Fix pending block index during startup.

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

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,

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 {