Email: Allow configuration of content types for email notifications (#34530)

* Alerting: Allow configuration of content types for email notifications

* Fix lint error

* Improves email templates

* Improve configuration documentation

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Improve code comments

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Improve configuration documentation

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Improve email template

* Remove unnecessary predeclaration

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Adds handling for unrecognized content type

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Move utility function outside of util package

* Fixes syntax

* Remove unused package

* Fix lint error

* improve email templates

* Fix test

* Alerting: Allow configuration of content types for email notifications

* Fix lint error

* Improves email templates

* Improve configuration documentation

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Improve code comments

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Improve configuration documentation

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Improve email template

* Remove unnecessary predeclaration

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Adds handling for unrecognized content type

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Move utility function outside of util package

* Fixes syntax

* Remove unused package

* Fix lint error

* improve email templates

* Fix test

* Fix comment style

Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>

* Fix template formatting

* Add test and improve error handling

* Fix test

* Fix formatting

* Fix formatting

* Improve documentation and regenerates txt template

* Update docs/sources/administration/configuration.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

Co-authored-by: Djairho Geuens <djairho.geuens@ae.be>
Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

pkg/api/org_invite.go

@@ -69,7 +69,7 @@ func AddOrgInvite(c *models.ReqContext, inviteDto dtos.AddInviteForm) response.R
 	if inviteDto.SendEmail && util.IsEmail(inviteDto.LoginOrEmail) {
 		emailCmd := models.SendEmailCommand{
 			To:       []string{inviteDto.LoginOrEmail},
-			Template: "new_user_invite.html",
+			Template: "new_user_invite",
 			Data: map[string]interface{}{
 				"Name":      util.StringsFallback2(cmd.Name, cmd.Email),
 				"OrgName":   c.OrgName,
@@ -111,7 +111,7 @@ func inviteExistingUserToOrg(c *models.ReqContext, user *models.User, inviteDto
 	if inviteDto.SendEmail && util.IsEmail(user.Email) {
 		emailCmd := models.SendEmailCommand{
 			To:       []string{user.Email},
-			Template: "invited_to_org.html",
+			Template: "invited_to_org",
 			Data: map[string]interface{}{
 				"Name":      user.NameOrFallback(),
 				"OrgName":   c.OrgName,

pkg/models/notifications.go

@@ -11,7 +11,7 @@ type SendEmailAttachFile struct {
 	Content []byte
 }
 
-// SendEmailCommand is command for sending emails
+// SendEmailCommand is the command for sending emails
 type SendEmailCommand struct {
 	To            []string
 	SingleEmail   bool
@@ -24,7 +24,7 @@ type SendEmailCommand struct {
 	AttachedFiles []*SendEmailAttachFile
 }
 
-// SendEmailCommandSync is command for sending emails in sync
+// SendEmailCommandSync is the command for sending emails synchronously
 type SendEmailCommandSync struct {
 	SendEmailCommand
 }

pkg/services/alerting/notifiers/email.go

@@ -100,7 +100,7 @@ func (en *EmailNotifier) Notify(evalContext *alerting.EvalContext) error {
 			},
 			To:            en.Addresses,
 			SingleEmail:   en.SingleEmail,
-			Template:      "alert_notification.html",
+			Template:      "alert_notification",
 			EmbeddedFiles: []string{},
 		},
 	}

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

@@ -96,7 +96,7 @@ func (en *EmailNotifier) Notify(ctx context.Context, as ...*types.Alert) (bool,
 			},
 			To:          en.Addresses,
 			SingleEmail: en.SingleEmail,
-			Template:    "ng_alert_notification.html",
+			Template:    "ng_alert_notification",
 		},
 	}
 

