Add dropped alertmanagers to alertmanagers API (#3865)

docs/querying/api.md

@@ -356,9 +356,6 @@ $ curl http://localhost:9090/api/v1/targets
 
 ## Alertmanagers
 
-> This API is experimental as it is intended to be extended with Alertmanagers
-> dropped due to relabelling in the future.
-
 The following endpoint returns an overview of the current state of the
 Prometheus alertmanager discovery:
 
@@ -366,7 +363,7 @@ Prometheus alertmanager discovery:
 GET /api/v1/alertmanagers
 ```
 
-Currently only the active Alertmanagers are part of the response.
+Both the active and dropped Alertmanagers are part of the response.
 
 ```json
 $ curl http://localhost:9090/api/v1/alertmanagers
@@ -377,6 +374,11 @@ $ curl http://localhost:9090/api/v1/alertmanagers
       {
         "url": "http://127.0.0.1:9090/api/v1/alerts"
       }
+    ],
+    "droppedAlertmanagers": [
+      {
+        "url": "http://127.0.0.1:9093/api/v1/alerts"
+      }
     ]
   }
 }

notifier/notifier.go

@@ -419,6 +419,25 @@ func (n *Manager) Alertmanagers() []*url.URL {
 	return res
 }
 
+// DroppedAlertmanagers returns a slice of Alertmanager URLs.
+func (n *Manager) DroppedAlertmanagers() []*url.URL {
+	n.mtx.RLock()
+	amSets := n.alertmanagers
+	n.mtx.RUnlock()
+
+	var res []*url.URL
+
+	for _, ams := range amSets {
+		ams.mtx.RLock()
+		for _, dam := range ams.droppedAms {
+			res = append(res, dam.url())
+		}
+		ams.mtx.RUnlock()
+	}
+
+	return res
+}
+
 // sendAll sends the alerts to all configured Alertmanagers concurrently.
 // It returns true if the alerts could be sent successfully to at least one Alertmanager.
 func (n *Manager) sendAll(alerts ...*Alert) bool {
@@ -521,6 +540,7 @@ type alertmanagerSet struct {
 
 	mtx        sync.RWMutex
 	ams        []alertmanager
+	droppedAms []alertmanager
 	logger     log.Logger
 }
 
@@ -540,24 +560,28 @@ func newAlertmanagerSet(cfg *config.AlertmanagerConfig, logger log.Logger) (*ale
 // sync extracts a deduplicated set of Alertmanager endpoints from a list
 // of target groups definitions.
 func (s *alertmanagerSet) sync(tgs []*targetgroup.Group) {
-	all := []alertmanager{}
+	allAms := []alertmanager{}
+	allDroppedAms := []alertmanager{}
 
 	for _, tg := range tgs {
-		ams, err := alertmanagerFromGroup(tg, s.cfg)
+		ams, droppedAms, err := alertmanagerFromGroup(tg, s.cfg)
 		if err != nil {
 			level.Error(s.logger).Log("msg", "Creating discovered Alertmanagers failed", "err", err)
 			continue
 		}
-		all = append(all, ams...)
+		allAms = append(allAms, ams...)
+		allDroppedAms = append(allDroppedAms, droppedAms...)
 	}
 
 	s.mtx.Lock()
 	defer s.mtx.Unlock()
 	// Set new Alertmanagers and deduplicate them along their unique URL.
 	s.ams = []alertmanager{}
+	s.droppedAms = []alertmanager{}
+	s.droppedAms = append(s.droppedAms, allDroppedAms...)
 	seen := map[string]struct{}{}
 
-	for _, am := range all {
+	for _, am := range allAms {
 		us := am.url().String()
 		if _, ok := seen[us]; ok {
 			continue
@@ -578,8 +602,9 @@ func postPath(pre string) string {
 
