From 33ea179b60b51c5ad66b84065f6aec01bf6bfc1b Mon Sep 17 00:00:00 2001
From: Leo Chen <leo@harmony.one>
Date: Mon, 18 May 2020 10:48:14 -0700
Subject: [PATCH] Revert "make crosslink broadcast smarter and more efficient
 (#3036)"

This reverts commit afa6ce3d5fa23b4b0a624a60a6f9637587830910.
---
 node/node_cross_link.go |  2 +-
 node/node_handler.go    | 45 +++++++++++------------------------------
 node/node_syncing.go    |  4 ----
 3 files changed, 13 insertions(+), 38 deletions(-)

diff --git a/node/node_cross_link.go b/node/node_cross_link.go
index f0fdff560..98852b25d 100644
--- a/node/node_cross_link.go
+++ b/node/node_cross_link.go
@@ -91,7 +91,7 @@ func (node *Node) ProcessCrossLinkMessage(msgPayload []byte) {
 			Msgf("[ProcessingCrossLink] Received crosslinks: %d", len(crosslinks))
 
 		for i, cl := range crosslinks {
-			if i > crossLinkBatchSize*10 { // A sanity check to prevent spamming
+			if i > crossLinkBatchSize {
 				break
 			}
 
diff --git a/node/node_handler.go b/node/node_handler.go
index ea6b70a74..fbcfde02e 100644
--- a/node/node_handler.go
+++ b/node/node_handler.go
@@ -236,18 +236,7 @@ func (node *Node) BroadcastSlash(witness *slash.Record) {
 
 // BroadcastCrossLink is called by consensus leader to
 // send the new header as cross link to beacon chain.
-func (node *Node) BroadcastCrossLink() {
-	curBlock := node.Blockchain().CurrentBlock()
-	if curBlock == nil {
-		return
-	}
-
-	if node.NodeConfig.ShardID == shard.BeaconChainShardID ||
-		!node.Blockchain().Config().IsCrossLink(curBlock.Epoch()) {
-		// no need to broadcast crosslink if it's beacon chain or it's not crosslink epoch
-		return
-	}
-
+func (node *Node) BroadcastCrossLink(newBlock *types.Block) {
 	// no point to broadcast the crosslink if we aren't even in the right epoch yet
 	if !node.Blockchain().Config().IsCrossLink(
 		node.Blockchain().CurrentHeader().Epoch(),
@@ -260,50 +249,36 @@ func (node *Node) BroadcastCrossLink() {
 		nodeconfig.NewGroupIDByShardID(shard.BeaconChainShardID),
 	)
 	headers := []*block.Header{}
-	lastLink, err := node.Beaconchain().ReadShardLastCrossLink(curBlock.ShardID())
+	lastLink, err := node.Beaconchain().ReadShardLastCrossLink(newBlock.ShardID())
 	var latestBlockNum uint64
 
 	// TODO chao: record the missing crosslink in local database instead of using latest crosslink
 	// if cannot find latest crosslink, broadcast latest 3 block headers
 	if err != nil {
 		utils.Logger().Debug().Err(err).Msg("[BroadcastCrossLink] ReadShardLastCrossLink Failed")
-		header := node.Blockchain().GetHeaderByNumber(curBlock.NumberU64() - 2)
+		header := node.Blockchain().GetHeaderByNumber(newBlock.NumberU64() - 2)
 		if header != nil && node.Blockchain().Config().IsCrossLink(header.Epoch()) {
 			headers = append(headers, header)
 		}
-		header = node.Blockchain().GetHeaderByNumber(curBlock.NumberU64() - 1)
+		header = node.Blockchain().GetHeaderByNumber(newBlock.NumberU64() - 1)
 		if header != nil && node.Blockchain().Config().IsCrossLink(header.Epoch()) {
 			headers = append(headers, header)
 		}
-		headers = append(headers, curBlock.Header())
+		headers = append(headers, newBlock.Header())
 	} else {
 		latestBlockNum = lastLink.BlockNum()
-
-		batchSize := crossLinkBatchSize
-		diff := curBlock.Number().Uint64() - latestBlockNum
-
-		if diff > 100 {
-			// Increase batch size by 1 for every 100 blocks beyond
-			batchSize += int(diff-100) / 100
-		}
-
-		// Cap at a sane size to avoid overload network
-		if batchSize > crossLinkBatchSize*10 {
-			batchSize = crossLinkBatchSize * 10
-		}
-
-		for blockNum := latestBlockNum + 1; blockNum <= curBlock.NumberU64(); blockNum++ {
+		for blockNum := latestBlockNum + 1; blockNum <= newBlock.NumberU64(); blockNum++ {
 			header := node.Blockchain().GetHeaderByNumber(blockNum)
 			if header != nil && node.Blockchain().Config().IsCrossLink(header.Epoch()) {
 				headers = append(headers, header)
-				if len(headers) == batchSize {
+				if len(headers) == crossLinkBatchSize {
 					break
 				}
 			}
 		}
 	}
 
-	utils.Logger().Info().Msgf("[BroadcastCrossLink] Broadcasting Block Headers, latestBlockNum %d, currentBlockNum %d, Number of Headers %d", latestBlockNum, curBlock.NumberU64(), len(headers))
+	utils.Logger().Info().Msgf("[BroadcastCrossLink] Broadcasting Block Headers, latestBlockNum %d, currentBlockNum %d, Number of Headers %d", latestBlockNum, newBlock.NumberU64(), len(headers))
 	for _, header := range headers {
 		utils.Logger().Debug().Msgf(
 			"[BroadcastCrossLink] Broadcasting %d",
@@ -444,6 +419,10 @@ func (node *Node) PostConsensusProcessing(
 		if node.NodeConfig.ShardID == shard.BeaconChainShardID {
 			node.BroadcastNewBlock(newBlock)
 		}
+		if node.NodeConfig.ShardID != shard.BeaconChainShardID &&
+			node.Blockchain().Config().IsCrossLink(newBlock.Epoch()) {
+			node.BroadcastCrossLink(newBlock)
+		}
 		node.BroadcastCXReceipts(newBlock)
 	} else {
 		if node.Consensus.Mode() != consensus.Listening {
diff --git a/node/node_syncing.go b/node/node_syncing.go
index c991c7b0b..641e27b11 100644
--- a/node/node_syncing.go
+++ b/node/node_syncing.go
@@ -168,10 +168,6 @@ func (node *Node) DoBeaconSyncing() {
 				)
 				if err != nil {
 					node.beaconSync.AddLastMileBlock(beaconBlock)
-					if node.Consensus.IsLeader() {
-						// Only leader broadcast crosslink to avoid spamming p2p
-						node.BroadcastCrossLink()
-					}
 				}
 			}
 		}