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

@@ -80,7 +80,7 @@ func TestEmailNotifier(t *testing.T) {
 			"subject":      "[FIRING:1]  (AlwaysFiring warning)",
 			"to":           []string{"someops@example.com", "somedev@example.com"},
 			"single_email": false,
-			"template":     "ng_alert_notification.html",
+			"template":     "ng_alert_notification",
 			"data": map[string]interface{}{
 				"Title":   "[FIRING:1]  (AlwaysFiring warning)",
 				"Message": "[FIRING:1]  (AlwaysFiring warning)",

pkg/services/notifications/email.go

@@ -17,7 +17,7 @@ type Message struct {
 	SingleEmail   bool
 	From          string
 	Subject       string
-	Body          string
+	Body          map[string]string
 	Info          string
 	ReplyTo       []string
 	EmbeddedFiles []string

pkg/services/notifications/mailer.go

@@ -67,18 +67,7 @@ func (ns *NotificationService) dialAndSend(messages ...*Message) (int, error) {
 	}
 
 	for _, msg := range messages {
-		m := gomail.NewMessage()
-		m.SetHeader("From", msg.From)
-		m.SetHeader("To", msg.To...)
-		m.SetHeader("Subject", msg.Subject)
-
-		ns.setFiles(m, msg)
-
-		for _, replyTo := range msg.ReplyTo {
-			m.SetAddressHeader("Reply-To", replyTo, "")
-		}
-
-		m.SetBody("text/html", msg.Body)
+		m := ns.buildEmail(msg)
 
 		innerError := dialer.DialAndSend(m)
 		emailsSentTotal.Inc()
@@ -100,6 +89,28 @@ func (ns *NotificationService) dialAndSend(messages ...*Message) (int, error) {
 	return sentEmailsCount, err
 }
 
+func (ns *NotificationService) buildEmail(msg *Message) *gomail.Message {
+	m := gomail.NewMessage()
+	m.SetHeader("From", msg.From)
+	m.SetHeader("To", msg.To...)
+	m.SetHeader("Subject", msg.Subject)
+	ns.setFiles(m, msg)
+	for _, replyTo := range msg.ReplyTo {
+		m.SetAddressHeader("Reply-To", replyTo, "")
+	}
+	// loop over content types from settings in reverse order as they are ordered in according to descending
+	// preference while the alternatives should be ordered according to ascending preference
+	for i := len(ns.Cfg.Smtp.ContentTypes) - 1; i >= 0; i-- {
+		if i == len(ns.Cfg.Smtp.ContentTypes)-1 {
+			m.SetBody(ns.Cfg.Smtp.ContentTypes[i], msg.Body[ns.Cfg.Smtp.ContentTypes[i]])
+		} else {
+			m.AddAlternative(ns.Cfg.Smtp.ContentTypes[i], msg.Body[ns.Cfg.Smtp.ContentTypes[i]])
+		}
+	}
+
+	return m
+}
+
 // setFiles attaches files in various forms
 func (ns *NotificationService) setFiles(
 	m *gomail.Message,
@@ -169,18 +180,26 @@ func (ns *NotificationService) buildEmailMessage(cmd *models.SendEmailCommand) (
 		return nil, models.ErrSmtpNotEnabled
 	}
 
-	var buffer bytes.Buffer
-	var err error
-
 	data := cmd.Data
 	if data == nil {
 		data = make(map[string]interface{}, 10)
 	}
 
 	setDefaultTemplateData(data, nil)
-	err = mailTemplates.ExecuteTemplate(&buffer, cmd.Template, data)
-	if err != nil {
-		return nil, err
+
+	body := make(map[string]string)
+	for _, contentType := range ns.Cfg.Smtp.ContentTypes {
+		fileExtension, err := getFileExtensionByContentType(contentType)
+		if err != nil {
+			return nil, err
+		}
+		var buffer bytes.Buffer
+		err = mailTemplates.ExecuteTemplate(&buffer, cmd.Template+fileExtension, data)
+		if err != nil {
+			return nil, err
+		}
+
+		body[contentType] = buffer.String()
 	}
 
 	subject := cmd.Subject
@@ -213,7 +232,7 @@ func (ns *NotificationService) buildEmailMessage(cmd *models.SendEmailCommand) (
 		SingleEmail:   cmd.SingleEmail,
 		From:          addr.String(),
 		Subject:       subject,
-		Body:          buffer.String(),
+		Body:          body,
 		EmbeddedFiles: cmd.EmbeddedFiles,
 		AttachedFiles: buildAttachedFiles(cmd.AttachedFiles),
 		ReplyTo:       cmd.ReplyTo,
@@ -235,3 +254,14 @@ func buildAttachedFiles(
 
