p.Check.CheckID]; ok {
+				p.Check.Output = prev.Output
+				p.Check.Status = prev.Status
+			}
+
 			if err := a.addCheckLocked(p.Check, p.ChkType, false, p.Token, ConfigSourceLocal); err != nil {
 				// Purge the check if it is unable to be restored.
 				a.logger.Printf("[WARN] agent: Failed to restore check %q: %s",
@@ -3634,15 +3654,6 @@ func (a *Agent) snapshotCheckState() map[types.CheckID]*structs.HealthCheck {
 	return a.State.Checks()
 }
 
-// restoreCheckState is used to reset the health state based on a snapshot.
-// This is done after we finish the reload to avoid any unnecessary flaps
-// in health state and potential session invalidations.
-func (a *Agent) restoreCheckState(snap map[types.CheckID]*structs.HealthCheck) {
-	for id, check := range snap {
-		a.State.UpdateCheck(id, check.Status, check.Output)
-	}
-}
-
 // loadMetadata loads node metadata fields from the agent config and
 // updates them on the local agent.
 func (a *Agent) loadMetadata(conf *config.RuntimeConfig) error {
@@ -3765,9 +3776,9 @@ func (a *Agent) ReloadConfig(newCfg *config.RuntimeConfig) error {
 	a.stateLock.Lock()
 	defer a.stateLock.Unlock()
 
-	// Snapshot the current state, and restore it afterwards
+	// Snapshot the current state, and use that to initialize the checks when
+	// they are recreated.
 	snap := a.snapshotCheckState()
-	defer a.restoreCheckState(snap)
 
 	// First unload all checks, services, and metadata. This lets us begin the reload
 	// with a clean slate.
@@ -3798,7 +3809,7 @@ func (a *Agent) ReloadConfig(newCfg *config.RuntimeConfig) error {
 	if err := a.loadProxies(newCfg); err != nil {
 		return fmt.Errorf("Failed reloading proxies: %s", err)
 	}
-	if err := a.loadChecks(newCfg); err != nil {
+	if err := a.loadChecks(newCfg, snap); err != nil {
 		return fmt.Errorf("Failed reloading checks: %s", err)
 	}
 	if err := a.loadMetadata(newCfg); err != nil {

agent/agent_test.go

@@ -500,6 +500,62 @@ func TestAgent_AddService(t *testing.T) {
 	}
 }
 
+func TestAgent_AddServices_AliasUpdateCheckNotReverted(t *testing.T) {
+	t.Parallel()
+	a := NewTestAgent(t, t.Name(), `
+		node_name = "node1"
+	`)
+	defer a.Shutdown()
+
+	// It's tricky to get an UpdateCheck call to be timed properly so it lands
+	// right in the middle of an addServiceInternal call so we cheat a bit and
+	// rely upon alias checks to do that work for us.  We add enough services
+	// that probabilistically one of them is going to end up properly in the
+	// critical section.
+	//
+	// The first number I picked here (10) surprisingly failed every time prior
+	// to PR #6144 solving the underlying problem.
+	const numServices = 10
+
+	services := make([]*structs.ServiceDefinition, numServices)
+	checkIDs := make([]types.CheckID, numServices)
+	for i := 0; i < numServices; i++ {
+		name := fmt.Sprintf("web-%d", i)
+
+		services[i] = &structs.ServiceDefinition{
+			ID:   name,
+			Name: name,
+			Port: 8080 + i,
+			Checks: []*structs.CheckType{
+				&structs.CheckType{
+					Name:         "alias-for-fake-service",
+					AliasService: "fake",
+				},
+			},
+		}
+
+		checkIDs[i] = types.CheckID("service:" + name)
+	}
+
+	// Add all of the services quickly as you might do from config file snippets.
+	for _, service := range services {
+		ns := service.NodeService()
+
+		chkTypes, err := service.CheckTypes()
+		require.NoError(t, err)
+
+		require.NoError(t, a.AddService(ns, chkTypes, false, service.Token, ConfigSourceLocal))
+	}
+
+	retry.Run(t, func(r *retry.R) {
+		gotChecks := a.State.Checks()
+		for id, check := range gotChecks {
+			require.Equal(r, "passing", check.Status, "check %q is wrong", id)
+			require.Equal(r, "No checks found.", check.Output, "check %q is wrong", id)
+		}
+	})
+}
+
 func TestAgent_AddServiceNoExec(t *testing.T) {
 	t.Parallel()
 	a := NewTestAgent(t, t.Name(), `
@@ -2965,14 +3021,11 @@ func TestAgent_checkStateSnapshot(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	// Reload the checks
-	if err := a.loadChecks(a.Config); err != nil {
+	// Reload the checks and restore the snapshot.
+	if err := a.loadChecks(a.Config, snap); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
-	// Restore the state
-	a.restoreCheckState(snap)
-
 	// Search for the check
 	out, ok := a.State.Checks()[check1.CheckID]
 	if !ok {
@@ -3010,7 +3063,7 @@ func TestAgent_loadChecks_checkFails(t *testing.T) {
 	}
 
 	// Try loading the checks from the persisted files
-	if err := a.loadChecks(a.Config); err != nil {
+	if err := a.loadChecks(a.Config, nil); err != nil {
 		t.Fatalf("err: %s", err)
 	}