From f5c393506d49a123900f88815c6bb2b61765a8eb Mon Sep 17 00:00:00 2001
From: Cedric Fung <cedric@vec.io>
Date: Tue, 5 Mar 2019 12:39:31 +0800
Subject: [PATCH] check node sync status before sign self snapshot

---
 kernel/graph.go |  2 +-
 kernel/node.go  | 17 ++++++++++++++++-
 kernel/self.go  | 11 ++++++++---
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/kernel/graph.go b/kernel/graph.go
index 4d3eaa141..a730769fe 100644
--- a/kernel/graph.go
+++ b/kernel/graph.go
@@ -21,7 +21,7 @@ func (node *Node) handleSnapshotInput(s *common.Snapshot) error {
 		return node.handleSyncFinalSnapshot(s)
 	}
 
-	if !node.CheckSync() {
+	if !node.CheckCatchUp() {
 		return node.queueSnapshotOrPanic(s, false)
 	}
 
diff --git a/kernel/node.go b/kernel/node.go
index a0606c370..e308e5947 100644
--- a/kernel/node.go
+++ b/kernel/node.go
@@ -267,7 +267,7 @@ func (node *Node) QueueAppendSnapshot(peerId crypto.Hash, s *common.Snapshot) er
 	if !signersMap[peerId] {
 		return nil
 	}
-	if !node.CheckSync() {
+	if !node.CheckCatchUp() {
 		return nil
 	}
 	return node.store.QueueAppendSnapshot(peerId, s, false)
@@ -311,6 +311,21 @@ func (node *Node) UpdateSyncPoint(peerId crypto.Hash, points []*network.SyncPoin
 }
 
 func (node *Node) CheckSync() bool {
+	count := 1
+	final := node.Graph.MyFinalNumber
+	for id, _ := range node.ConsensusNodes {
+		remote := node.SyncPoints.Get(id)
+		if remote == nil {
+			continue
+		}
+		if remote.Number+1 >= final {
+			count += 1
+		}
+	}
+	return count >= len(node.ConsensusNodes)*2/3+1
+}
+
+func (node *Node) CheckCatchUp() bool {
 	if node.SyncPoints.Len() != len(node.ConsensusNodes)-1 {
 		return false
 	}
diff --git a/kernel/self.go b/kernel/self.go
index f52a9491a..477f5823b 100644
--- a/kernel/self.go
+++ b/kernel/self.go
@@ -138,13 +138,18 @@ func (node *Node) signSelfSnapshot(s *common.Snapshot, tx *common.SignedTransact
 	if s.NodeId != node.IdForNetwork || len(s.Signatures) != 0 || s.Timestamp != 0 {
 		panic("should never be here")
 	}
+
+	cache := node.Graph.CacheRound[s.NodeId].Copy()
+	final := node.Graph.FinalRound[s.NodeId].Copy()
+
 	if !node.checkCacheCapability() {
 		time.Sleep(10 * time.Millisecond)
 		return node.queueSnapshotOrPanic(s, false)
 	}
-
-	cache := node.Graph.CacheRound[s.NodeId].Copy()
-	final := node.Graph.FinalRound[s.NodeId].Copy()
+	if !node.CheckSync() && len(cache.Snapshots) == 0 {
+		time.Sleep(time.Duration(config.SnapshotRoundGap / 2))
+		return node.queueSnapshotOrPanic(s, false)
+	}
 
 	for {
 		s.Timestamp = uint64(time.Now().UnixNano())