 	return result
 }
+
+func getFileExtensionByContentType(contentType string) (string, error) {
+	switch contentType {
+	case "text/html":
+		return ".html", nil
+	case "text/plain":
+		return ".txt", nil
+	default:
+		return "", fmt.Errorf("unrecognized content type %q", contentType)
+	}
+}

pkg/services/notifications/mailer_test.go

@@ -0,0 +1,41 @@
+package notifications
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/grafana/grafana/pkg/setting"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBuildMail(t *testing.T) {
+	ns := &NotificationService{
+		Cfg: setting.NewCfg(),
+	}
+	ns.Cfg.Smtp.ContentTypes = []string{"text/html", "text/plain"}
+
+	message := &Message{
+		To:      []string{"to@address.com"},
+		From:    "from@address.com",
+		Subject: "Some subject",
+		Body: map[string]string{
+			"text/html":  "Some HTML body",
+			"text/plain": "Some plain text body",
+		},
+		ReplyTo: []string{"from@address.com"},
+	}
+
+	t.Run("When building email", func(t *testing.T) {
+		email := ns.buildEmail(message)
+
+		buf := new(bytes.Buffer)
+		_, err := email.WriteTo(buf)
+		require.NoError(t, err)
+
+		assert.Contains(t, buf.String(), "Some HTML body")
+		assert.Contains(t, buf.String(), "Some plain text body")
+		assert.Less(t, strings.Index(buf.String(), "Some plain text body"), strings.Index(buf.String(), "Some HTML body"))
+	})
+}

pkg/services/notifications/notifications.go

@@ -19,9 +19,9 @@ import (
 )
 
 var mailTemplates *template.Template
-var tmplResetPassword = "reset_password.html"
-var tmplSignUpStarted = "signup_started.html"
-var tmplWelcomeOnSignUp = "welcome_on_signup.html"
+var tmplResetPassword = "reset_password"
+var tmplSignUpStarted = "signup_started"
+var tmplWelcomeOnSignUp = "welcome_on_signup"
 
 func init() {
 	registry.RegisterService(&NotificationService{})
@@ -56,10 +56,12 @@ func (ns *NotificationService) Init() error {
 		"Subject": subjectTemplateFunc,
 	})
 
-	templatePattern := filepath.Join(ns.Cfg.StaticRootPath, ns.Cfg.Smtp.TemplatesPattern)
-	_, err := mailTemplates.ParseGlob(templatePattern)
-	if err != nil {
-		return err
+	for _, pattern := range ns.Cfg.Smtp.TemplatesPatterns {
+		templatePattern := filepath.Join(ns.Cfg.StaticRootPath, pattern)
+		_, err := mailTemplates.ParseGlob(templatePattern)
+		if err != nil {
+			return err
+		}
 	}
 
 	if !util.IsEmail(ns.Cfg.Smtp.FromAddress) {

pkg/services/notifications/notifications_test.go

@@ -16,9 +16,10 @@ func TestNotificationService(t *testing.T) {
 	}
 	ns.Cfg.StaticRootPath = "../../../public/"
 	ns.Cfg.Smtp.Enabled = true
-	ns.Cfg.Smtp.TemplatesPattern = "emails/*.html"
+	ns.Cfg.Smtp.TemplatesPatterns = []string{"emails/*.html", "emails/*.txt"}
 	ns.Cfg.Smtp.FromAddress = "from@address.com"
 	ns.Cfg.Smtp.FromName = "Grafana Admin"
+	ns.Cfg.Smtp.ContentTypes = []string{"text/html", "text/plain"}
 	ns.Bus = bus.New()
 
 	err := ns.Init()
@@ -29,8 +30,10 @@ func TestNotificationService(t *testing.T) {
 		require.NoError(t, err)
 