 // alertmanagersFromGroup extracts a list of alertmanagers from a target group and an associcated
 // AlertmanagerConfig.
-func alertmanagerFromGroup(tg *targetgroup.Group, cfg *config.AlertmanagerConfig) ([]alertmanager, error) {
+func alertmanagerFromGroup(tg *targetgroup.Group, cfg *config.AlertmanagerConfig) ([]alertmanager, []alertmanager, error) {
 	var res []alertmanager
+	var droppedAlertManagers []alertmanager
 
 	for _, tlset := range tg.Targets {
 		lbls := make([]labels.Label, 0, len(tlset)+2+len(tg.Labels))
@@ -600,6 +625,7 @@ func alertmanagerFromGroup(tg *targetgroup.Group, cfg *config.AlertmanagerConfig
 
 		lset := relabel.Process(labels.New(lbls...), cfg.RelabelConfigs...)
 		if lset == nil {
+			droppedAlertManagers = append(droppedAlertManagers, alertmanagerLabels{lbls})
 			continue
 		}
 
@@ -627,13 +653,13 @@ func alertmanagerFromGroup(tg *targetgroup.Group, cfg *config.AlertmanagerConfig
 			case "https":
 				addr = addr + ":443"
 			default:
-				return nil, fmt.Errorf("invalid scheme: %q", cfg.Scheme)
+				return nil, nil, fmt.Errorf("invalid scheme: %q", cfg.Scheme)
 			}
 			lb.Set(model.AddressLabel, addr)
 		}
 
 		if err := config.CheckTargetAddress(model.LabelValue(addr)); err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 
 		// Meta labels are deleted after relabelling. Other internal labels propagate to
@@ -646,5 +672,5 @@ func alertmanagerFromGroup(tg *targetgroup.Group, cfg *config.AlertmanagerConfig
 
 		res = append(res, alertmanagerLabels{lset})
 	}
-	return res, nil
+	return res, droppedAlertManagers, nil
 }

notifier/notifier_test.go

@@ -442,7 +442,7 @@ func (a alertmanagerMock) url() *url.URL {
 
 func TestLabelSetNotReused(t *testing.T) {
 	tg := makeInputTargetGroup()
-	_, err := alertmanagerFromGroup(tg, &config.AlertmanagerConfig{})
+	_, _, err := alertmanagerFromGroup(tg, &config.AlertmanagerConfig{})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -503,6 +503,61 @@ alerting:
 
 }
 
+func TestDroppedAlertmanagers(t *testing.T) {
+	var tests = []struct {
+		in  *targetgroup.Group
+		out string
+	}{
+		{
+			in: &targetgroup.Group{
+				Targets: []model.LabelSet{
+					{
+						"__address__": "alertmanager:9093",
+					},
+				},
+			},
+			out: "http://alertmanager:9093/api/v1/alerts",
+		},
+	}
+
+	n := NewManager(&Options{}, nil)
+
+	cfg := &config.Config{}
+	s := `
+alerting:
+  alertmanagers:
+  - static_configs:
+    relabel_configs:
+      - source_labels: ['__address__']
+        regex: 'alertmanager:9093'
+        action: drop
+`
+	if err := yaml.Unmarshal([]byte(s), cfg); err != nil {
+		t.Fatalf("Unable to load YAML config: %s", err)
+	}
+
+	if err := n.ApplyConfig(cfg); err != nil {
+		t.Fatalf("Error Applying the config:%v", err)
+	}
+
+	tgs := make(map[string][]*targetgroup.Group)
+	for _, tt := range tests {
+
+		b, err := json.Marshal(cfg.AlertingConfig.AlertmanagerConfigs[0])
+		if err != nil {
+			t.Fatalf("Error creating config hash:%v", err)
+		}
+		tgs[fmt.Sprintf("%x", md5.Sum(b))] = []*targetgroup.Group{
+			tt.in,
+		}
+		n.reload(tgs)
+		res := n.DroppedAlertmanagers()[0].String()
+
+		testutil.Equals(t, res, tt.out)
+	}
+
+}
+
 func makeInputTargetGroup() *targetgroup.Group {
 	return &targetgroup.Group{
 		Targets: []model.LabelSet{

