server: removed lock, added second check to prevent multiple log outputs

server/service.go

@@ -662,17 +662,20 @@ func (m *BoostService) processDenebPayload(w http.ResponseWriter, req *http.Requ
 	headers := map[string]string{HeaderKeySlotUID: currentSlotUID}
 
 	// Prepare for requests
-	var wg sync.WaitGroup
 	resultCh := make(chan *builderApi.VersionedSubmitBlindedBlockResponse, len(m.relays))
+	var received atomic.Bool
+	go func() {
+		// Make sure we receive a response within the timeout
+		time.Sleep(m.httpClientGetPayload.Timeout)
+		resultCh <- nil
+	}()
 
 	// Prepare the request context, which will be cancelled after the first successful response from a relay
 	requestCtx, requestCtxCancel := context.WithCancel(context.Background())
 	defer requestCtxCancel()
 
 	for _, relay := range m.relays {
-		wg.Add(1)
 		go func(relay types.RelayEntry) {
-			defer wg.Done()
 			url := relay.GetURI(params.PathGetPayload)
 			log := log.WithField("url", url)
 			log.Debug("calling getPayload")
@@ -728,14 +731,16 @@ func (m *BoostService) processDenebPayload(w http.ResponseWriter, req *http.Requ
 			}
 
 			requestCtxCancel()
-			resultCh <- responsePayload
-			log.Info("received payload from relay")
+			if received.CompareAndSwap(true, true) {
+				log.Trace("Discarding response, already received a correct response")
+			} else {
+				resultCh <- responsePayload
+				log.Info("received payload from relay")
+			}
 		}(relay)
 	}
 
-	// Wait for all requests to complete...
-	wg.Wait()
-	close(resultCh)
+	// Wait for the first request to complete
 	result := <-resultCh
 
 	// If no payload has been received from relay, log loudly about withholding!