Route different alerts to different alertmanagers

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

config/config.go

@@ -823,6 +823,8 @@ type AlertmanagerConfig struct {
 
 	// List of Alertmanager relabel configurations.
 	RelabelConfigs []*relabel.Config `yaml:"relabel_configs,omitempty"`
+	// Relabel alerts before sending to the specific alertmanager.
+	AlertRelabelConfigs []*relabel.Config `yaml:"alert_relabel_configs,omitempty"`
 }
 
 // SetDirectory joins any relative file paths with dir.
@@ -858,6 +860,12 @@ func (c *AlertmanagerConfig) UnmarshalYAML(unmarshal func(interface{}) error) er
 		}
 	}
 
+	for _, rlcfg := range c.AlertRelabelConfigs {
+		if rlcfg == nil {
+			return errors.New("empty or null Alertmanager alert relabeling rule")
+		}
+	}
+
 	return nil
 }
 

notifier/notifier.go

@@ -349,7 +349,7 @@ func (n *Manager) Send(alerts ...*Alert) {
 	n.mtx.Lock()
 	defer n.mtx.Unlock()
 
-	alerts = n.relabelAlerts(alerts)
+	alerts = relabelAlerts(n.opts.RelabelConfigs, n.opts.ExternalLabels, alerts)
 	if len(alerts) == 0 {
 		return
 	}
@@ -377,20 +377,21 @@ func (n *Manager) Send(alerts ...*Alert) {
 	n.setMore()
 }
 
-// Attach external labels and process relabelling rules.
-func (n *Manager) relabelAlerts(alerts []*Alert) []*Alert {
+func relabelAlerts(relabelConfigs []*relabel.Config, externalLabels labels.Labels, alerts []*Alert) []*Alert {
 	lb := labels.NewBuilder(labels.EmptyLabels())
 	var relabeledAlerts []*Alert
 
 	for _, a := range alerts {
 		lb.Reset(a.Labels)
-		n.opts.ExternalLabels.Range(func(l labels.Label) {
-			if a.Labels.Get(l.Name) == "" {
-				lb.Set(l.Name, l.Value)
-			}
-		})
+		if externalLabels.Len() > 0 {
+			externalLabels.Range(func(l labels.Label) {
+				if a.Labels.Get(l.Name) == "" {
+					lb.Set(l.Name, l.Value)
+				}
+			})
+		}
 
-		keep := relabel.ProcessBuilder(lb, n.opts.RelabelConfigs...)
+		keep := relabel.ProcessBuilder(lb, relabelConfigs...)
 		if !keep {
 			continue
 		}
@@ -472,17 +473,30 @@ func (n *Manager) sendAll(alerts ...*Alert) bool {
 	)
 	for _, ams := range amSets {
 		var (
-			payload []byte
-			err     error
+			payload  []byte
+			err      error
+			amAlerts = alerts
 		)
 
 		ams.mtx.RLock()
 
+		if len(ams.cfg.AlertRelabelConfigs) > 0 {
+			amAlerts = relabelAlerts(ams.cfg.AlertRelabelConfigs, labels.Labels{}, alerts)
+			// TODO(nabokihms): figure out the right way to cache marshalled alerts.
+			//   Now it works well only for happy cases.
+			v1Payload = nil
+			v2Payload = nil
+
+			if len(amAlerts) == 0 {
+				continue
+			}
+		}
+
 		switch ams.cfg.APIVersion {
 		case config.AlertmanagerAPIVersionV1:
 			{
 				if v1Payload == nil {
-					v1Payload, err = json.Marshal(alerts)
+					v1Payload, err = json.Marshal(amAlerts)
 					if err != nil {
 						level.Error(n.logger).Log("msg", "Encoding alerts for Alertmanager API v1 failed", "err", err)
 						ams.mtx.RUnlock()
@@ -495,7 +509,7 @@ func (n *Manager) sendAll(alerts ...*Alert) bool {
 		case config.AlertmanagerAPIVersionV2:
 			{
 				if v2Payload == nil {
-					openAPIAlerts := alertsToOpenAPIAlerts(alerts)
+					openAPIAlerts := alertsToOpenAPIAlerts(amAlerts)
 
 					v2Payload, err = json.Marshal(openAPIAlerts)
 					if err != nil {
@@ -526,13 +540,13 @@ func (n *Manager) sendAll(alerts ...*Alert) bool {
 
 			go func(client *http.Client, url string) {
 				if err := n.sendOne(ctx, client, url, payload); err != nil {
-					level.Error(n.logger).Log("alertmanager", url, "count", len(alerts), "msg", "Error sending alert", "err", err)
+					level.Error(n.logger).Log("alertmanager", url, "count", len(amAlerts), "msg", "Error sending alert", "err", err)
 					n.metrics.errors.WithLabelValues(url).Inc()
 				} else {
 					numSuccess.Inc()
 				}
 				n.metrics.latency.WithLabelValues(url).Observe(time.Since(begin).Seconds())
-				n.metrics.sent.WithLabelValues(url).Add(float64(len(alerts)))
+				n.metrics.sent.WithLabelValues(url).Add(float64(len(amAlerts)))
 
 				wg.Done()
 			}(ams.client, am.url().String())