web/api/v1/api.go

@@ -87,6 +87,7 @@ type targetRetriever interface {
 
 type alertmanagerRetriever interface {
 	Alertmanagers() []*url.URL
+	DroppedAlertmanagers() []*url.URL
 }
 
 type response struct {
@@ -469,6 +470,7 @@ func (api *API) targets(r *http.Request) (interface{}, *apiError) {
 // AlertmanagerDiscovery has all the active Alertmanagers.
 type AlertmanagerDiscovery struct {
 	ActiveAlertmanagers  []*AlertmanagerTarget `json:"activeAlertmanagers"`
+	DroppedAlertmanagers []*AlertmanagerTarget `json:"droppedAlertmanagers"`
 }
 
 // AlertmanagerTarget has info on one AM.
@@ -478,12 +480,14 @@ type AlertmanagerTarget struct {
 
 func (api *API) alertmanagers(r *http.Request) (interface{}, *apiError) {
 	urls := api.alertmanagerRetriever.Alertmanagers()
-	ams := &AlertmanagerDiscovery{ActiveAlertmanagers: make([]*AlertmanagerTarget, len(urls))}
+	droppedURLS := api.alertmanagerRetriever.DroppedAlertmanagers()
-
+	ams := &AlertmanagerDiscovery{ActiveAlertmanagers: make([]*AlertmanagerTarget, len(urls)), DroppedAlertmanagers: make([]*AlertmanagerTarget, len(droppedURLS))}
 	for i, url := range urls {
 		ams.ActiveAlertmanagers[i] = &AlertmanagerTarget{URL: url.String()}
 	}
-
+	for i, url := range droppedURLS {
+		ams.DroppedAlertmanagers[i] = &AlertmanagerTarget{URL: url.String()}
+	}
 	return ams, nil
 }
 

web/api/v1/api_test.go

@@ -48,10 +48,26 @@ func (f targetRetrieverFunc) Targets() []*scrape.Target {
 	return f()
 }
 
-type alertmanagerRetrieverFunc func() []*url.URL
+type testAlertmanagerRetriever struct{}
 
-func (f alertmanagerRetrieverFunc) Alertmanagers() []*url.URL {
+func (t testAlertmanagerRetriever) Alertmanagers() []*url.URL {
-	return f()
+	return []*url.URL{
+		{
+			Scheme: "http",
+			Host:   "alertmanager.example.com:8080",
+			Path:   "/api/v1/alerts",
+		},
+	}
+}
+
+func (t testAlertmanagerRetriever) DroppedAlertmanagers() []*url.URL {
+	return []*url.URL{
+		{
+			Scheme: "http",
+			Host:   "dropped.alertmanager.example.com:8080",
+			Path:   "/api/v1/alerts",
+		},
+	}
 }
 
 var samplePrometheusCfg = config.Config{
@@ -100,13 +116,7 @@ func TestEndpoints(t *testing.T) {
 		}
 	})
 
-	ar := alertmanagerRetrieverFunc(func() []*url.URL {
+	var ar testAlertmanagerRetriever
-		return []*url.URL{{
-			Scheme: "http",
-			Host:   "alertmanager.example.com:8080",
-			Path:   "/api/v1/alerts",
-		}}
-	})
 
 	api := &API{
 		Queryable:             suite.Storage(),
@@ -447,6 +457,11 @@ func TestEndpoints(t *testing.T) {
 						URL: "http://alertmanager.example.com:8080/api/v1/alerts",
 					},
 				},
+				DroppedAlertmanagers: []*AlertmanagerTarget{
+					{
+						URL: "http://dropped.alertmanager.example.com:8080/api/v1/alerts",
+					},
+				},
 			},
 		},
 		{