Create Error State Interface

Added error checking functions in transactionSyncer.go for syncer's
error state get/set/reset.

pkg/neg/manager_test.go

@@ -1535,6 +1535,7 @@ func (s *fakeSyncer) Stop()                {}
 func (s *fakeSyncer) Sync() bool           { return s.syncFunc() }
 func (s *fakeSyncer) IsStopped() bool      { return s.isStopped }
 func (s *fakeSyncer) IsShuttingDown() bool { return false }
+func (s *fakeSyncer) InErrorState() bool   { return false }
 
 // getNegObjectRefs generates the NegObjectReference list of all negs with the specified negName in the specified zones
 func getNegObjectRefs(t *testing.T, cloud negtypes.NetworkEndpointGroupCloud, zones []string, negName string, version meta.Version) []negv1beta1.NegObjectReference {

pkg/neg/syncers/syncer.go

@@ -31,6 +31,9 @@ import (
 
 type syncerCore interface {
 	sync() error
+	inErrorState() bool
+	setErrorState()
+	resetErrorState()
 }
 
 // syncer is a NEG syncer skeleton.
@@ -164,3 +167,7 @@ func (s *syncer) IsShuttingDown() bool {
 	defer s.stateLock.Unlock()
 	return s.shuttingDown
 }
+
+func (s *syncer) InErrorState() bool {
+	return s.core.inErrorState()
+}

pkg/neg/syncers/syncer_test.go

@@ -77,6 +77,12 @@ func (t *syncerTester) sync() error {
 	return nil
 }
 
+func (t *syncerTester) inErrorState() bool { return false }
+
+func (t *syncerTester) setErrorState() {}
+
+func (t *syncerTester) resetErrorState() {}
+
 func newSyncerTester() *syncerTester {
 	testNegName := "test-neg-name"
 	testContext := negtypes.NewTestContext()

pkg/neg/syncers/transaction.go

@@ -176,6 +176,11 @@ func (s *transactionSyncer) sync() error {
 }
 
 func (s *transactionSyncer) syncInternal() error {
+	// TODO: enter degraded mode before reset and sync
+	if s.inErrorState() {
+		s.resetErrorState()
+	}
+
 	s.syncLock.Lock()
 	defer s.syncLock.Unlock()
 

pkg/neg/types/interfaces.go

@@ -61,6 +61,8 @@ type NegSyncer interface {
 	IsStopped() bool
 	// IsShuttingDown returns true if syncer is shutting down
 	IsShuttingDown() bool
+	// InErrorState returns true if syncer is in error state
+	InErrorState() bool
 }
 
 // NegSyncerManager is an interface for controllers to manage syncer