Fix address already in use with webhooks input during reload (#3206)

plugins/inputs/webhooks/webhooks.go

@@ -3,6 +3,7 @@ package webhooks
 import (
 	"fmt"
 	"log"
+	"net"
 	"net/http"
 	"reflect"
 
@@ -33,6 +34,8 @@ type Webhooks struct {
 	Mandrill   *mandrill.MandrillWebhook
 	Rollbar    *rollbar.RollbarWebhook
 	Papertrail *papertrail.PapertrailWebhook
+
+	srv *http.Server
 }
 
 func NewWebhooks() *Webhooks {
@@ -70,19 +73,6 @@ func (wb *Webhooks) Gather(_ telegraf.Accumulator) error {
 	return nil
 }
 
-func (wb *Webhooks) Listen(acc telegraf.Accumulator) {
-	r := mux.NewRouter()
-
-	for _, webhook := range wb.AvailableWebhooks() {
-		webhook.Register(r, acc)
-	}
-
-	err := http.ListenAndServe(fmt.Sprintf("%s", wb.ServiceAddress), r)
-	if err != nil {
-		acc.AddError(fmt.Errorf("E! Error starting server: %v", err))
-	}
-}
-
 // Looks for fields which implement Webhook interface
 func (wb *Webhooks) AvailableWebhooks() []Webhook {
 	webhooks := make([]Webhook, 0)
@@ -105,11 +95,35 @@ func (wb *Webhooks) AvailableWebhooks() []Webhook {
 }
 
 func (wb *Webhooks) Start(acc telegraf.Accumulator) error {
-	go wb.Listen(acc)
+	r := mux.NewRouter()
+
+	for _, webhook := range wb.AvailableWebhooks() {
+		webhook.Register(r, acc)
+	}
+
+	wb.srv = &http.Server{Handler: r}
+
+	ln, err := net.Listen("tcp", fmt.Sprintf("%s", wb.ServiceAddress))
+	if err != nil {
+		log.Fatalf("E! Error starting server: %v", err)
+		return err
+
+	}
+
+	go func() {
+		if err := wb.srv.Serve(ln); err != nil {
+			if err != http.ErrServerClosed {
+				acc.AddError(fmt.Errorf("E! Error listening: %v", err))
+			}
+		}
+	}()
+
 	log.Printf("I! Started the webhooks service on %s\n", wb.ServiceAddress)
+
 	return nil
 }
 
 func (rb *Webhooks) Stop() {
+	rb.srv.Close()
 	log.Println("I! Stopping the Webhooks service")
 }