core: added a new RemovedLogEvent

When a chain reorganisation occurs we collect the logs that were deleted
during the chain reorganisation. The removed logs are posted to the
event mux indicating that those were deleted during the reorg.

4 files changed, 68 insertions, 4 deletions

diff --git a/core/blockchain.go b/core/blockchain.go
index 5a6795b3e..dc6e0835c 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -1240,6 +1240,17 @@ func (self *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 		oldStart    = oldBlock
 		newStart    = newBlock
 		deletedTxs  types.Transactions
+		deletedLogs vm.Logs
+		// 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.
+		collectLogs = func(h common.Hash) {
+			// Coalesce logs
+			receipts := GetBlockReceipts(self.chainDb, h)
+			for _, receipt := range receipts {
+				deletedLogs = append(deletedLogs, receipt.Logs...)
+			}
+		}
 	)
 
 	// first reduce whoever is higher bound
@@ -1247,6 +1258,8 @@ func (self *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 		// reduce old chain
 		for oldBlock = oldBlock; oldBlock != nil && oldBlock.NumberU64() != newBlock.NumberU64(); oldBlock = self.GetBlock(oldBlock.ParentHash()) {
 			deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
+
+			collectLogs(oldBlock.Hash())
 		}
 	} else {
 		// reduce new chain and append new chain blocks for inserting later on
@@ -1269,6 +1282,7 @@ func (self *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 		}
 		newChain = append(newChain, newBlock)
 		deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
+		collectLogs(oldBlock.Hash())
 
 		oldBlock, newBlock = self.GetBlock(oldBlock.ParentHash()), self.GetBlock(newBlock.ParentHash())
 		if oldBlock == nil {
@@ -1302,7 +1316,6 @@ func (self *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 		if err := WriteMipmapBloom(self.chainDb, block.NumberU64(), receipts); err != nil {
 			return err
 		}
-
 		addedTxs = append(addedTxs, block.Transactions()...)
 	}
 
@@ -1316,7 +1329,12 @@ func (self *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 	}
 	// Must be posted in a goroutine because of the transaction pool trying
 	// to acquire the chain manager lock
-	go self.eventMux.Post(RemovedTransactionEvent{diff})
+	if len(diff) > 0 {
+		go self.eventMux.Post(RemovedTransactionEvent{diff})
+	}
+	if len(deletedLogs) > 0 {
+		go self.eventMux.Post(RemovedLogEvent{deletedLogs})
+	}
 
 	return nil
 }
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index 6e1c5fdc7..b4ac1696a 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -963,3 +963,46 @@ func TestChainTxReorgs(t *testing.T) {
 		}
 	}
 }
+
+func TestLogReorgs(t *testing.T) {
+	params.MinGasLimit = big.NewInt(125000)      // Minimum the gas limit may ever be.
+	params.GenesisGasLimit = big.NewInt(3141592) // Gas limit of the Genesis block.
+
+	var (
+		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
+		db, _   = ethdb.NewMemDatabase()
+		// this code generates a log
+		code = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
+	)
+	genesis := WriteGenesisBlockForTesting(db,
+		GenesisAccount{addr1, big.NewInt(10000000000000)},
+	)
+
+	evmux := &event.TypeMux{}
+	blockchain, _ := NewBlockChain(db, FakePow{}, evmux)
+
+	subs := evmux.Subscribe(RemovedLogEvent{})
+	chain, _ := GenerateChain(genesis, db, 2, func(i int, gen *BlockGen) {
+		if i == 1 {
+			tx, err := types.NewContractCreation(gen.TxNonce(addr1), new(big.Int), big.NewInt(1000000), new(big.Int), code).SignECDSA(key1)
+			if err != nil {
+				t.Fatalf("failed to create tx: %v", err)
+			}
+			gen.AddTx(tx)
+		}
+	})
+	if _, err := blockchain.InsertChain(chain); err != nil {
+		t.Fatalf("failed to insert chain: %v", err)
+	}
+
+	chain, _ = GenerateChain(genesis, db, 3, func(i int, gen *BlockGen) {})
+	if _, err := blockchain.InsertChain(chain); err != nil {
+		t.Fatalf("failed to insert forked chain: %v", err)
+	}
+
+	ev := <-subs.Chan()
+	if len(ev.Data.(RemovedLogEvent).Logs) == 0 {
+		t.Error("expected logs")
+	}
+}
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 6d3152d97..4f6fa3989 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -90,6 +90,7 @@ func (b *BlockGen) AddTx(tx *types.Transaction) {
 	if b.gasPool == nil {
 		b.SetCoinbase(common.Address{})
 	}
+	b.statedb.StartRecord(tx.Hash(), common.Hash{}, len(b.txs))
 	_, gas, err := ApplyMessage(NewEnv(b.statedb, nil, tx, b.header), tx, b.gasPool)
 	if err != nil {
 		panic(err)
@@ -97,8 +98,7 @@ func (b *BlockGen) AddTx(tx *types.Transaction) {
 	root := b.statedb.IntermediateRoot()
 	b.header.GasUsed.Add(b.header.GasUsed, gas)
 	receipt := types.NewReceipt(root.Bytes(), b.header.GasUsed)
-	logs := b.statedb.GetLogs(tx.Hash())
-	receipt.Logs = logs
+	receipt.Logs = b.statedb.GetLogs(tx.Hash())
 	receipt.Bloom = types.CreateBloom(types.Receipts{receipt})
 	b.txs = append(b.txs, tx)
 	b.receipts = append(b.receipts, receipt)
diff --git a/core/events.go b/core/events.go
index 8cf230dda..1a760c71c 100644
--- a/core/events.go
+++ b/core/events.go
@@ -39,6 +39,9 @@ type NewMinedBlockEvent struct{ Block *types.Block }
 // RemovedTransactionEvent is posted when a reorg happens
 type RemovedTransactionEvent struct{ Txs types.Transactions }
 
+// RemovedLogEvent is posted when a reorg happens
+type RemovedLogEvent struct{ Logs vm.Logs }
+
 // ChainSplit is posted when a new head is detected
 type ChainSplitEvent struct {
 	Block *types.Block