Alerting: Fix image embed in email template. (#50370)

The ng_alert_notification email template did not include templating for
linked or embedded images. This change updates that.

Additionally, this change supports embedding an image for each alert in
an email batch.

Fixes #50315

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

@@ -89,12 +89,11 @@ func NewEmailNotifier(config *EmailConfig, ns notifications.EmailSender, images
 }
 
 // Notify sends the alert notification.
-func (en *EmailNotifier) Notify(ctx context.Context, as ...*types.Alert) (bool, error) {
+func (en *EmailNotifier) Notify(ctx context.Context, alerts ...*types.Alert) (bool, error) {
 	var tmplErr error
-	tmpl, data := TmplText(ctx, en.tmpl, as, en.log, &tmplErr)
+	tmpl, data := TmplText(ctx, en.tmpl, alerts, en.log, &tmplErr)
 
 	subject := tmpl(en.Subject)
-
 	alertPageURL := en.tmpl.ExternalURL.String()
 	ruleURL := en.tmpl.ExternalURL.String()
 	u, err := url.Parse(en.tmpl.ExternalURL.String())
@@ -108,6 +107,26 @@ func (en *EmailNotifier) Notify(ctx context.Context, as ...*types.Alert) (bool,
 		en.log.Debug("failed to parse external URL", "url", en.tmpl.ExternalURL.String(), "err", err.Error())
 	}
 
+	// Extend alerts data with images, if available.
+	var embeddedFiles []string
+	_ = withStoredImages(ctx, en.log, en.images,
+		func(index int, image *ngmodels.Image) error {
+			if image != nil {
+				if len(image.URL) != 0 {
+					data.Alerts[index].ImageURL = image.URL
+				} else if len(image.Path) != 0 {
+					_, err := os.Stat(image.Path)
+					if err == nil {
+						data.Alerts[index].EmbeddedImage = path.Base(image.Path)
+						embeddedFiles = append(embeddedFiles, image.Path)
+					} else {
+						en.log.Warn("failed to get image file for email attachment", "file", image.Path, "err", err)
+					}
+				}
+			}
+			return nil
+		}, alerts...)
+
 	cmd := &models.SendEmailCommandSync{
 		SendEmailCommand: models.SendEmailCommand{
 			Subject: subject,
@@ -123,34 +142,13 @@ func (en *EmailNotifier) Notify(ctx context.Context, as ...*types.Alert) (bool,
 				"RuleUrl":           ruleURL,
 				"AlertPageUrl":      alertPageURL,
 			},
+			EmbeddedFiles: embeddedFiles,
 			To:            en.Addresses,
 			SingleEmail:   en.SingleEmail,
 			Template:      "ng_alert_notification",
 		},
 	}
 
-	// TODO: modify the email sender code to support multiple file or image URL
-	// fields. We cannot use images from every alert yet.
-	_ = withStoredImage(ctx, en.log, en.images,
-		func(index int, image *ngmodels.Image) error {
-			if image == nil {
-				return nil
-			}
-
-			if len(image.URL) != 0 {
-				cmd.Data["ImageLink"] = image.URL
-			} else if len(image.Path) != 0 {
-				file, err := os.Stat(image.Path)
-				if err == nil {
-					cmd.EmbeddedFiles = []string{image.Path}
-					cmd.Data["EmbeddedImage"] = file.Name()
-				} else {
-					en.log.Warn("failed to access email notification image attachment data", "err", err)
-				}
-			}
-			return nil
-		}, 0, as...)
-
 	if tmplErr != nil {
 		en.log.Warn("failed to template email message", "err", tmplErr.Error())
 	}

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

@@ -30,6 +30,7 @@ type ExtendedAlert struct {
 	PanelURL      string      `json:"panelURL"`
 	ValueString   string      `json:"valueString"`
 	ImageURL      string      `json:"imageURL,omitempty"`
+	EmbeddedImage string      `json:"embeddedImage,omitempty"`
 }
 
 type ExtendedAlerts []ExtendedAlert

public/emails/ng_alert_notification.html

@@ -210,6 +210,21 @@ text-decoration: underline;
 {{Subject .Subject "{{.Title}}"}}
 
 {{ define "alert" }}
+
+  {{if ne .ImageURL "" }}
+  <tr style="vertical-align: top; padding: 0;" align="left">
+    <td colspan="2" style="word-break: break-word; -webkit-hyphens: auto; -moz-hyphens: auto; hyphens: auto; border-collapse: collapse !important; color: #222222; font-family: 'Open Sans', 'Helvetica Neue', 'Helvetica', Helvetica, Arial, sans-serif; font-weight: normal; line-height: 19px; font-size: 14px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none; margin: 0; padding: 24px 0 0;" align="left" valign="top">
+       <img src="{{.ImageURL}}" class="fluid-centered" alt="Alerting Panel" style="outline: none !important; text-decoration: none !important; -ms-interpolation-mode: bicubic; width: auto; clear: both; display: block; border: 0;" align="left" />
+		</td>
+	</tr>
+  {{end}}
+  {{if ne .EmbeddedImage "" }}
+  <tr style="vertical-align: top; padding: 0;" align="left">
+    <td colspan="2" style="word-break: break-word; -webkit-hyphens: auto; -moz-hyphens: auto; hyphens: auto; border-collapse: collapse !important; color: #222222; font-family: 'Open Sans', 'Helvetica Neue', 'Helvetica', Helvetica, Arial, sans-serif; font-weight: normal; line-height: 19px; font-size: 14px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none; margin: 0; padding: 24px 0 0;" align="left" valign="top">
+       <img src="cid:{{.EmbeddedImage}}" alt="Alerting Chart Attached Below" style="outline: none !important; text-decoration: none !important; -ms-interpolation-mode: bicubic; width: auto; clear: both; display: block; border: 0;" align="left" />
+		</td>
+	</tr>
+	{{end}}
   <tr style="vertical-align: top; padding: 0;" align="left">
     <td colspan="2" class="value" style="word-break: break-word; -webkit-hyphens: auto; -moz-hyphens: auto; hyphens: auto; border-collapse: collapse !important; color: #222222; font-family: 'Open Sans', 'Helvetica Neue', 'Helvetica', Helvetica, Arial, sans-serif; font-weight: normal; line-height: 19px; font-size: 14px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none; margin: 0; padding: 24px 0 0;" align="left" valign="top">
       <span class="value-heading" style="font-weight: bold;">Value:</span> <span class="value-value" style="padding-left: 8px;">{{ .ValueString }}</span>