eth, les: rework chain tracer

eth/api.go

@@ -407,10 +407,11 @@ func (api *DebugAPI) StorageRangeAt(blockHash common.Hash, txIndex int, contract
 	if block == nil {
 		return StorageRangeResult{}, fmt.Errorf("block %#x not found", blockHash)
 	}
-	_, _, statedb, err := api.eth.stateAtTransaction(block, txIndex, 0)
+	_, _, statedb, rel, err := api.eth.stateAtTransaction(block, txIndex, 0)
 	if err != nil {
 		return StorageRangeResult{}, err
 	}
+	defer rel()
 	st := statedb.StorageTrie(contractAddress)
 	if st == nil {
 		return StorageRangeResult{}, fmt.Errorf("account %x doesn't exist", contractAddress)

eth/api_backend.go

@@ -359,10 +359,10 @@ func (b *EthAPIBackend) StartMining(threads int) error {
 	return b.eth.StartMining(threads)
 }
 
-func (b *EthAPIBackend) StateAtBlock(ctx context.Context, block *types.Block, reexec uint64, base *state.StateDB, checkLive, preferDisk bool) (*state.StateDB, error) {
-	return b.eth.StateAtBlock(block, reexec, base, checkLive, preferDisk)
+func (b *EthAPIBackend) StateAtBlock(ctx context.Context, block *types.Block, reexec uint64, base *state.StateDB, readOnly bool) (*state.StateDB, func(), error) {
+	return b.eth.StateAtBlock(block, reexec, base, readOnly)
 }
 
-func (b *EthAPIBackend) StateAtTransaction(ctx context.Context, block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, error) {
+func (b *EthAPIBackend) StateAtTransaction(ctx context.Context, block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, func(), error) {
 	return b.eth.stateAtTransaction(block, txIndex, reexec)
 }

eth/state_accessor.go

@@ -30,73 +30,76 @@ import (
 	"github.com/ethereum/go-ethereum/trie"
 )
 
