core: minor code polishes + rebase fixes

core/blockchain.go

@@ -1465,17 +1465,21 @@ func (bc *BlockChain) insertSidechain(block *types.Block, it *insertIterator) (i
 	return 0, nil, nil, nil
 }
 
-// reorgs takes two blocks, an old chain and a new chain and will reconstruct the blocks and inserts them
-// to be part of the new canonical chain and accumulates potential missing transactions and post an
-// event about them
+// reorg takes two blocks, an old chain and a new chain and will reconstruct the
+// blocks and inserts them to be part of the new canonical chain and accumulates
+// potential missing transactions and post an event about them.
 func (bc *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 	var (
 		newChain    types.Blocks
 		oldChain    types.Blocks
 		commonBlock *types.Block
+
 		deletedTxs types.Transactions
+		addedTxs   types.Transactions
+
 		deletedLogs []*types.Log
 		rebirthLogs []*types.Log
+
 		// collectLogs collects the logs that were generated during the
 		// processing of the block that corresponds with the given hash.
 		// These logs are later announced as deleted or reborn
@@ -1498,46 +1502,49 @@ func (bc *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 			}
 		}
 	)
-
-	// first reduce whoever is higher bound
+	// Reduce the longer chain to the same number as the shorter one
 	if oldBlock.NumberU64() > newBlock.NumberU64() {
-		// reduce old chain
+		// Old chain is longer, gather all transactions and logs as deleted ones
 		for ; oldBlock != nil && oldBlock.NumberU64() != newBlock.NumberU64(); oldBlock = bc.GetBlock(oldBlock.ParentHash(), oldBlock.NumberU64()-1) {
 			oldChain = append(oldChain, oldBlock)
 			deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
-
 			collectLogs(oldBlock.Hash(), true)
 		}
 	} else {
-		// reduce new chain and append new chain blocks for inserting later on
+		// New chain is longer, stash all blocks away for subsequent insertion
 		for ; newBlock != nil && newBlock.NumberU64() != oldBlock.NumberU64(); newBlock = bc.GetBlock(newBlock.ParentHash(), newBlock.NumberU64()-1) {
 			newChain = append(newChain, newBlock)
 		}
 	}
 	if oldBlock == nil {
-		return fmt.Errorf("Invalid old chain")
+		return fmt.Errorf("invalid old chain")
 	}
 	if newBlock == nil {
-		return fmt.Errorf("Invalid new chain")
+		return fmt.Errorf("invalid new chain")
 	}
-
+	// Both sides of the reorg are at the same number, reduce both until the common
+	// ancestor is found
 	for {
+		// If the common ancestor was found, bail out
 		if oldBlock.Hash() == newBlock.Hash() {
 			commonBlock = oldBlock
 			break
 		}
-
+		// Remove an old block as well as stash away a new block
 		oldChain = append(oldChain, oldBlock)
-		newChain = append(newChain, newBlock)
 		deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
 		collectLogs(oldBlock.Hash(), true)
 
