From 7d669f23ab8071ac7da7ac0a090f91094377dd29 Mon Sep 17 00:00:00 2001
From: terence tsao <terence@prysmaticlabs.com>
Date: Mon, 4 Apr 2022 18:46:05 -0700
Subject: [PATCH] Sync: process pending block with optimistic parent  (#10480)

---
 beacon-chain/sync/pending_blocks_queue.go     |  8 +-
 .../sync/pending_blocks_queue_test.go         | 78 +++++++++++++++++++
 2 files changed, 83 insertions(+), 3 deletions(-)

diff --git a/beacon-chain/sync/pending_blocks_queue.go b/beacon-chain/sync/pending_blocks_queue.go
index 9dc4c64899..4f8641e7d9 100644
--- a/beacon-chain/sync/pending_blocks_queue.go
+++ b/beacon-chain/sync/pending_blocks_queue.go
@@ -152,14 +152,16 @@ func (s *Service) processPendingBlocks(ctx context.Context) error {
 				continue
 			}
 
-			if err := s.validateBeaconBlock(ctx, b, blkRoot); err != nil {
+			err = s.validateBeaconBlock(ctx, b, blkRoot)
+			switch {
+			case errors.Is(ErrOptimisticParent, err): // Ok to continue process block with parent that is an optimistic candidate.
+			case err != nil:
 				log.Debugf("Could not validate block from slot %d: %v", b.Block().Slot(), err)
 				s.setBadBlock(ctx, blkRoot)
 				tracing.AnnotateError(span, err)
-				// In the next iteration of the queue, this block will be removed from
-				// the pending queue as it has been marked as a 'bad' block.
 				span.End()
 				continue
+			default:
 			}
 
 			if err := s.cfg.chain.ReceiveBlock(ctx, b, blkRoot); err != nil {
diff --git a/beacon-chain/sync/pending_blocks_queue_test.go b/beacon-chain/sync/pending_blocks_queue_test.go
index 0034b7165a..52ba8fff42 100644
--- a/beacon-chain/sync/pending_blocks_queue_test.go
+++ b/beacon-chain/sync/pending_blocks_queue_test.go
@@ -111,6 +111,84 @@ func TestRegularSyncBeaconBlockSubscriber_ProcessPendingBlocks1(t *testing.T) {
 	assert.Equal(t, 2, len(r.seenPendingBlocks), "Incorrect size for seen pending block")
 }
 
+func TestRegularSyncBeaconBlockSubscriber_OptimisticStatus(t *testing.T) {
+	db := dbtest.SetupDB(t)
+
+	p1 := p2ptest.NewTestP2P(t)
+	r := &Service{
+		cfg: &config{
+			p2p:      p1,
+			beaconDB: db,
+			chain: &mock.ChainService{
+				Optimistic: true,
+				FinalizedCheckPoint: &ethpb.Checkpoint{
+					Epoch: 0,
+				},
+			},
+			stateGen: stategen.New(db),
+		},
+		slotToPendingBlocks: gcache.New(time.Second, 2*time.Second),
+		seenPendingBlocks:   make(map[[32]byte]bool),
+	}
+	r.initCaches()
+
+	b0 := util.NewBeaconBlock()
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b0)
+	require.NoError(t, err)
+	require.NoError(t, r.cfg.beaconDB.SaveBlock(context.Background(), wsb))
+	b0Root, err := b0.Block.HashTreeRoot()
+	require.NoError(t, err)
+	b3 := util.NewBeaconBlock()
+	b3.Block.Slot = 3
+	b3.Block.ParentRoot = b0Root[:]
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b3)
+	require.NoError(t, err)
+	require.NoError(t, r.cfg.beaconDB.SaveBlock(context.Background(), wsb))
+	// Incomplete block link
+	b1 := util.NewBeaconBlock()
+	b1.Block.Slot = 1
+	b1.Block.ParentRoot = b0Root[:]
+	b1Root, err := b1.Block.HashTreeRoot()
+	require.NoError(t, err)
+	b2 := util.NewBeaconBlock()
+	b2.Block.Slot = 2
+	b2.Block.ParentRoot = b1Root[:]
+	b2Root, err := b1.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	// Add b2 to the cache
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b2)
+	require.NoError(t, err)
+	require.NoError(t, r.insertBlockToPendingQueue(b2.Block.Slot, wsb, b2Root))
+
+	require.NoError(t, r.processPendingBlocks(context.Background()))
+	assert.Equal(t, 1, len(r.slotToPendingBlocks.Items()), "Incorrect size for slot to pending blocks cache")
+	assert.Equal(t, 1, len(r.seenPendingBlocks), "Incorrect size for seen pending block")
+
+	// Add b1 to the cache
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b1)
+	require.NoError(t, err)
+	require.NoError(t, r.insertBlockToPendingQueue(b1.Block.Slot, wsb, b1Root))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b1)
+	require.NoError(t, err)
+	require.NoError(t, r.cfg.beaconDB.SaveBlock(context.Background(), wsb))
+
+	nBlock := util.NewBeaconBlock()
+	nBlock.Block.Slot = b1.Block.Slot
+	nRoot, err := nBlock.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	// Insert bad b1 in the cache to verify the good one doesn't get replaced.
+	wsb, err = wrapper.WrappedSignedBeaconBlock(nBlock)
+	require.NoError(t, err)
+	require.NoError(t, r.insertBlockToPendingQueue(nBlock.Block.Slot, wsb, nRoot))
+	require.NoError(t, r.processPendingBlocks(context.Background())) // Marks a block as bad
+	require.NoError(t, r.processPendingBlocks(context.Background())) // Bad block removed on second run
+
+	assert.Equal(t, 1, len(r.slotToPendingBlocks.Items()), "Incorrect size for slot to pending blocks cache")
+	assert.Equal(t, 2, len(r.seenPendingBlocks), "Incorrect size for seen pending block")
+}
+
 func TestRegularSyncBeaconBlockSubscriber_ExecutionEngineTimesOut(t *testing.T) {
 	db := dbtest.SetupDB(t)