+// noopReleaser is returned in case there is no operation expected
+// for releasing state.
+var noopReleaser = func() {}
+
 // StateAtBlock retrieves the state database associated with a certain block.
 // If no state is locally available for the given block, a number of blocks
 // are attempted to be reexecuted to generate the desired state. The optional
-// base layer statedb can be passed then it's regarded as the statedb of the
+// base layer statedb can be provided which is regarded as the statedb of the
 // parent block.
+//
+// An additional release function will be returned if the requested state is
+// available. The release is expected be invoked when the state is used, though
+// it can be noop in some cases, otherwise the resources leaking can happen.
+//
 // Parameters:
-// - block: The block for which we want the state (== state at the stateRoot of the parent)
-// - reexec: The maximum number of blocks to reprocess trying to obtain the desired state
-// - base: If the caller is tracing multiple blocks, the caller can provide the parent state
-//         continuously from the callsite.
-// - checklive: if true, then the live 'blockchain' state database is used. If the caller want to
-//        perform Commit or other 'save-to-disk' changes, this should be set to false to avoid
-//        storing trash persistently
-// - preferDisk: this arg can be used by the caller to signal that even though the 'base' is provided,
-//        it would be preferrable to start from a fresh state, if we have it on disk.
-func (eth *Ethereum) StateAtBlock(block *types.Block, reexec uint64, base *state.StateDB, checkLive bool, preferDisk bool) (statedb *state.StateDB, err error) {
+// - block:    The block for which we want the state(state = block.Root)
+// - reexec:   The maximum number of blocks to reprocess trying to obtain the desired state
+// - base:     If the caller is tracing multiple blocks, the caller can provide the parent
+//             state continuously from the callsite.
+// - readOnly: If true, then the live 'blockchain' state database is used. No mutation should
+//             be made from caller, e.g. perform Commit or other 'save-to-disk' changes.
+//             Otherwise, the trash generated by caller may be persisted permanently.
+func (eth *Ethereum) StateAtBlock(block *types.Block, reexec uint64, base *state.StateDB, readOnly bool) (statedb *state.StateDB, rel func(), err error) {
 	var (
 		current  *types.Block
 		database state.Database
 		report   = true
 		origin   = block.NumberU64()
 	)
-	// Check the live database first if we have the state fully available, use that.
-	if checkLive {
-		statedb, err = eth.blockchain.StateAt(block.Root())
-		if err == nil {
-			return statedb, nil
+	// The state is only for reading purposes, check the state presence in
+	// live database.
+	if readOnly {
+		// The state is available in live database, create a reference
+		// on top to prevent garbage collection and return a release
+		// function to deref it.
+		if statedb, err = eth.blockchain.StateAt(block.Root()); err == nil {
+			statedb.Database().TrieDB().Reference(block.Root(), common.Hash{})
+			return statedb, func() { statedb.Database().TrieDB().Dereference(block.Root()) }, nil
 		}
 	}
+	// The state is both for reading and writing, construct an ephemeral
+	// trie.Database for isolating the live one and check the state presence.
+	database = state.NewDatabaseWithConfig(eth.chainDb, &trie.Config{Cache: 16})
+
+	// If the requested state is available in disk, return it with noop
+	// release function. It's also beneficial to switch to disk state with
+	// a fresh created ephemeral trie database when tracing multiple blocks
+	// to avoid caching too many junks in memory.
+	statedb, err = state.New(current.Root(), database, nil)
+	if err == nil {
+		return statedb, noopReleaser, nil
+	}
+	// The state is not available in disk, try to recover it. The state will
+	// be constructed on the ephemeral trie database.
 	if base != nil {
-		if preferDisk {
-			// Create an ephemeral trie.Database for isolating the live one. Otherwise
-			// the internal junks created by tracing will be persisted into the disk.
-			database = state.NewDatabaseWithConfig(eth.chainDb, &trie.Config{Cache: 16})
-			if statedb, err = state.New(block.Root(), database, nil); err == nil {
-				log.Info("Found disk backend for state trie", "root", block.Root(), "number", block.Number())
-				return statedb, nil
-			}
-		}
 		// The optional base statedb is given, mark the start point as parent block
 		statedb, database, report = base, base.Database(), false
 		current = eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
 	} else {
-		// Otherwise try to reexec blocks until we find a state or reach our limit
+		// Otherwise, try to reexec blocks until we find a state or reach our limit
 		current = block
 
-		// Create an ephemeral trie.Database for isolating the live one. Otherwise
-		// the internal junks created by tracing will be persisted into the disk.
-		database = state.NewDatabaseWithConfig(eth.chainDb, &trie.Config{Cache: 16})
-
-		// If we didn't check the dirty database, do check the clean one, otherwise
-		// we would rewind past a persisted block (specific corner case is chain
-		// tracing from the genesis).
-		if !checkLive {
-			statedb, err = state.New(current.Root(), database, nil)
-			if err == nil {
-				return statedb, nil
-			}
-		}
 		// Database does not have the state for the given block, try to regenerate
 		for i := uint64(0); i < reexec; i++ {
 			if current.NumberU64() == 0 {
-				return nil, errors.New("genesis state is missing")
+				return nil, nil, errors.New("genesis state is missing")
 			}
 			parent := eth.blockchain.GetBlock(current.ParentHash(), current.NumberU64()-1)
 			if parent == nil {
-				return nil, fmt.Errorf("missing block %v %d", current.ParentHash(), current.NumberU64()-1)
+				return nil, nil, fmt.Errorf("missing block %v %d", current.ParentHash(), current.NumberU64()-1)
 			}
 			current = parent
 
