dex: fix fast sync in BP mode (#291)

Start blockproposer only after fast sync is completed (received
ChainHead event), so watchcat is not falsely triggered.

1 files changed, 14 insertions, 1 deletions

diff --git a/dex/backend.go b/dex/backend.go
index f1b0012a2..29ac42906 100644
--- a/dex/backend.go
+++ b/dex/backend.go
@@ -253,7 +253,20 @@ func (s *Dexon) Start(srvr *p2p.Server) error {
 	s.protocolManager.Start(srvr, maxPeers)
 
 	if s.config.BlockProposerEnabled {
-		s.bp.Start()
+		go func() {
+			// Since we might be in fast sync mode when started. wait for
+			// ChainHeadEvent before starting blockproposer, or else we will trigger
+			// watchcat.
+			if s.config.SyncMode == downloader.FastSync &&
+				s.blockchain.CurrentBlock().NumberU64() == 0 {
+				ch := make(chan core.ChainHeadEvent)
+				sub := s.blockchain.SubscribeChainHeadEvent(ch)
+				defer sub.Unsubscribe()
+
+				<-ch
+			}
+			s.bp.Start()
+		}()
 	}
 	return nil
 }