Alerting: Add image url or file attachment to email notifications. (#49381)

If an image token is present in an alert instance, the email notifier will attempt to find a public URL for the image token. If found, it will add that to the email as the `ImageLink` field. If only local file data is available, the notifier will attach the file to the outgoing email using the `EmbeddedImage` field.

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

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"net/url"
+	"os"
 	"path"
 
 	"github.com/prometheus/alertmanager/template"
@@ -24,6 +25,7 @@ type EmailNotifier struct {
 	Message     string
 	log         log.Logger
 	ns          notifications.EmailSender
+	images      ImageStore
 	tmpl        *template.Template
 }
 
@@ -42,7 +44,7 @@ func EmailFactory(fc FactoryConfig) (NotificationChannel, error) {
 			Cfg:    *fc.Config,
 		}
 	}
-	return NewEmailNotifier(cfg, fc.NotificationService, fc.Template), nil
+	return NewEmailNotifier(cfg, fc.NotificationService, fc.ImageStore, fc.Template), nil
 }
 
 func NewEmailConfig(config *NotificationChannelConfig) (*EmailConfig, error) {
@@ -62,7 +64,7 @@ func NewEmailConfig(config *NotificationChannelConfig) (*EmailConfig, error) {
 
 // NewEmailNotifier is the constructor function
 // for the EmailNotifier.
-func NewEmailNotifier(config *EmailConfig, ns notifications.EmailSender, t *template.Template) *EmailNotifier {
+func NewEmailNotifier(config *EmailConfig, ns notifications.EmailSender, images ImageStore, t *template.Template) *EmailNotifier {
 	return &EmailNotifier{
 		Base: NewBase(&models.AlertNotification{
 			Uid:                   config.UID,
@@ -76,6 +78,7 @@ func NewEmailNotifier(config *EmailConfig, ns notifications.EmailSender, t *temp
 		Message:     config.Message,
 		log:         log.New("alerting.notifier.email"),
 		ns:          ns,
+		images:      images,
 		tmpl:        t,
 	}
 }
@@ -121,6 +124,41 @@ func (en *EmailNotifier) Notify(ctx context.Context, as ...*types.Alert) (bool,
 		},
 	}
 
+	// TODO: modify the email sender code to support multiple file or image URL
+	// fields. We cannot use images from every alert yet.
+	imgToken := getTokenFromAnnotations(as[0].Annotations)
+	if len(imgToken) != 0 {
+		timeoutCtx, cancel := context.WithTimeout(ctx, ImageStoreTimeout)
+		imgURL, err := en.images.GetURL(timeoutCtx, imgToken)
+		cancel()
+		if err != nil {
+			if !errors.Is(err, ErrImagesUnavailable) {
+				// Ignore errors. Don't log "ImageUnavailable", which means the storage doesn't exist.
+				en.log.Warn("failed to retrieve image url from store", "error", err)
+			}
+		} else if len(imgURL) > 0 {
+			cmd.Data["ImageLink"] = imgURL
+		} else { // Try to upload
+			timeoutCtx, cancel := context.WithTimeout(ctx, ImageStoreTimeout)
+			imgPath, err := en.images.GetFilepath(timeoutCtx, imgToken)
+			cancel()
+			if err != nil {
+				if !errors.Is(err, ErrImagesUnavailable) {
+					// Ignore errors. Don't log "ImageUnavailable", which means the storage doesn't exist.
+					en.log.Warn("failed to retrieve image url from store", "error", err)
+				}
+			} else if len(imgPath) != 0 {
+				file, err := os.Stat(imgPath)
+				if err == nil {
+					cmd.EmbeddedFiles = []string{imgPath}
+					cmd.Data["EmbeddedImage"] = file.Name()
+				} else {
+					en.log.Warn("failed to access email notification image attachment data", "error", err)
+				}
+			}
+		}
+	}
+
 	if tmplErr != nil {
 		en.log.Warn("failed to template email message", "err", tmplErr.Error())
 	}

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

@@ -52,7 +52,7 @@ func TestEmailNotifier(t *testing.T) {
 			Settings: settingsJSON,
 		})
 		require.NoError(t, err)
-		emailNotifier := NewEmailNotifier(cfg, emailSender, tmpl)
+		emailNotifier := NewEmailNotifier(cfg, emailSender, &UnavailableImageStore{}, tmpl)
 
 		alerts := []*types.Alert{
 			{
@@ -289,7 +289,7 @@ func createSut(t *testing.T, messageTmpl string, emailTmpl *template.Template, n
 		Settings: settingsJSON,
 	})
 	require.NoError(t, err)
-	emailNotifier := NewEmailNotifier(cfg, ns, emailTmpl)
+	emailNotifier := NewEmailNotifier(cfg, ns, &UnavailableImageStore{}, emailTmpl)
 
 	return emailNotifier
 }

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

@@ -22,6 +22,7 @@ type FactoryConfig struct {
 // A specialization of store.ImageStore, to avoid an import loop.
 type ImageStore interface {
 	GetURL(ctx context.Context, token string) (string, error)
+	GetFilepath(ctx context.Context, token string) (string, error)
 	GetData(ctx context.Context, token string) (io.ReadCloser, error)
 }
 

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

@@ -51,6 +51,10 @@ func (n *UnavailableImageStore) GetURL(ctx context.Context, token string) (strin
 	return "", ErrImagesUnavailable
 }
 
+func (n *UnavailableImageStore) GetFilepath(ctx context.Context, token string) (string, error) {
+	return "", ErrImagesUnavailable
+}
+
 func (n *UnavailableImageStore) GetData(ctx context.Context, token string) (io.ReadCloser, error) {
 	return nil, ErrImagesUnavailable
 }

pkg/services/ngalert/notifier/testing.go

@@ -23,6 +23,10 @@ func (f *FakeConfigStore) GetURL(ctx context.Context, token string) (string, err
 	return "", store.ErrImageNotFound
 }
 
+func (f *FakeConfigStore) GetFilepath(ctx context.Context, token string) (string, error) {
+	return "", store.ErrImageNotFound
+}
+
 // Returns an io.ReadCloser that reads out the image data for the provided
 // token, if available. May return ErrImageNotFound.
 func (f *FakeConfigStore) GetData(ctx context.Context, token string) (io.ReadCloser, error) {

pkg/services/ngalert/store/image.go

@@ -41,6 +41,8 @@ type ImageStore interface {
 
 	GetURL(ctx context.Context, token string) (string, error)
 
+	GetFilepath(ctx context.Context, token string) (string, error)
+
 	// Returns an io.ReadCloser that reads out the image data for the provided
 	// token, if available. May return ErrImageNotFound.
 	GetData(ctx context.Context, token string) (io.ReadCloser, error)
@@ -99,6 +101,14 @@ func (st *DBstore) GetURL(ctx context.Context, token string) (string, error) {
 	return img.URL, nil
 }
 
+func (st *DBstore) GetFilepath(ctx context.Context, token string) (string, error) {
+	img, err := st.GetImage(ctx, token)
+	if err != nil {
+		return "", err
+	}
+	return img.Path, nil
+}
+
 func (st *DBstore) GetData(ctx context.Context, token string) (io.ReadCloser, error) {
 	// TODO: Should we support getting data from image.URL? One could configure
 	// the system to upload to S3 while still reading data for notifiers like