Update Slices More Efficiently (#4789)

* better cached states

* lint

* jim's review

beacon-chain/blockchain/chain_info.go

@@ -22,6 +22,12 @@ type ChainInfoFetcher interface {
 	FinalizationFetcher
 }
 
+// ChainCleaner describes an interface to clean obsolete data
+// stored in the blockchain service.
+type ChainCleaner interface {
+	ClearCachedStates()
+}
+
 // TimeFetcher retrieves the Eth2 data that's related to time.
 type TimeFetcher interface {
 	GenesisTime() time.Time

beacon-chain/blockchain/service.go

@@ -269,6 +269,12 @@ func (s *Service) Status() error {
 	return nil
 }
 
+// ClearCachedStates removes all stored caches states. This is done after the node
+// is synced.
+func (s *Service) ClearCachedStates() {
+	s.initSyncState = map[[32]byte]*stateTrie.BeaconState{}
+}
+
 // This gets called to update canonical root mapping.
 func (s *Service) saveHead(ctx context.Context, signed *ethpb.SignedBeaconBlock, r [32]byte) error {
 	s.headLock.Lock()

beacon-chain/blockchain/testing/mock.go

@@ -231,3 +231,8 @@ func (ms *ChainService) Participation(epoch uint64) *precompute.Balance {
 func (ms *ChainService) IsValidAttestation(ctx context.Context, att *ethpb.Attestation) bool {
 	return ms.ValidAttestation
 }
+
+// ClearCachedStates is a no-op.
+func (ms *ChainService) ClearCachedStates() {
+	// no-op
+}

beacon-chain/state/setters.go

@@ -106,7 +106,9 @@ func (b *BeaconState) UpdateBlockRootAtIndex(idx uint64, blockRoot [32]byte) err
 	r := b.state.BlockRoots
 	if ref := b.sharedFieldReferences[blockRoots]; ref.refs > 1 {
 		// Copy on write since this is a shared array.
-		r = b.BlockRoots()
+		newRoots := make([][]byte, len(r))
+		copy(newRoots, r)
+		r = newRoots
 
 		ref.refs--
 		b.sharedFieldReferences[blockRoots] = &reference{refs: 1}
@@ -150,7 +152,9 @@ func (b *BeaconState) UpdateStateRootAtIndex(idx uint64, stateRoot [32]byte) err
 	r := b.state.StateRoots
 	if ref := b.sharedFieldReferences[stateRoots]; ref.refs > 1 {
 		// Perform a copy since this is a shared reference and we don't want to mutate others.
-		r = b.StateRoots()
+		newRoots := make([][]byte, len(r))
+		copy(newRoots, r)
+		r = newRoots
 
 		ref.refs--
 		b.sharedFieldReferences[stateRoots] = &reference{refs: 1}
@@ -289,8 +293,9 @@ func (b *BeaconState) UpdateValidatorAtIndex(idx uint64, val *ethpb.Validator) e
 	v := b.state.Validators
 	if ref := b.sharedFieldReferences[validators]; ref.refs > 1 {
 		// Perform a copy since this is a shared reference and we don't want to mutate others.
-		v = b.Validators()
-
+		newVals := make([]*ethpb.Validator, len(v))
+		copy(newVals, v)
+		v = newVals
 		ref.refs--
 		b.sharedFieldReferences[validators] = &reference{refs: 1}
 	}
@@ -381,7 +386,9 @@ func (b *BeaconState) UpdateRandaoMixesAtIndex(val []byte, idx uint64) error {
 	b.lock.RLock()
 	mixes := b.state.RandaoMixes
 	if refs := b.sharedFieldReferences[randaoMixes].refs; refs > 1 {
-		mixes = b.RandaoMixes()
+		newSlice := make([][]byte, len(mixes))
+		copy(newSlice, mixes)
+		mixes = newSlice
 		b.sharedFieldReferences[randaoMixes].refs--
 		b.sharedFieldReferences[randaoMixes] = &reference{refs: 1}
 	}

beacon-chain/sync/initial-sync/service.go

@@ -25,6 +25,7 @@ var _ = shared.Service(&Service{})
 type blockchainService interface {
 	blockchain.BlockReceiver
 	blockchain.HeadFetcher
+	blockchain.ChainCleaner
 }
 
 const (
@@ -129,6 +130,7 @@ func (s *Service) Start() {
 	}
 	log.Infof("Synced up to slot %d", s.chain.HeadSlot())
 	s.synced = true
+	s.chain.ClearCachedStates()
 }
 
 // Stop initial sync.
@@ -167,6 +169,7 @@ func (s *Service) Resync() error {
 		log = log.WithError(err)
 	}
 	log.WithField("slot", s.chain.HeadSlot()).Info("Resync attempt complete")
+	s.chain.ClearCachedStates()
 
 	return nil
 }