adding support for token-based slack file.upload API call for posting images to slack

docs/sources/alerting/notifications.md

@@ -48,12 +48,15 @@ external image destination if available or fallback to attaching the image in th
 
 To set up slack you need to configure an incoming webhook url at slack. You can follow their guide for how
 to do that https://api.slack.com/incoming-webhooks If you want to include screenshots of the firing alerts
-in the slack messages you have to configure the [external image destination](#external-image-store) in Grafana.
+in the slack messages you have to configure either the [external image destination](#external-image-store) in Grafana,
+or a bot integration via Slack Apps. Follow Slack's guide to set up a bot integration and use the token provided
+https://api.slack.com/bot-users, which starts with "xoxb".
 
 Setting | Description
 ---------- | -----------
 Recipient | allows you to override the slack recipient.
 Mention | make it possible to include a mention in the slack notification sent by Grafana. Ex @here or @channel
+Token | If provided, Grafana will upload the generated image via Slack's file.upload API method, not the external image destination.
 
 ### PagerDuty
 

pkg/services/alerting/notifiers/slack.go

 package notifiers
 
 import (
+	"bytes"
 	"encoding/json"
+	"io"
+	"mime/multipart"
+	"os"
 	"time"
 
 	"github.com/grafana/grafana/pkg/bus"
@@ -15,7 +19,7 @@ func init() {
 	alerting.RegisterNotifier(&alerting.NotifierPlugin{
 		Type:        "slack",
 		Name:        "Slack",
-		Description: "Sends notifications using Grafana server configured STMP settings",
+		Description: "Sends notifications to Slack via Slack Webhooks",
 		Factory:     NewSlackNotifier,
 		OptionsTemplate: `
       <h3 class="page-heading">Slack settings</h3>
@@ -45,6 +49,17 @@ func init() {
           Mention a user or a group using @ when notifying in a channel
         </info-popover>
       </div>
+      <div class="gf-form max-width-30">
+        <span class="gf-form-label width-6">Token</span>
+        <input type="text"
+          class="gf-form-input max-width-30"
+          ng-model="ctrl.model.settings.token"
+          data-placement="right">
+        </input>
+        <info-popover mode="right-absolute">
+          Provide a bot token to use the Slack file.upload API (starts with "xoxb")
+        </info-popover>
+      </div>
     `,
 	})
 
@@ -58,12 +73,14 @@ func NewSlackNotifier(model *m.AlertNotification) (alerting.Notifier, error) {
 
 	recipient := model.Settings.Get("recipient").MustString()
 	mention := model.Settings.Get("mention").MustString()
+	token := model.Settings.Get("token").MustString()
 
 	return &SlackNotifier{
 		NotifierBase: NewNotifierBase(model.Id, model.IsDefault, model.Name, model.Type, model.Settings),
 		Url:          url,
 		Recipient:    recipient,
 		Mention:      mention,
+		Token:        token,
 		log:          log.New("alerting.notifier.slack"),
 	}, nil
 }
@@ -73,6 +90,7 @@ type SlackNotifier struct {
 	Url       string
 	Recipient string
 	Mention   string
+	Token     string
 	log       log.Logger
 }
 
@@ -110,6 +128,11 @@ func (this *SlackNotifier) Notify(evalContext *alerting.EvalContext) error {
 	if evalContext.Rule.State != m.AlertStateOK { //dont add message when going back to alert state ok.
 		message += " " + evalContext.Rule.Message
 	}
+	image_url := ""
+	// default to file.upload API method if a token is provided
+	if this.Token == "" {
+		image_url = evalContext.ImagePublicUrl
+	}
 
