AlertingNG: Notification channel for emails (#31768)

* Email notification channel in ngalert

Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>

* Use existing templating system

Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>

* Update template and add unit tests

Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>

pkg/services/ngalert/notifier/channels/email.go

@@ -0,0 +1,92 @@
+package channels
+
+import (
+	"context"
+	"net/url"
+
+	gokit_log "github.com/go-kit/kit/log"
+	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/grafana/grafana/pkg/models"
+	"github.com/grafana/grafana/pkg/services/alerting"
+	old_notifiers "github.com/grafana/grafana/pkg/services/alerting/notifiers"
+	"github.com/grafana/grafana/pkg/util"
+
+	"github.com/grafana/grafana/pkg/bus"
+	"github.com/prometheus/alertmanager/notify"
+	"github.com/prometheus/alertmanager/template"
+	"github.com/prometheus/alertmanager/types"
+	"github.com/prometheus/common/model"
+)
+
+// EmailNotifier is responsible for sending
+// alert notifications over email.
+type EmailNotifier struct {
+	old_notifiers.NotifierBase
+	Addresses   []string
+	SingleEmail bool
+	log         log.Logger
+	externalUrl *url.URL
+}
+
+// NewEmailNotifier is the constructor function
+// for the EmailNotifier.
+func NewEmailNotifier(model *models.AlertNotification) (*EmailNotifier, error) {
+	addressesString := model.Settings.Get("addresses").MustString()
+	singleEmail := model.Settings.Get("singleEmail").MustBool(false)
+
+	if addressesString == "" {
+		return nil, alerting.ValidationError{Reason: "Could not find addresses in settings"}
+	}
+
+	// split addresses with a few different ways
+	addresses := util.SplitEmails(addressesString)
+
+	// TODO: remove this URL hack and add an actual external URL.
+	u, err := url.Parse("http://localhost")
+	if err != nil {
+		return nil, err
+	}
+
+	return &EmailNotifier{
+		NotifierBase: old_notifiers.NewNotifierBase(model),
+		Addresses:    addresses,
+		SingleEmail:  singleEmail,
+		log:          log.New("alerting.notifier.email"),
+		externalUrl:  u,
+	}, nil
+}
+
+// Notify sends the alert notification.
+func (en *EmailNotifier) Notify(ctx context.Context, as ...*types.Alert) error {
+	// TODO(codesome): make sure the receiver name is added in the ctx before calling this.
+	ctx = notify.WithReceiverName(ctx, "email-notification-channel") // Dummy.
+	// TODO(codesome): make sure the group labels is added in the ctx before calling this.
+	ctx = notify.WithGroupLabels(ctx, model.LabelSet{}) // Dummy.
+
+	// We only need ExternalURL from this template object. This hack should go away with https://github.com/prometheus/alertmanager/pull/2508.
+	data := notify.GetTemplateData(ctx, &template.Template{ExternalURL: en.externalUrl}, as, gokit_log.NewNopLogger())
+
+	cmd := &models.SendEmailCommandSync{
+		SendEmailCommand: models.SendEmailCommand{
+			Subject: "TODO",
+			Data: map[string]interface{}{
+				"Title":             "TODO",
+				"Subject":           "TODO",
+				"Receiver":          data.Receiver,
+				"Status":            data.Status,
+				"Alerts":            data.Alerts,
+				"GroupLabels":       data.GroupLabels,
+				"CommonLabels":      data.CommonLabels,
+				"CommonAnnotations": data.CommonAnnotations,
+				"ExternalURL":       data.ExternalURL,
+				"RuleUrl":           "TODO",
+				"AlertPageUrl":      "TODO",
+			},
+			To:          en.Addresses,
+			SingleEmail: en.SingleEmail,
+			Template:    "ng_alert_notification.html",
+		},
+	}
+
+	return bus.DispatchCtx(ctx, cmd)
+}

pkg/services/ngalert/notifier/channels/email_test.go

@@ -0,0 +1,59 @@
+package channels
+
+import (
+	"testing"
+
+	"github.com/grafana/grafana/pkg/components/simplejson"
+	"github.com/grafana/grafana/pkg/models"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEmailNotifier(t *testing.T) {
+	t.Run("empty settings should return error", func(t *testing.T) {
+		json := `{ }`
+
+		settingsJSON, _ := simplejson.NewJson([]byte(json))
+		model := &models.AlertNotification{
+			Name:     "ops",
+			Type:     "email",
+			Settings: settingsJSON,
+		}
+
+		_, err := NewEmailNotifier(model)
+		require.Error(t, err)
+	})
+
+	t.Run("from settings", func(t *testing.T) {
+		json := `{"addresses": "ops@grafana.org"}`
+		settingsJSON, err := simplejson.NewJson([]byte(json))
+		require.NoError(t, err)
+
+		emailNotifier, err := NewEmailNotifier(&models.AlertNotification{
+			Name:     "ops",
+			Type:     "email",
+			Settings: settingsJSON,
+		})
+
+		require.NoError(t, err)
+		require.Equal(t, "ops", emailNotifier.Name)
+		require.Equal(t, "email", emailNotifier.Type)
+		require.Equal(t, []string{"ops@grafana.org"}, emailNotifier.Addresses)
+	})
+
+	t.Run("from settings with two emails", func(t *testing.T) {
+		json := `{"addresses": "ops@grafana.org;dev@grafana.org"}`
+		settingsJSON, err := simplejson.NewJson([]byte(json))
+		require.NoError(t, err)
+
+		emailNotifier, err := NewEmailNotifier(&models.AlertNotification{
+			Name:     "ops",
+			Type:     "email",
+			Settings: settingsJSON,
+		})
+
+		require.NoError(t, err)
+		require.Equal(t, "ops", emailNotifier.Name)
+		require.Equal(t, "email", emailNotifier.Type)
+		require.Equal(t, []string{"ops@grafana.org", "dev@grafana.org"}, emailNotifier.Addresses)
+	})
+}