test that Grafana templates are usable in alerts

pkg/alertmanager/alertmanager_test.go

@@ -589,7 +589,7 @@ route:
 					"alertname": model.LabelValue("Alert-1"),
 					"a":         "b",
 				},
-				Annotations:  model.LabelSet{"foo": "bar"},
+				Annotations:  model.LabelSet{"templates": `{{ template "test" . }}`},
 				StartsAt:     now,
 				EndsAt:       now.Add(5 * time.Minute),
 				GeneratorURL: "http://example.com/prometheus",
@@ -621,3 +621,80 @@ route:
 	assert.Zero(t, result[1].Integrations[0].LastNotifyAttempt)
 	assert.Equal(t, "", result[1].Integrations[0].LastNotifyAttemptError)
 }
+
+func TestGrafanaAlertmanagerTemplates(t *testing.T) {
+	am, err := New(&Config{
+		UserID:            "test",
+		Logger:            log.NewNopLogger(),
+		Limits:            &mockAlertManagerLimits{},
+		Features:          featurecontrol.NoopFlags{},
+		TenantDataDir:     t.TempDir(),
+		ExternalURL:       &url.URL{Path: "/am"},
+		ShardingEnabled:   true,
+		Store:             prepareInMemoryAlertStore(),
+		Replicator:        &stubReplicator{},
+		ReplicationFactor: 1,
+		// We have to set this interval non-zero, though we don't need the persister to do anything.
+		PersisterConfig: PersisterConfig{Interval: time.Hour},
+	}, prometheus.NewPedanticRegistry())
+	require.NoError(t, err)
+	defer am.StopAndWait()
+
+	// The webhook message should contain the executed Grafana template.
+	var got struct {
+		Message string `json:"message"`
+	}
+	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewDecoder(r.Body).Decode(&got)
+		defer func() {
+			require.NoError(t, r.Body.Close())
+		}()
+	}))
+	defer s.Close()
+
+	cfgRaw := fmt.Sprintf(`{
+            "route": {
+                "receiver": "test_receiver",
+                "group_by": ["alertname"]
+            },
+            "receivers": [{
+                "name": "test_receiver",
+                "grafana_managed_receiver_configs": [{
+                    "uid": "",
+                    "name": "webhook test",
+                    "type": "webhook",
+                    "disableResolveMessage": true,
+                    "settings": {
+                        "url": %q,
+                        "message": %q
+                    },
+                }]
+            }],
+        }`, s.URL, `{{ template "test" . }}`)
+
+	cfg, err := definition.LoadCompat([]byte(cfgRaw))
+	require.NoError(t, err)
+	expMessage := "This is a test template"
+	testTemplate := alertingTemplates.TemplateDefinition{
+		Name:     "test",
+		Template: fmt.Sprintf(`{{ define "test" -}} %s {{- end }}`, expMessage),
+	}
+	require.NoError(t, am.ApplyConfig(cfg, []alertingTemplates.TemplateDefinition{testTemplate}, cfgRaw, &url.URL{}, nil))
+
+	now := time.Now()
+	alert := types.Alert{
+		Alert: model.Alert{
+			Labels: model.LabelSet{
+				"alertname": model.LabelValue("test-alert"),
+			},
+			StartsAt: now.Add(-5 * time.Minute),
+			EndsAt:   now.Add(5 * time.Minute),
+		},
+		UpdatedAt: now,
+	}
+	require.NoError(t, am.alerts.Put(&alert))
+	require.Equal(t, am.templates[0], testTemplate)
+	require.Eventually(t, func() bool {
+		return got.Message == expMessage
+	}, 5*time.Second, 100*time.Millisecond)
+}