Refactor procedure to compute endpoint target map

Refactor the code that compute endpoint target map into a separate
function computeTargetMap.

pkg/neg/syncers/transaction.go

@@ -204,12 +204,6 @@ func (s *transactionSyncer) syncInternal() error {
 }
 
 func (s *transactionSyncer) syncInternalImpl() *negtypes.NegSyncResult {
-	// TODO(cheungdavid): for now we reset the boolean so it is a no-op, but
-	// in the future, it will be used to trigger degraded mode if the syncer is in error state.
-	if s.inErrorState() {
-		s.resetErrorState()
-	}
-
 	if s.needInit || s.isZoneChange() {
 		if err := s.ensureNetworkEndpointGroups(); err != nil {
 			return negtypes.NewNegSyncResult(err, negtypes.ResultNegNotFound)
@@ -236,7 +230,7 @@ func (s *transactionSyncer) syncInternalImpl() *negtypes.NegSyncResult {
 
 	var targetMap map[string]negtypes.NetworkEndpointSet
 	var endpointPodMap negtypes.EndpointPodMap
-	var dupCount int
+	var result *negtypes.NegSyncResult
 
 	if s.enableEndpointSlices {
 		slices, err := s.endpointSliceLister.ByIndex(endpointslices.EndpointSlicesByServiceIndex, endpointslices.FormatEndpointSlicesServiceKey(s.Namespace, s.Name))
@@ -268,18 +262,13 @@ func (s *transactionSyncer) syncInternalImpl() *negtypes.NegSyncResult {
 			s.logger.V(3).Info("Endpoint slice syncs", "Namespace", endpointslice.Namespace, "Name", endpointslice.Name, "staleness", epsStaleness)
 
 		}
-		endpointsData := negtypes.EndpointsDataFromEndpointSlices(endpointSlices)
-		targetMap, endpointPodMap, dupCount, err = s.endpointsCalculator.CalculateEndpoints(endpointsData, currentMap)
-		if valid, result := s.CheckEPField(err); !valid {
-			s.setErrorState(result.Result)
-			return result
-		}
-		if valid, result := s.CheckEndpointInfo(endpointsData, endpointPodMap, dupCount); !valid {
-			s.setErrorState(result.Result)
-			return result
-		}
-		if err != nil {
-			return negtypes.NewNegSyncResult(fmt.Errorf("endpoints calculation error in mode %q, err: %w", s.endpointsCalculator.Mode(), err), negtypes.ResultOtherError)
+		if s.inErrorState() {
+			s.resetErrorState()
+		} else {
+			targetMap, endpointPodMap, result = s.computeTargetMap(endpointSlices)
+			if result.Error != nil {
+				return result
+			}
 		}
 	} else {
 		ep, exists, err := s.endpointLister.Get(
@@ -333,6 +322,24 @@ func (s *transactionSyncer) syncInternalImpl() *negtypes.NegSyncResult {
 	return s.syncNetworkEndpoints(addEndpoints, removeEndpoints)
 }
 
+// computeTargetMap retrieve endpoint slices and compute the desire map
+func (s *transactionSyncer) computeTargetMap(endpointSlices []*discovery.EndpointSlice) (map[string]negtypes.NetworkEndpointSet, negtypes.EndpointPodMap, *negtypes.NegSyncResult) {
+	endpointsData := negtypes.EndpointsDataFromEndpointSlices(endpointSlices)
+	targetMap, endpointPodMap, dupCount, err := s.endpointsCalculator.CalculateEndpoints(endpointsData, nil)
+	var valid bool
+	var result *negtypes.NegSyncResult
+	if valid, result = s.CheckEPField(err); !valid {
+		s.setErrorState(result.Result)
+	}
+	if valid, result = s.CheckEndpointInfo(endpointsData, endpointPodMap, dupCount); !valid {
+		s.setErrorState(result.Result)
+	}
+	if result.Error != nil {
+		return nil, nil, result
+	}
+	return targetMap, endpointPodMap, negtypes.NewNegSyncResult(nil, negtypes.ResultSuccess)
+}
+
 // syncLock must already be acquired before execution
 func (s *transactionSyncer) inErrorState() bool {
 	return s.errorState != ""