Add a 'SilenceURL' for the alertmanager templates

The intention is that this URL can then be referenced from the HTML template in
the service to provide a handy link to set up a silence.

src/github.com/matrix-org/go-neb/services/alertmanager/alertmanager.go

@@ -12,6 +12,7 @@ import (
 	html "html/template"
 	"net/http"
 	text "text/template"
+	"strings"
 )
 
 // ServiceType of the Alertmanager service.
@@ -69,6 +70,7 @@ type WebhookNotification struct {
 		StartsAt     string            `json:"startsAt"`
 		EndsAt       string            `json:"endsAt"`
 		GeneratorURL string            `json:"generatorURL"`
+		SilenceURL   string
 	} `json:"alerts"`
 }
 
@@ -82,6 +84,18 @@ func (s *Service) OnReceiveWebhook(w http.ResponseWriter, req *http.Request, cli
 		return
 	}
 
+	// add the silence link for each alert
+	// see 'newSilenceFromAlertLabels' in
+	// https://github.com/prometheus/alertmanager/blob/master/ui/app/src/Views/SilenceForm/Parsing.elm
+	for i := range notif.Alerts {
+		alert := &notif.Alerts[i]
+		filters := []string{}
+		for label, val := range alert.Labels {
+			filters = append(filters, fmt.Sprintf("%s%%3D\"%s\"", label, val))
+		}
+		alert.SilenceURL = fmt.Sprintf("%s#silences/new?filter={%s}", notif.ExternalURL, strings.Join(filters, ",") )
+	}
+
 	for roomID, templates := range s.Rooms {
 		var msg interface{}
 		// we don't check whether the templates parse because we already did when storing them in the db

src/github.com/matrix-org/go-neb/services/alertmanager/alertmanager_test.go

@@ -0,0 +1,144 @@
+package alertmanager
+
+import (
+	"github.com/matrix-org/go-neb/database"
+	"github.com/matrix-org/go-neb/testutils"
+	"github.com/matrix-org/gomatrix"
+	"net/http"
+	"strings"
+	"fmt"
+	"encoding/json"
+	"io/ioutil"
+	"bytes"
+	"testing"
+	"github.com/matrix-org/go-neb/types"
+	"net/http/httptest"
+	"regexp"
+)
+
+func TestNotify(t *testing.T) {
+	database.SetServiceDB(&database.NopStorage{})
+
+	// Intercept message sending to Matrix and mock responses
+	msgs := []gomatrix.HTMLMessage{}
+	matrixTrans := struct{ testutils.MockTransport }{}
+	matrixTrans.RT = func(req *http.Request) (*http.Response, error) {
+		if !strings.Contains(req.URL.String(), "/send/m.room.message") {
+			return nil, fmt.Errorf("Unhandled URL: %s", req.URL.String())
+		}
+		var msg gomatrix.HTMLMessage
+		if err := json.NewDecoder(req.Body).Decode(&msg); err != nil {
+			return nil, fmt.Errorf("Failed to decode request JSON: %s", err)
+		}
+		msgs = append(msgs, msg)
+		return &http.Response{
+			StatusCode: 200,
+			Body:       ioutil.NopCloser(bytes.NewBufferString(`{"event_id":"$yup:event"}`)),
+		}, nil
+	}
+	matrixCli, _ := gomatrix.NewClient("https://hs", "@neb:hs", "its_a_secret")
+	matrixCli.Client = &http.Client{Transport: matrixTrans}
+
+	// create the service
+	html_template, err := json.Marshal(
+		`{{range .Alerts}}
+		{{index .Labels "severity" }} : {{- index .Labels "alertname" -}}
+		<a href="{{ .GeneratorURL }}">source</a>
+		<a href="{{ .SilenceURL }}">silence</a>
+		{{- end }}
+		`,
+    )
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+    text_template, err := json.Marshal(`{{range .Alerts}}{{index .Labels "alertname"}} {{end}}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+    config := fmt.Sprintf(`{
+		"rooms":{ "!testroom:id" : {
+			"text_template":%s,
+			"html_template":%s,
+			"msg_type":"m.text"
+		}}
+	}`, text_template, html_template,
+	)
+
+	srv, err := types.CreateService("id", "alertmanager", "@neb:hs", []byte(config))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// send a notification
+	req, err := http.NewRequest(
+		"POST", "", bytes.NewBufferString(`
+			{
+				"externalURL": "http://alertmanager",
+				 "alerts": [
+                    {
+                        "labels": {
+							"alertname": "alert 1",
+							"severity": "huge"
+                        },
+						"generatorURL": "http://x"
+                    },
+                    {
+                        "labels": {
+							"alertname": "alert 2",
+							"severity": "tiny"
+                        },
+						"generatorURL": "http://y"
+                    }
+				]
+            }
+		`),
+	)
+	if err != nil {
+		t.Fatalf("Failed to create webhook request: %s", err)
+	}
+	mockWriter := httptest.NewRecorder()
+	srv.OnReceiveWebhook(mockWriter, req, matrixCli)
+
+	// check response
+	if mockWriter.Code != 200 {
+		t.Fatalf("Expected response 200 OK, got %d", mockWriter.Code)
+	}
+	if len(msgs) != 1 {
+		t.Fatalf("Expected sent 1 msgs, sent %d", len(msgs))
+	}
+	msg := msgs[0]
+	if msg.MsgType != "m.text" {
+		t.Errorf("Wrong msgtype: got %s want m.text", msg.MsgType)
+	}
+
+	lines := strings.Split(msg.FormattedBody, "\n" )
+
+	// 	<a href="http://alertmanager#silences/new?filter=%7balertname%3D%22alert%202%22,severity%3D%22tiny%22%7d">silence</a>
+	silenceRegexp := regexp.MustCompile(`<a href="([^"]*)">silence</a>`)
+	matchedSilence := 0
+	for _, line := range lines {
+		if ! strings.Contains(line, "silence") {
+			continue
+		}
+
+		matchedSilence += 1
+		m := silenceRegexp.FindStringSubmatch(line)
+		if m == nil {
+			t.Errorf("silence line %s had bad format", line)
+		} else {
+			url := m[1]
+			expected := "http://alertmanager#silences/new?filter=%7balertname%3D%22alert%201%22,severity%3D%22huge%22%7d"
+			if url != expected {
+				t.Errorf("silence url: got %s, want %s", url, expected)
+			}
+		}
+		break
+	}
+
+	if matchedSilence == 0 {
+		t.Errorf("Did not find any silence lines")
+	}
+}