From 1b8eb16fc7193d358441dc93cf1184dd39bbcc90 Mon Sep 17 00:00:00 2001
From: terence tsao <terence@prysmaticlabs.com>
Date: Sat, 7 Dec 2019 14:45:39 -0800
Subject: [PATCH] --initial-sync-cache-state don't need to save head root
 (#4219)

* Test

* Run time works

* Revert
---
 beacon-chain/blockchain/receive_block.go | 21 ++++++++++++++-----
 beacon-chain/blockchain/service.go       | 26 ++++++++++++++++++++++++
 beacon-chain/blockchain/service_test.go  | 23 +++++++++++++++++++++
 3 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/beacon-chain/blockchain/receive_block.go b/beacon-chain/blockchain/receive_block.go
index 685fd227f..75d556ea4 100644
--- a/beacon-chain/blockchain/receive_block.go
+++ b/beacon-chain/blockchain/receive_block.go
@@ -12,6 +12,7 @@ import (
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/feed"
 	statefeed "github.com/prysmaticlabs/prysm/beacon-chain/core/feed/state"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
+	"github.com/prysmaticlabs/prysm/shared/featureconfig"
 	"github.com/prysmaticlabs/prysm/shared/traceutil"
 	"github.com/sirupsen/logrus"
 	"go.opencensus.io/trace"
@@ -189,11 +190,21 @@ func (s *Service) ReceiveBlockNoVerify(ctx context.Context, block *ethpb.BeaconB
 		return errors.Wrap(err, "could not get signing root on received blockCopy")
 	}
 
-	if !bytes.Equal(root[:], s.HeadRoot()) {
-		if err := s.saveHead(ctx, blockCopy, root); err != nil {
-			err := errors.Wrap(err, "could not save head")
-			traceutil.AnnotateError(span, err)
-			return err
+	if featureconfig.Get().InitSyncCacheState {
+		if !bytes.Equal(root[:], s.HeadRoot()) {
+			if err := s.saveHeadNoDB(ctx, blockCopy, root); err != nil {
+				err := errors.Wrap(err, "could not save head")
+				traceutil.AnnotateError(span, err)
+				return err
+			}
+		}
+	} else {
+		if !bytes.Equal(root[:], s.HeadRoot()) {
+			if err := s.saveHead(ctx, blockCopy, root); err != nil {
+				err := errors.Wrap(err, "could not save head")
+				traceutil.AnnotateError(span, err)
+				return err
+			}
 		}
 	}
 
diff --git a/beacon-chain/blockchain/service.go b/beacon-chain/blockchain/service.go
index 14a8f6be2..ec9527e8b 100644
--- a/beacon-chain/blockchain/service.go
+++ b/beacon-chain/blockchain/service.go
@@ -255,6 +255,32 @@ func (s *Service) saveHead(ctx context.Context, b *ethpb.BeaconBlock, r [32]byte
 	return nil
 }
 
+// This gets called to update canonical root mapping. It does not save head block
+// root in DB. With the inception of inital-sync-cache-state flag, it uses finalized
+// check point as anchors to resume sync therefore head is no longer needed to be saved on per slot basis.
+func (s *Service) saveHeadNoDB(ctx context.Context, b *ethpb.BeaconBlock, r [32]byte) error {
+	s.headLock.Lock()
+	defer s.headLock.Unlock()
+
+	s.headSlot = b.Slot
+
+	s.canonicalRoots[b.Slot] = r[:]
+
+	s.headBlock = b
+
+	headState, err := s.beaconDB.State(ctx, r)
+	if err != nil {
+		return errors.Wrap(err, "could not retrieve head state in DB")
+	}
+	s.headState = headState
+
+	log.WithFields(logrus.Fields{
+		"slot":     b.Slot,
+		"headRoot": fmt.Sprintf("%#x", r),
+	}).Debug("Saved new head info")
+	return nil
+}
+
 // This gets called when beacon chain is first initialized to save validator indices and pubkeys in db
 func (s *Service) saveGenesisValidators(ctx context.Context, state *pb.BeaconState) error {
 	for i, v := range state.Validators {
diff --git a/beacon-chain/blockchain/service_test.go b/beacon-chain/blockchain/service_test.go
index 206324049..007d7b9cb 100644
--- a/beacon-chain/blockchain/service_test.go
+++ b/beacon-chain/blockchain/service_test.go
@@ -325,3 +325,26 @@ func TestChainService_InitializeChainInfo(t *testing.T) {
 		t.Error("head slot incorrect")
 	}
 }
+
+func TestChainService_SaveHeadNoDB(t *testing.T) {
+	db := testDB.SetupDB(t)
+	defer testDB.TeardownDB(t, db)
+	ctx := context.Background()
+	s := &Service{
+		beaconDB:       db,
+		canonicalRoots: make(map[uint64][]byte),
+	}
+	b := &ethpb.BeaconBlock{Slot: 1}
+	r, _ := ssz.SigningRoot(b)
+	if err := s.saveHeadNoDB(ctx, b, r); err != nil {
+		t.Fatal(err)
+	}
+
+	newB, err := s.beaconDB.HeadBlock(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if reflect.DeepEqual(newB, b) {
+		t.Error("head block should not be equal")
+	}
+}