From edf7ed614e41ba355c6f85ebad36729dc8be40c7 Mon Sep 17 00:00:00 2001
From: Nishant Das <nishdas93@gmail.com>
Date: Thu, 5 Nov 2020 09:33:45 +0800
Subject: [PATCH] Reduce Hashing When Filling In Forkchoice Blocks (#7716)

* reduce hashing

* add in test

* Update beacon-chain/blockchain/process_block_test.go

Co-authored-by: terence tsao <terence@prysmaticlabs.com>
Co-authored-by: Victor Farazdagi <simple.square@gmail.com>
Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>
---
 .../blockchain/process_block_helpers.go       |  9 ++--
 beacon-chain/blockchain/process_block_test.go | 41 +++++++++++++++++++
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/beacon-chain/blockchain/process_block_helpers.go b/beacon-chain/blockchain/process_block_helpers.go
index f8967fcd53..b8b80c9137 100644
--- a/beacon-chain/blockchain/process_block_helpers.go
+++ b/beacon-chain/blockchain/process_block_helpers.go
@@ -363,6 +363,7 @@ func (s *Service) finalizedImpliesNewJustified(ctx context.Context, state *state
 func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk *ethpb.BeaconBlock,
 	fCheckpoint, jCheckpoint *ethpb.Checkpoint) error {
 	pendingNodes := make([]*ethpb.BeaconBlock, 0)
+	pendingRoots := make([][32]byte, 0)
 
 	parentRoot := bytesutil.ToBytes32(blk.ParentRoot)
 	slot := blk.Slot
@@ -380,6 +381,8 @@ func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk *ethpb.
 		}
 
 		pendingNodes = append(pendingNodes, b.Block)
+		copiedRoot := parentRoot
+		pendingRoots = append(pendingRoots, copiedRoot)
 		parentRoot = bytesutil.ToBytes32(b.Block.ParentRoot)
 		slot = b.Block.Slot
 		higherThanFinalized = slot > fSlot
@@ -389,11 +392,7 @@ func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk *ethpb.
 	// Lower slots should be at the end of the list.
 	for i := len(pendingNodes) - 1; i >= 0; i-- {
 		b := pendingNodes[i]
-		r, err := b.HashTreeRoot()
-		if err != nil {
-			return err
-		}
-
+		r := pendingRoots[i]
 		if err := s.forkChoiceStore.ProcessBlock(ctx,
 			b.Slot, r, bytesutil.ToBytes32(b.ParentRoot), bytesutil.ToBytes32(b.Body.Graffiti),
 			jCheckpoint.Epoch,
diff --git a/beacon-chain/blockchain/process_block_test.go b/beacon-chain/blockchain/process_block_test.go
index 69e81b2546..eb38c8d1a1 100644
--- a/beacon-chain/blockchain/process_block_test.go
+++ b/beacon-chain/blockchain/process_block_test.go
@@ -2,6 +2,7 @@ package blockchain
 
 import (
 	"context"
+	"fmt"
 	"testing"
 	"time"
 
@@ -372,6 +373,46 @@ func TestFillForkChoiceMissingBlocks_CanSave(t *testing.T) {
 	assert.Equal(t, true, service.forkChoiceStore.HasNode(bytesutil.ToBytes32(roots[8])), "Didn't save node")
 }
 
+func TestFillForkChoiceMissingBlocks_RootsMatch(t *testing.T) {
+	ctx := context.Background()
+	db, _ := testDB.SetupDB(t)
+
+	cfg := &Config{BeaconDB: db}
+	service, err := NewService(ctx, cfg)
+	require.NoError(t, err)
+	service.forkChoiceStore = protoarray.New(0, 0, [32]byte{'A'})
+	service.finalizedCheckpt = &ethpb.Checkpoint{Root: make([]byte, 32)}
+
+	genesisStateRoot := [32]byte{}
+	genesis := blocks.NewGenesisBlock(genesisStateRoot[:])
+	require.NoError(t, db.SaveBlock(ctx, genesis))
+	validGenesisRoot, err := genesis.Block.HashTreeRoot()
+	require.NoError(t, err)
+	st := testutil.NewBeaconState()
+
+	require.NoError(t, service.beaconDB.SaveState(ctx, st.Copy(), validGenesisRoot))
+	roots, err := blockTree1(db, validGenesisRoot[:])
+	require.NoError(t, err)
+
+	beaconState, _ := testutil.DeterministicGenesisState(t, 32)
+	block := testutil.NewBeaconBlock()
+	block.Block.Slot = 9
+	block.Block.ParentRoot = roots[8]
+
+	err = service.fillInForkChoiceMissingBlocks(
+		context.Background(), block.Block, beaconState.FinalizedCheckpoint(), beaconState.CurrentJustifiedCheckpoint())
+	require.NoError(t, err)
+
+	// 5 nodes from the block tree 1. B0 - B3 - B4 - B6 - B8
+	assert.Equal(t, 5, len(service.forkChoiceStore.Nodes()), "Miss match nodes")
+	// Ensure all roots and their respective blocks exist.
+	wantedRoots := [][]byte{roots[0], roots[3], roots[4], roots[6], roots[8]}
+	for i, rt := range wantedRoots {
+		assert.Equal(t, true, service.forkChoiceStore.HasNode(bytesutil.ToBytes32(rt)), fmt.Sprintf("Didn't save node: %d", i))
+		assert.Equal(t, true, service.beaconDB.HasBlock(context.Background(), bytesutil.ToBytes32(rt)))
+	}
+}
+
 func TestFillForkChoiceMissingBlocks_FilterFinalized(t *testing.T) {
 	ctx := context.Background()
 	db, _ := testDB.SetupDB(t)