notifier/notifier_test.go

@@ -98,6 +98,41 @@ func alertsEqual(a, b []*Alert) error {
 	return nil
 }
 
+func newTestHTTPServerBuilder(expected *[]*Alert, errc chan<- error, u, p string, status *atomic.Int32) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var err error
+		defer func() {
+			if err == nil {
+				return
+			}
+			select {
+			case errc <- err:
+			default:
+			}
+		}()
+		user, pass, _ := r.BasicAuth()
+		if user != u || pass != p {
+			err = fmt.Errorf("unexpected user/password: %s/%s != %s/%s", user, pass, u, p)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+
+		b, err := io.ReadAll(r.Body)
+		if err != nil {
+			err = fmt.Errorf("error reading body: %v", err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+
+		var alerts []*Alert
+		err = json.Unmarshal(b, &alerts)
+		if err == nil {
+			err = alertsEqual(*expected, alerts)
+		}
+		w.WriteHeader(int(status.Load()))
+	}))
+}
+
 func TestHandlerSendAll(t *testing.T) {
 	var (
 		errc             = make(chan error, 1)
@@ -107,42 +142,8 @@ func TestHandlerSendAll(t *testing.T) {
 	status1.Store(int32(http.StatusOK))
 	status2.Store(int32(http.StatusOK))
 
-	newHTTPServer := func(u, p string, status *atomic.Int32) *httptest.Server {
-		return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			var err error
-			defer func() {
-				if err == nil {
-					return
-				}
-				select {
-				case errc <- err:
-				default:
-				}
-			}()
-			user, pass, _ := r.BasicAuth()
-			if user != u || pass != p {
-				err = fmt.Errorf("unexpected user/password: %s/%s != %s/%s", user, pass, u, p)
-				w.WriteHeader(http.StatusInternalServerError)
-				return
-			}
-
-			b, err := io.ReadAll(r.Body)
-			if err != nil {
-				err = fmt.Errorf("error reading body: %w", err)
-				w.WriteHeader(http.StatusInternalServerError)
-				return
-			}
-
-			var alerts []*Alert
-			err = json.Unmarshal(b, &alerts)
-			if err == nil {
-				err = alertsEqual(expected, alerts)
-			}
-			w.WriteHeader(int(status.Load()))
-		}))
-	}
-	server1 := newHTTPServer("prometheus", "testing_password", &status1)
-	server2 := newHTTPServer("", "", &status2)
+	server1 := newTestHTTPServerBuilder(&expected, errc, "prometheus", "testing_password", &status1)
+	server2 := newTestHTTPServerBuilder(&expected, errc, "", "", &status2)
 	defer server1.Close()
 	defer server2.Close()
 
@@ -213,6 +214,90 @@ func TestHandlerSendAll(t *testing.T) {
 	checkNoErr()
 }
 
+func TestHandlerSendAllRemapPerAm(t *testing.T) {
+	var (
+		errc      = make(chan error, 1)
+		expected1 = make([]*Alert, 0, maxBatchSize)
+		expected2 = make([]*Alert, 0, maxBatchSize)
+
+		status1, status2 atomic.Int32
+	)
+	status1.Store(int32(http.StatusOK))
+	status2.Store(int32(http.StatusOK))
+
+	server1 := newTestHTTPServerBuilder(&expected1, errc, "", "", &status1)
+	server2 := newTestHTTPServerBuilder(&expected2, errc, "", "", &status2)
+
+	defer server1.Close()
+	defer server2.Close()
+
+	h := NewManager(&Options{}, nil)
+	h.alertmanagers = make(map[string]*alertmanagerSet)
+
+	am1Cfg := config.DefaultAlertmanagerConfig
+	am1Cfg.Timeout = model.Duration(time.Second)
+
+	am2Cfg := config.DefaultAlertmanagerConfig
+	am2Cfg.Timeout = model.Duration(time.Second)
+	am2Cfg.AlertRelabelConfigs = []*relabel.Config{
+		{
+			SourceLabels: model.LabelNames{"alertnamedrop"},
+			Action:       "drop",
+			Regex:        relabel.MustNewRegexp(".+"),
+		},
+	}
+
+	h.alertmanagers["1"] = &alertmanagerSet{
+		ams: []alertmanager{
+			alertmanagerMock{
+				urlf: func() string { return server1.URL },
+			},
+		},
+		cfg: &am1Cfg,
+	}
+
+	h.alertmanagers["2"] = &alertmanagerSet{
+		ams: []alertmanager{
+			alertmanagerMock{
+				urlf: func() string { return server2.URL },
+			},
+		},
+		cfg: &am2Cfg,
+	}
+
+	for i := range make([]struct{}, maxBatchSize/2) {
+		h.queue = append(h.queue, &Alert{
+			Labels: labels.FromStrings("alertname", fmt.Sprintf("%d", i)),
+		})
+		h.queue = append(h.queue, &Alert{
+			Labels: labels.FromStrings("alertnamedrop", fmt.Sprintf("%d", i)),
+		})
+
+		expected1 = append(expected1, &Alert{
+			Labels: labels.FromStrings("alertname", fmt.Sprintf("%d", i)),
+		})
+		expected1 = append(expected1, &Alert{
+			Labels: labels.FromStrings("alertnamedrop", fmt.Sprintf("%d", i)),
+		})
+
+		expected2 = append(expected2, &Alert{
+			Labels: labels.FromStrings("alertname", fmt.Sprintf("%d", i)),
+		})
+	}
+
+	checkNoErr := func() {
+		t.Helper()
+		select {
+		case err := <-errc:
+			require.NoError(t, err)
+		default:
+		}
+	}
+
+	require.True(t, h.sendAll(h.queue...), "all sends failed unexpectedly")
+	checkNoErr()
+}
+
 func TestCustomDo(t *testing.T) {
 	const testURL = "http://testurl.com/"
 	const testBody = "testbody"