From c2c5c6bde6ec74f8eda0b21316d6c504fe743a4c Mon Sep 17 00:00:00 2001
From: Ribao Wei <ribao@sliver.tv>
Date: Fri, 6 Dec 2019 17:20:32 -0800
Subject: [PATCH] Fix pending block index during startup.

---
 blockchain/chain.go | 9 +++++++++
 consensus/engine.go | 8 ++++++++
 netsync/request.go  | 3 +++
 3 files changed, 20 insertions(+)

diff --git a/blockchain/chain.go b/blockchain/chain.go
index 8653e2e3..cdeda8cb 100644
--- a/blockchain/chain.go
+++ b/blockchain/chain.go
@@ -114,6 +114,15 @@ func (ch *Chain) addBlock(block *core.Block, isSnapshotRoot bool) (*core.Extende
 	return extendedBlock, nil
 }
 
+// FixBlockIndex fixes index for given block.
+func (ch *Chain) FixBlockIndex(block *core.ExtendedBlock) {
+	ch.mu.Lock()
+	defer ch.mu.Unlock()
+
+	ch.AddBlockByHeightIndex(block.Height, block.Hash())
+	ch.AddTxsToIndex(block, false)
+}
+
 // blockByHeightIndexKey constructs the DB key for the given block height.
 func blockByHeightIndexKey(height uint64) common.Bytes {
 	// convert uint64 to []byte
diff --git a/consensus/engine.go b/consensus/engine.go
index c001e890..c06c4e93 100644
--- a/consensus/engine.go
+++ b/consensus/engine.go
@@ -329,6 +329,14 @@ func (e *ConsensusEngine) validateBlock(block *core.Block, parent *core.Extended
 		return result.Error("Block epoch must be greater than parent epoch")
 	}
 	if !parent.Status.IsValid() {
+		if parent.Status.IsPending() {
+			// Should never happen
+			e.logger.WithFields(log.Fields{
+				"parent":        block.Parent.Hex(),
+				"parent.status": parent.Status,
+				"block":         block.Hash().Hex(),
+			}).Panic("Parent block is pending")
+		}
 		e.logger.WithFields(log.Fields{
 			"parent":        block.Parent.Hex(),
 			"parent.status": parent.Status,
diff --git a/netsync/request.go b/netsync/request.go
index 957e308d..459f6ebb 100644
--- a/netsync/request.go
+++ b/netsync/request.go
@@ -661,6 +661,9 @@ func (rm *RequestManager) resumePendingBlocks() {
 		block := queue[0]
 		queue = queue[1:]
 		if block.Status.IsPending() {
+			// In rare cases a block is saved but index is not yet saved before the process is
+			// killed.
+			rm.chain.FixBlockIndex(block)
 			rm.addBlock(block.Block)
 		}
 		for _, hash := range block.Children {