From d35f12b85adf51dee65601d2840253cdd4321561 Mon Sep 17 00:00:00 2001
From: Minh Doan <minh@simple-rules.com>
Date: Wed, 21 Nov 2018 18:04:04 -0800
Subject: [PATCH] state sync improvement

---
 syncing/syncing.go | 86 +++++++++++++++++++++++++++++++---------------
 1 file changed, 58 insertions(+), 28 deletions(-)

diff --git a/syncing/syncing.go b/syncing/syncing.go
index dee3717c0..b56d40d10 100644
--- a/syncing/syncing.go
+++ b/syncing/syncing.go
@@ -3,6 +3,7 @@ package syncing
 import (
 	"bufio"
 	"net"
+	"reflect"
 	"sync"
 	"time"
 
@@ -40,9 +41,11 @@ func GetStateSync() *StateSync {
 
 // StateSync is the struct that implements StateSyncInterface.
 type StateSync struct {
-	peerNumber       int
-	activePeerNumber int
-	syncConfig       *SyncConfig
+	peerNumber         int
+	activePeerNumber   int
+	blockHeight        int
+	syncConfig         *SyncConfig
+	stateSyncTaskQueue *queue.Queue
 }
 
 // ProcessStateSyncFromPeers used to do state sync.
@@ -94,16 +97,24 @@ func (ss *StateSync) makeConnectionToPeers() {
 	}
 }
 
-// StartStateSync starts state sync.
-func (ss *StateSync) StartStateSync(peers []p2p.Peer, bc *blockchain.Blockchain) {
-	// Create sync config.
-	ss.createSyncConfig(peers)
-
-	// Make connections to peers.
-	ss.makeConnectionToPeers()
+// areConsensusHashesEqual chesk if all consensus hashes are equal.
+func (ss *StateSync) areConsensusHashesEqual() bool {
+	var fixedPeer *SyncPeerConfig
+	for _, configPeer := range ss.syncConfig.peers {
+		if configPeer.trusted {
+			if fixedPeer == nil {
+				fixedPeer = &configPeer
+			}
+			if !reflect.DeepEqual(configPeer.blockHashes, fixedPeer) {
+				return false
+			}
+		}
+	}
+	return true
+}
 
-	// Looping to get an array of block hashes from honest nodes.
-LOOP_HONEST_NODE:
+// getConsensusHashes gets all hashes needed to download.
+func (ss *StateSync) getConsensusHashes() {
 	for {
 		var wg sync.WaitGroup
 		wg.Add(ss.activePeerNumber)
@@ -132,37 +143,39 @@ LOOP_HONEST_NODE:
 				peerConfig.blockHashes = blockchainSyncMessage.BlockHashes
 			}(&configPeer)
 		}
-		wg.Wait()
-
-		if getConsensus(ss.syncConfig) {
-			break LOOP_HONEST_NODE
+		if ss.areConsensusHashesEqual() {
+			break
 		}
 	}
+}
 
-	taskSyncQueue := queue.New(0)
-	blockSize := 0
-TASK_LOOP:
+// getConsensusHashes gets all hashes needed to download.
+func (ss *StateSync) generateStateSyncTaskQueue() {
+	ss.stateSyncTaskQueue = queue.New(0)
 	for _, configPeer := range ss.syncConfig.peers {
 		if configPeer.trusted {
 			for id, blockHash := range configPeer.blockHashes {
-				taskSyncQueue.Put(SyncBlockTask{index: id, blockHash: blockHash})
+				ss.stateSyncTaskQueue.Put(SyncBlockTask{index: id, blockHash: blockHash})
 			}
-			blockSize = len(configPeer.blockHashes)
-			break TASK_LOOP
+			ss.blockHeight = len(configPeer.blockHashes)
 		}
 	}
+}
+
+// downloadBlocks downloads blocks from state sync task queue.
+func (ss *StateSync) downloadBlocks(bc *blockchain.Blockchain) {
 	// Initialize blockchain
-	bc.Blocks = make([]*blockchain.Block, blockSize)
+	bc.Blocks = make([]*blockchain.Block, ss.blockHeight)
 	var wg sync.WaitGroup
-	wg.Add(ss.activePeerNumber)
+	wg.Add(int(ss.stateSyncTaskQueue.Len()))
 	for _, configPeer := range ss.syncConfig.peers {
 		if configPeer.err != nil {
 			continue
 		}
-		go func(peerConfig *SyncPeerConfig, taskSyncQueue *queue.Queue, bc *blockchain.Blockchain) {
+		go func(peerConfig *SyncPeerConfig, stateSyncTaskQueue *queue.Queue, bc *blockchain.Blockchain) {
 			defer wg.Done()
-			for !taskSyncQueue.Empty() {
-				task, err := taskSyncQueue.Poll(1, time.Millisecond)
+			for !stateSyncTaskQueue.Empty() {
+				task, err := stateSyncTaskQueue.Poll(1, time.Millisecond)
 				if err == queue.ErrTimeout {
 					break
 				}
@@ -181,11 +194,28 @@ TASK_LOOP:
 					bc.Blocks[syncTask.index] = block
 				}
 			}
-		}(&configPeer, taskSyncQueue, bc)
+		}(&configPeer, ss.stateSyncTaskQueue, bc)
 	}
 	wg.Wait()
 }
 
+// StartStateSync starts state sync.
+func (ss *StateSync) StartStateSync(peers []p2p.Peer, bc *blockchain.Blockchain) {
+	// Creates sync config.
+	ss.createSyncConfig(peers)
+
+	// Makes connections to peers.
+	ss.makeConnectionToPeers()
+
+	// Gets consensus hashes.
+	ss.getConsensusHashes()
+
+	// Generates state-sync task queue.
+	ss.generateStateSyncTaskQueue()
+
+	ss.downloadBlocks(bc)
+}
+
 func getConsensus(syncConfig *SyncConfig) bool {
 	return true
 }