 		sentMsg := <-ns.mailQueue
-		assert.Contains(t, sentMsg.Body, "body")
+		assert.Contains(t, sentMsg.Body["text/html"], "body")
+		assert.NotContains(t, sentMsg.Body["text/plain"], "body")
 		assert.Equal(t, "Reset your Grafana password - asd@asd.com", sentMsg.Subject)
-		assert.NotContains(t, sentMsg.Body, "Subject")
+		assert.NotContains(t, sentMsg.Body["text/html"], "Subject")
+		assert.NotContains(t, sentMsg.Body["text/plain"], "Subject")
 	})
 }

pkg/services/notifications/send_email_integration_test.go

@@ -19,9 +19,10 @@ func TestEmailIntegrationTest(t *testing.T) {
 		ns.Bus = bus.New()
 		ns.Cfg = setting.NewCfg()
 		ns.Cfg.Smtp.Enabled = true
-		ns.Cfg.Smtp.TemplatesPattern = "emails/*.html"
+		ns.Cfg.Smtp.TemplatesPatterns = []string{"emails/*.html", "emails/*.txt"}
 		ns.Cfg.Smtp.FromAddress = "from@address.com"
 		ns.Cfg.Smtp.FromName = "Grafana Admin"
+		ns.Cfg.Smtp.ContentTypes = []string{"text/html", "text/plain"}
 
 		err := ns.Init()
 		So(err, ShouldBeNil)
@@ -52,7 +53,7 @@ func TestEmailIntegrationTest(t *testing.T) {
 					},
 				},
 				To:       []string{"asdf@asdf.com"},
-				Template: "alert_notification.html",
+				Template: "alert_notification",
 			}
 
 			err := ns.sendEmailCommandHandler(cmd)
@@ -61,7 +62,9 @@ func TestEmailIntegrationTest(t *testing.T) {
 			sentMsg := <-ns.mailQueue
 			So(sentMsg.From, ShouldEqual, "Grafana Admin <from@address.com>")
 			So(sentMsg.To[0], ShouldEqual, "asdf@asdf.com")
-			err = ioutil.WriteFile("../../../tmp/test_email.html", []byte(sentMsg.Body), 0777)
+			err = ioutil.WriteFile("../../../tmp/test_email.html", []byte(sentMsg.Body["text/html"]), 0777)
+			So(err, ShouldBeNil)
+			err = ioutil.WriteFile("../../../tmp/test_email.txt", []byte(sentMsg.Body["text/plain"]), 0777)
 			So(err, ShouldBeNil)
 		})
 	})

pkg/setting/setting_smtp.go

@@ -1,5 +1,7 @@
 package setting
 
+import "github.com/grafana/grafana/pkg/util"
+
 type SmtpSettings struct {
 	Enabled        bool
 	Host           string
@@ -14,7 +16,8 @@ type SmtpSettings struct {
 	SkipVerify     bool
 
 	SendWelcomeEmailOnSignUp bool
-	TemplatesPattern         string
+	TemplatesPatterns        []string
+	ContentTypes             []string
 }
 
 func (cfg *Cfg) readSmtpSettings() {
@@ -33,5 +36,6 @@ func (cfg *Cfg) readSmtpSettings() {
 
 	emails := cfg.Raw.Section("emails")
 	cfg.Smtp.SendWelcomeEmailOnSignUp = emails.Key("welcome_email_on_sign_up").MustBool(false)
-	cfg.Smtp.TemplatesPattern = emails.Key("templates_pattern").MustString("emails/*.html")
+	cfg.Smtp.TemplatesPatterns = util.SplitString(emails.Key("templates_pattern").MustString("emails/*.html, emails/*.txt"))
+	cfg.Smtp.ContentTypes = util.SplitString(emails.Key("content_types").MustString("text/html"))
 }

pkg/tests/api/alerting/api_notification_channel_test.go

@@ -1369,7 +1369,7 @@ var expEmailNotifications = []*models.SendEmailCommandSync{
 		SendEmailCommand: models.SendEmailCommand{
 			To:          []string{"test@email.com"},
 			SingleEmail: true,
-			Template:    "ng_alert_notification.html",
+			Template:    "ng_alert_notification",
 			Subject:     "[FIRING:1] EmailAlert ",
 			Data: map[string]interface{}{
 				"Title":   "[FIRING:1] EmailAlert ",