Remove outputs blocking inputs when output is slow (#4938)

plugins/outputs/prometheus_client/prometheus_client.go

@@ -144,7 +144,7 @@ func (p *PrometheusClient) auth(h http.Handler) http.Handler {
 	})
 }
 
-func (p *PrometheusClient) Start() error {
+func (p *PrometheusClient) Connect() error {
 	defaultCollectors := map[string]bool{
 		"gocollector": true,
 		"process":     true,
@@ -200,15 +200,6 @@ func (p *PrometheusClient) Start() error {
 	return nil
 }
 
-func (p *PrometheusClient) Stop() {
-	// plugin gets cleaned up in Close() already.
-}
-
-func (p *PrometheusClient) Connect() error {
-	// This service output does not need to make any further connections
-	return nil
-}
-
 func (p *PrometheusClient) Close() error {
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
 	defer cancel()

plugins/outputs/prometheus_client/prometheus_client_test.go

@@ -600,7 +600,7 @@ func TestPrometheusWritePointEmptyTag(t *testing.T) {
 
 	pClient, p, err := setupPrometheus()
 	require.NoError(t, err)
-	defer pClient.Stop()
+	defer pClient.Close()
 
 	now := time.Now()
 	tags := make(map[string]string)
@@ -675,7 +675,7 @@ func setupPrometheus() (*PrometheusClient, *prometheus_input.Prometheus, error)
 		pTesting = NewClient()
 		pTesting.Listen = "localhost:9127"
 		pTesting.Path = "/metrics"
-		err := pTesting.Start()
+		err := pTesting.Connect()
 		if err != nil {
 			return nil, nil, err
 		}