-		oldBlock, newBlock = bc.GetBlock(oldBlock.ParentHash(), oldBlock.NumberU64()-1), bc.GetBlock(newBlock.ParentHash(), newBlock.NumberU64()-1)
+		newChain = append(newChain, newBlock)
+
+		// Step back with both chains
+		oldBlock = bc.GetBlock(oldBlock.ParentHash(), oldBlock.NumberU64()-1)
 		if oldBlock == nil {
-			return fmt.Errorf("Invalid old chain")
+			return fmt.Errorf("invalid old chain")
 		}
+		newBlock = bc.GetBlock(newBlock.ParentHash(), newBlock.NumberU64()-1)
 		if newBlock == nil {
-			return fmt.Errorf("Invalid new chain")
+			return fmt.Errorf("invalid new chain")
 		}
 	}
 	// Ensure the user sees large reorgs
@@ -1552,42 +1559,46 @@ func (bc *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 		log.Error("Impossible reorg, please file an issue", "oldnum", oldBlock.Number(), "oldhash", oldBlock.Hash(), "newnum", newBlock.Number(), "newhash", newBlock.Hash())
 	}
 	// Insert the new chain, taking care of the proper incremental order
-	var addedTxs types.Transactions
 	for i := len(newChain) - 1; i >= 0; i-- {
-		// insert the block in the canonical way, re-writing history
+		// Insert the block in the canonical way, re-writing history
 		bc.insert(newChain[i])
-		// collect reborn logs due to chain reorg(except head block)
+
+		// Collect reborn logs due to chain reorg (except head block (reverse order))
 		if i != 0 {
 			collectLogs(newChain[i].Hash(), false)
 		}
-		// write lookup entries for hash based transaction/receipt searches
+		// Write lookup entries for hash based transaction/receipt searches
 		rawdb.WriteTxLookupEntries(bc.db, newChain[i])
 		addedTxs = append(addedTxs, newChain[i].Transactions()...)
 	}
-	// calculate the difference between deleted and added transactions
-	diff := types.TxDifference(deletedTxs, addedTxs)
-	// When transactions get deleted from the database that means the
-	// receipts that were created in the fork must also be deleted
+	// When transactions get deleted from the database, the receipts that were
+	// created in the fork must also be deleted
 	batch := bc.db.NewBatch()
-	for _, tx := range diff {
+	for _, tx := range types.TxDifference(deletedTxs, addedTxs) {
 		rawdb.DeleteTxLookupEntry(batch, tx.Hash())
 	}
 	batch.Write()
 
+	// If any logs need to be fired, do it now. In theory we could avoid creating
+	// this goroutine if there are no events to fire, but realistcally that only
+	// ever happens if we're reorging empty blocks, which will only happen on idle
+	// networks where performance is not an issue either way.
+	//
+	// TODO(karalabe): Can we get rid of the goroutine somehow to guarantee correct
+	// event ordering?
+	go func() {
 		if len(deletedLogs) > 0 {
-		go bc.rmLogsFeed.Send(RemovedLogsEvent{deletedLogs})
+			bc.rmLogsFeed.Send(RemovedLogsEvent{deletedLogs})
 		}
 		if len(rebirthLogs) > 0 {
-		go bc.logsFeed.Send(rebirthLogs)
+			bc.logsFeed.Send(rebirthLogs)
 		}
 		if len(oldChain) > 0 {
-		go func() {
 			for _, block := range oldChain {
 				bc.chainSideFeed.Send(ChainSideEvent{Block: block})
 			}
-		}()
 		}
-
+	}()
 	return nil
 }
 

core/blockchain_test.go

@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/ethdb/memorydb"
 	"github.com/ethereum/go-ethereum/params"
 )
 
@@ -916,7 +917,8 @@ func TestLogRebirth(t *testing.T) {
 	var (
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		db      = ethdb.NewMemDatabase()
+		db      = memorydb.New()
+
 		// this code generates a log
 		code     = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
 		gspec    = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{addr1: {Balance: big.NewInt(10000000000000)}}}
@@ -1018,10 +1020,6 @@ func TestLogRebirth(t *testing.T) {
 	if _, err := blockchain.InsertChain(newBlocks); err != nil {
 		t.Fatalf("failed to insert forked chain: %v", err)
 	}
-	// Rebirth logs should omit a newLogEvent
-	if !<-newLogCh {
-		t.Fatalf("failed to receive new log event")
-	}
 	// Ensure removedLog events received
 	select {
 	case ev := <-rmLogsCh:
@@ -1031,13 +1029,18 @@ func TestLogRebirth(t *testing.T) {
 	case <-time.NewTimer(1 * time.Second).C:
 		t.Fatal("Timeout. There is no RemovedLogsEvent has been sent.")
 	}
+	// Rebirth logs should omit a newLogEvent
+	if !<-newLogCh {
+		t.Fatalf("failed to receive new log event")
+	}
 }
 
 func TestSideLogRebirth(t *testing.T) {
 	var (
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		db      = ethdb.NewMemDatabase()
+		db      = memorydb.New()
+
 		// this code generates a log
 		code     = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
 		gspec    = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{addr1: {Balance: big.NewInt(10000000000000)}}}