fix(api): correctly return metrics, support bundle (fixes #10847) (#10849)

Our faked request wasn't good enough; improve it, adding a test.

Signed-off-by: Jakob Borg <jakob@kastelo.net>

lib/api/api.go

@@ -1184,10 +1184,7 @@ func (s *service) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Metrics data as text
-	var metricsBuf bytes.Buffer
+	files = append(files, fileEntry{name: "metrics.txt", data: prometheusMetrics()})
-	wr := bufferedResponseWriter{Writer: &metricsBuf}
-	promhttp.Handler().ServeHTTP(wr, &http.Request{Method: http.MethodGet})
-	files = append(files, fileEntry{name: "metrics.txt", data: metricsBuf.Bytes()})
 
 	// Connection data as JSON
 	connStats := s.model.ConnectionStats()
@@ -1258,6 +1255,16 @@ func (s *service) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	io.Copy(w, &zipFilesBuffer)
 }
 
+func prometheusMetrics() []byte {
+	var metricsBuf bytes.Buffer
+	wr := bufferedResponseWriter{Writer: &metricsBuf}
+	promhttp.Handler().ServeHTTP(wr, &http.Request{
+		Method: http.MethodGet,
+		URL:    &url.URL{Scheme: "http://", Host: "localhost", Path: "/metrics"},
+	})
+	return metricsBuf.Bytes()
+}
+
 func (s *service) getSystemDiscovery(w http.ResponseWriter, _ *http.Request) {
 	devices := make(map[string]discover.CacheEntry)
 
@@ -1946,7 +1953,8 @@ func sanitizedHostname(name string) (string, error) {
 			return r > unicode.MaxASCII ||
 				!unicode.IsLetter(r) && !unicode.IsNumber(r) &&
 					r != '.' && r != '-'
-		})))
+		})),
+	)
 	name, _, err := transform.String(t, name)
 	if err != nil {
 		return "", err

lib/api/api_test.go

@@ -1829,6 +1829,14 @@ func TestSanitizedHostname(t *testing.T) {
 	}
 }
 
+func TestPrometheusMetrics(t *testing.T) {
+	// We should get some form of reasonable metrics response
+	bs := prometheusMetrics()
+	if !bytes.Contains(bs, []byte("TYPE go_info gauge")) {
+		t.Error("metrics should include go_info gauge")
+	}
+}
+
 // runningInContainer returns true if we are inside Docker or LXC. It might
 // be prone to false negatives if things change in the future, but likely
 // not false positives.