feat: error metrics

README.md

@@ -117,7 +117,7 @@ You can specify a port for the iperf3 server target. If its not set, it will use
 ## Exposed metrics
 
 | name                                     | type    |
-| ---------------------------------------- | ----- |
+| ---------------------------------------- | ------- |
 | iperf3_download_sent_bits_per_second     | gauge   |
 | iperf3_download_sent_seconds             | gauge   |
 | iperf3_download_sent_bytes               | gauge   |
@@ -132,3 +132,4 @@ You can specify a port for the iperf3 server target. If its not set, it will use
 | iperf3_upload_received_bits_per_second   | gauge   |
 | iperf3_upload_received_seconds           | gauge   |
 | iperf3_upload_received_bytes             | gauge   |
+| iperf3_errors                            | counter |

main.go

@@ -89,6 +89,8 @@ var (
 	uploadReceivedBytes         = metrics.NewFloatCounter("iperf3_upload_received_bytes")
 )
 
+var scrapeErrors = metrics.NewCounter("iperf3_errors")
+
 //nolint:tagliatelle
 type iperfResult struct {
 	End struct {
@@ -255,6 +257,7 @@ func probeHandler(w http.ResponseWriter, r *http.Request) {
 	// Extract port and host for target.
 	t, err := NewTarget(trgt)
 	if err != nil {
+		scrapeErrors.Inc()
 		logger.Error().Err(err).Msg("could not determine target")
 		http.Error(w, "could not determine target", http.StatusUnprocessableEntity)
 	}