Add Delete method

Fixes #611.

Signed-off-by: beorn7 <beorn@grafana.com>

prometheus/push/push.go

@@ -204,6 +204,42 @@ func (p *Pusher) Format(format expfmt.Format) *Pusher {
 	return p
 }
 
+// Delete sends a “DELETE” request to the Pushgateway configured while creating
+// this Pusher, using the configured job name and any added grouping labels as
+// grouping key. Any added Gatherers and Collectors added to this Pusher are
+// ignored by this method.
+//
+// Delete returns the first error encountered by any method call (including this
+// one) in the lifetime of the Pusher.
+func (p *Pusher) Delete() error {
+	if p.error != nil {
+		return p.error
+	}
+	urlComponents := []string{url.QueryEscape(p.job)}
+	for ln, lv := range p.grouping {
+		urlComponents = append(urlComponents, ln, lv)
+	}
+	deleteURL := fmt.Sprintf("%s/metrics/job/%s", p.url, strings.Join(urlComponents, "/"))
+
+	req, err := http.NewRequest(http.MethodDelete, deleteURL, nil)
+	if err != nil {
+		return err
+	}
+	if p.useBasicAuth {
+		req.SetBasicAuth(p.username, p.password)
+	}
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 202 {
+		body, _ := ioutil.ReadAll(resp.Body) // Ignore any further error as this is for an error message only.
+		return fmt.Errorf("unexpected status code %d while deleting %s: %s", resp.StatusCode, deleteURL, body)
+	}
+	return nil
+}
+
 func (p *Pusher) push(method string) error {
 	if p.error != nil {
 		return p.error

prometheus/push/push_test.go

@@ -191,4 +191,22 @@ func TestPush(t *testing.T) {
 	if lastPath != "/metrics/job/testjob/a/x/b/y" && lastPath != "/metrics/job/testjob/b/y/a/x" {
 		t.Error("unexpected path:", lastPath)
 	}
+
+	// Delete, all good.
+	if err := New(pgwOK.URL, "testjob").
+		Grouping("a", "x").
+		Grouping("b", "y").
+		Delete(); err != nil {
+		t.Fatal(err)
+	}
+	if lastMethod != "DELETE" {
+		t.Error("want method DELETE for delete, got", lastMethod)
+	}
+	if len(lastBody) != 0 {
+		t.Errorf("got body of length %d, want empty body", len(lastBody))
+	}
+	if lastPath != "/metrics/job/testjob/a/x/b/y" && lastPath != "/metrics/job/testjob/b/y/a/x" {
+		t.Error("unexpected path:", lastPath)
+	}
+
 }