 	body := map[string]interface{}{
 		"attachments": []map[string]interface{}{
@@ -120,7 +143,7 @@ func (this *SlackNotifier) Notify(evalContext *alerting.EvalContext) error {
 				"title_link":  ruleUrl,
 				"text":        message,
 				"fields":      fields,
-				"image_url":   evalContext.ImagePublicUrl,
+				"image_url":   image_url,
 				"footer":      "Grafana v" + setting.BuildVersion,
 				"footer_icon": "https://grafana.com/assets/img/fav32.png",
 				"ts":          time.Now().Unix(),
@@ -133,14 +156,69 @@ func (this *SlackNotifier) Notify(evalContext *alerting.EvalContext) error {
 	if this.Recipient != "" {
 		body["channel"] = this.Recipient
 	}
-
 	data, _ := json.Marshal(&body)
 	cmd := &m.SendWebhookSync{Url: this.Url, Body: string(data)}
-
 	if err := bus.DispatchCtx(evalContext.Ctx, cmd); err != nil {
 		this.log.Error("Failed to send slack notification", "error", err, "webhook", this.Name)
 		return err
 	}
+	if this.Token != "" {
+		slackUploadUrl := "https://slack.com/api/files.upload"
+		if evalContext.ImageOnDiskPath == "" {
+			evalContext.ImageOnDiskPath = "public/img/mixed_styles.png"
+		}
+		this.log.Info("Uploading to slack via file.upload API")
+		headers, uploadBody, err := GenerateSlackUpload(evalContext.ImageOnDiskPath, this.Token, this.Recipient)
+		if err != nil {
+			return err
+		}
+		cmd := &m.SendWebhookSync{Url: slackUploadUrl, Body: uploadBody.String(), HttpHeader: headers, HttpMethod: "POST"}
+		if err := bus.DispatchCtx(evalContext.Ctx, cmd); err != nil {
+			this.log.Error("Failed to upload slack image", "error", err, "webhook", "file.upload")
+			return err
+		}
+		if err != nil {
+			return err
+		}
+	}
 
 	return nil
 }
+
+func GenerateSlackUpload(file string, token string, recipient string) (map[string]string, bytes.Buffer, error) {
+	// Slack requires all POSTs to files.upload to present
+	// an "application/x-www-form-urlencoded" encoded querystring
+	// See https://api.slack.com/methods/files.upload
+	var b bytes.Buffer
+	w := multipart.NewWriter(&b)
+	// Add the generated image file
+	f, err := os.Open(file)
+	if err != nil {
+		return nil, b, err
+	}
+	defer f.Close()
+	fw, err := w.CreateFormFile("file", file)
+	if err != nil {
+		return nil, b, err
+	}
+	_, err = io.Copy(fw, f)
+	if err != nil {
+		return nil, b, err
+	}
+	// Add the authorization token
+	err = w.WriteField("token", token)
+	if err != nil {
+		return nil, b, err
+	}
+	// Add the channel(s) to POST to
+	err = w.WriteField("channels", recipient)
+	if err != nil {
+		return nil, b, err
+	}
+	w.Close()
+	headers := map[string]string{
+		"Content-Type":  w.FormDataContentType(),
+		"Authorization": "auth_token=\"" + token + "\"",
+	}
+	return headers, b, nil
+}

pkg/services/alerting/notifiers/slack_test.go

@@ -48,6 +48,7 @@ func TestSlackNotifier(t *testing.T) {
 				So(slackNotifier.Url, ShouldEqual, "http://google.com")
 				So(slackNotifier.Recipient, ShouldEqual, "")
 				So(slackNotifier.Mention, ShouldEqual, "")
+				So(slackNotifier.Token, ShouldEqual, "")
 			})
 
 			Convey("from settings with Recipient and Mention", func() {
@@ -56,6 +57,7 @@ func TestSlackNotifier(t *testing.T) {
           "url": "http://google.com",
           "recipient": "#ds-opentsdb",
           "mention": "@carl"
+          "token": "xoxb-XXXXXXXX-XXXXXXXX-XXXXXXXXXX",
 				}`
 
 				settingsJSON, _ := simplejson.NewJson([]byte(json))
@@ -74,6 +76,7 @@ func TestSlackNotifier(t *testing.T) {
 				So(slackNotifier.Url, ShouldEqual, "http://google.com")
 				So(slackNotifier.Recipient, ShouldEqual, "#ds-opentsdb")
 				So(slackNotifier.Mention, ShouldEqual, "@carl")
+				So(slackNotifier.Token, ShouldEqual, "xoxb-XXXXXXXX-XXXXXXXX-XXXXXXXXXX")
 			})
 
 		})