Alerting: Adds support for sending a single email to all recipients in notification channel (#21091)

When an alert is sent by e-mail, the process sends an e-mail to 
each recipient separately. This PR is a single delivery to all recipients.
For companies that use e-mail extensively, this is necessary in order 
not to overload the sending queue.

Replaces #18013
Fixes #12650

Co-authored-by: Henrique Oliveira <holiiveira@users.noreply.github.com>

pkg/models/notifications.go

@@ -14,6 +14,7 @@ type SendEmailAttachFile struct {
 // SendEmailCommand is command for sending emails
 type SendEmailCommand struct {
 	To            []string
+	SingleEmail   bool
 	Template      string
 	Subject       string
 	Data          map[string]interface{}

pkg/services/alerting/notifiers/email.go

@@ -19,13 +19,25 @@ func init() {
 		Description: "Sends notifications using Grafana server configured SMTP settings",
 		Factory:     NewEmailNotifier,
 		OptionsTemplate: `
-      <h3 class="page-heading">Email addresses</h3>
-      <div class="gf-form">
-         <textarea rows="7" class="gf-form-input width-27" required ng-model="ctrl.model.settings.addresses"></textarea>
-      </div>
-      <div class="gf-form">
-      <span>You can enter multiple email addresses using a ";" separator</span>
-      </div>
+			<h3 class="page-heading">Email settings</h3>
+			<div class="gf-form">
+				<gf-form-switch
+					class="gf-form"
+					label="Single email"
+					label-class="width-8"
+					checked="ctrl.model.settings.singleEmail"
+					tooltip="Send a single email to all recipients">
+				</gf-form-switch>
+			</div>
+			<div class="gf-form">
+				<label class="gf-form-label width-8">
+					Addresses
+				</label>
+				<textarea rows="7" class="gf-form-input width-27" required ng-model="ctrl.model.settings.addresses"></textarea>
+			</div>
+			<div class="gf-form offset-width-8">
+				<span>You can enter multiple email addresses using a ";" separator</span>
+			</div>
     `,
 	})
 }
@@ -34,14 +46,16 @@ func init() {
 // alert notifications over email.
 type EmailNotifier struct {
 	NotifierBase
-	Addresses []string
-	log       log.Logger
+	Addresses   []string
+	SingleEmail bool
+	log         log.Logger
 }
 
 // NewEmailNotifier is the constructor function
 // for the EmailNotifier.
 func NewEmailNotifier(model *models.AlertNotification) (alerting.Notifier, 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"}
@@ -53,13 +67,14 @@ func NewEmailNotifier(model *models.AlertNotification) (alerting.Notifier, error
 	return &EmailNotifier{
 		NotifierBase: NewNotifierBase(model),
 		Addresses:    addresses,
+		SingleEmail:  singleEmail,
 		log:          log.New("alerting.notifier.email"),
 	}, nil
 }
 
 // Notify sends the alert notification.
 func (en *EmailNotifier) Notify(evalContext *alerting.EvalContext) error {
-	en.log.Info("Sending alert notification to", "addresses", en.Addresses)
+	en.log.Info("Sending alert notification to", "addresses", en.Addresses, "singleEmail", en.SingleEmail)
 
 	ruleURL, err := evalContext.GetRuleURL()
 	if err != nil {
@@ -89,6 +104,7 @@ func (en *EmailNotifier) Notify(evalContext *alerting.EvalContext) error {
 				"EvalMatches":   evalContext.EvalMatches,
 			},
 			To:           en.Addresses,
+			SingleEmail:  en.SingleEmail,
 			Template:     "alert_notification.html",
 			EmbededFiles: []string{},
 		},

pkg/services/notifications/email.go

@@ -14,6 +14,7 @@ type AttachedFile struct {
 // Message is representation of the email message
 type Message struct {
 	To            []string
+	SingleEmail   bool
 	From          string
 	Subject       string
 	Body          string

pkg/services/notifications/mailer.go

@@ -12,6 +12,7 @@ import (
 	"io"
 	"net"
 	"strconv"
+	"strings"
 
 	gomail "gopkg.in/mail.v2"
 
@@ -21,16 +22,31 @@ import (
 )
 
 func (ns *NotificationService) send(msg *Message) (int, error) {
+	messages := []*Message{}
+
+	if msg.SingleEmail {
+		messages = append(messages, msg)
+	} else {
+		for _, address := range msg.To {
+			copy := *msg
+			copy.To = []string{address}
+			messages = append(messages, &copy)
+		}
+	}
+
+	return ns.dialAndSend(messages...)
+}
+
+func (ns *NotificationService) dialAndSend(messages ...*Message) (num int, err error) {
 	dialer, err := ns.createDialer()
 	if err != nil {
-		return 0, err
+		return
 	}
 
-	var num int
-	for _, address := range msg.To {
+	for _, msg := range messages {
 		m := gomail.NewMessage()
 		m.SetHeader("From", msg.From)
-		m.SetHeader("To", address)
+		m.SetHeader("To", msg.To...)
 		m.SetHeader("Subject", msg.Subject)
 
 		ns.setFiles(m, msg)
@@ -41,16 +57,15 @@ func (ns *NotificationService) send(msg *Message) (int, error) {
 
 		m.SetBody("text/html", msg.Body)
 
-		e := dialer.DialAndSend(m)
-		if e != nil {
-			err = errutil.Wrapf(e, "Failed to send notification to email address: %s", address)
+		if e := dialer.DialAndSend(m); e != nil {
+			err = errutil.Wrapf(e, "Failed to send notification to email addresses: %s", strings.Join(msg.To, ";"))
 			continue
 		}
 
 		num++
 	}
 
-	return num, err
+	return
 }
 
 // setFiles attaches files in various forms
@@ -150,6 +165,7 @@ func (ns *NotificationService) buildEmailMessage(cmd *models.SendEmailCommand) (
 
 	return &Message{
 		To:            cmd.To,
+		SingleEmail:   cmd.SingleEmail,
 		From:          fmt.Sprintf("%s <%s>", ns.Cfg.Smtp.FromName, ns.Cfg.Smtp.FromAddress),
 		Subject:       subject,
 		Body:          buffer.String(),

pkg/services/notifications/notifications.go

@@ -123,6 +123,7 @@ func (ns *NotificationService) sendEmailCommandHandlerSync(ctx context.Context,
 		Info:         cmd.Info,
 		Template:     cmd.Template,
 		To:           cmd.To,
+		SingleEmail:  cmd.SingleEmail,
 		EmbededFiles: cmd.EmbededFiles,
 		Subject:      cmd.Subject,
 	})