@@ -108,13 +111,14 @@ func (eth *Ethereum) StateAtBlock(block *types.Block, reexec uint64, base *state
 		if err != nil {
 			switch err.(type) {
 			case *trie.MissingNodeError:
-				return nil, fmt.Errorf("required historical state unavailable (reexec=%d)", reexec)
+				return nil, nil, fmt.Errorf("required historical state unavailable (reexec=%d)", reexec)
 			default:
-				return nil, err
+				return nil, nil, err
 			}
 		}
 	}
-	// State was available at historical point, regenerate
+	// State is available at historical point, re-execute the blocks on top for
+	// the desired state.
 	var (
 		start  = time.Now()
 		logged time.Time
@@ -129,22 +133,24 @@ func (eth *Ethereum) StateAtBlock(block *types.Block, reexec uint64, base *state
 		// Retrieve the next block to regenerate and process it
 		next := current.NumberU64() + 1
 		if current = eth.blockchain.GetBlockByNumber(next); current == nil {
-			return nil, fmt.Errorf("block #%d not found", next)
+			return nil, nil, fmt.Errorf("block #%d not found", next)
 		}
 		_, _, _, err := eth.blockchain.Processor().Process(current, statedb, vm.Config{})
 		if err != nil {
-			return nil, fmt.Errorf("processing block %d failed: %v", current.NumberU64(), err)
+			return nil, nil, fmt.Errorf("processing block %d failed: %v", current.NumberU64(), err)
 		}
 		// Finalize the state so any modifications are written to the trie
 		root, err := statedb.Commit(eth.blockchain.Config().IsEIP158(current.Number()))
 		if err != nil {
-			return nil, fmt.Errorf("stateAtBlock commit failed, number %d root %v: %w",
+			return nil, nil, fmt.Errorf("stateAtBlock commit failed, number %d root %v: %w",
 				current.NumberU64(), current.Root().Hex(), err)
 		}
 		statedb, err = state.New(root, database, nil)
 		if err != nil {
-			return nil, fmt.Errorf("state reset after block %d failed: %v", current.NumberU64(), err)
+			return nil, nil, fmt.Errorf("state reset after block %d failed: %v", current.NumberU64(), err)
 		}
+		// Hold the state reference and also drop the parent state
+		// to prevent accumulating too many nodes in memory.
 		database.TrieDB().Reference(root, common.Hash{})
 		if parent != (common.Hash{}) {
 			database.TrieDB().Dereference(parent)
@@ -155,28 +161,28 @@ func (eth *Ethereum) StateAtBlock(block *types.Block, reexec uint64, base *state
 		nodes, imgs := database.TrieDB().Size()
 		log.Info("Historical state regenerated", "block", current.NumberU64(), "elapsed", time.Since(start), "nodes", nodes, "preimages", imgs)
 	}
-	return statedb, nil
+	return statedb, func() { database.TrieDB().Dereference(block.Root()) }, nil
 }
 
 // stateAtTransaction returns the execution environment of a certain transaction.
-func (eth *Ethereum) stateAtTransaction(block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, error) {
+func (eth *Ethereum) stateAtTransaction(block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, func(), error) {
 	// Short circuit if it's genesis block.
 	if block.NumberU64() == 0 {
-		return nil, vm.BlockContext{}, nil, errors.New("no transaction in genesis")
+		return nil, vm.BlockContext{}, nil, nil, errors.New("no transaction in genesis")
 	}
 	// Create the parent state database
 	parent := eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
 	if parent == nil {
-		return nil, vm.BlockContext{}, nil, fmt.Errorf("parent %#x not found", block.ParentHash())
+		return nil, vm.BlockContext{}, nil, nil, fmt.Errorf("parent %#x not found", block.ParentHash())
 	}
 	// Lookup the statedb of parent block from the live database,
 	// otherwise regenerate it on the flight.
-	statedb, err := eth.StateAtBlock(parent, reexec, nil, true, false)
+	statedb, rel, err := eth.StateAtBlock(parent, reexec, nil, true)
 	if err != nil {
-		return nil, vm.BlockContext{}, nil, err
+		return nil, vm.BlockContext{}, nil, nil, err
 	}
 	if txIndex == 0 && len(block.Transactions()) == 0 {
-		return nil, vm.BlockContext{}, statedb, nil
+		return nil, vm.BlockContext{}, statedb, rel, nil
 	}
 	// Recompute transactions up to the target index.
 	signer := types.MakeSigner(eth.blockchain.Config(), block.Number())
@@ -186,17 +192,17 @@ func (eth *Ethereum) stateAtTransaction(block *types.Block, txIndex int, reexec
 		txContext := core.NewEVMTxContext(msg)
 		context := core.NewEVMBlockContext(block.Header(), eth.blockchain, nil)
 		if idx == txIndex {
-			return msg, context, statedb, nil
+			return msg, context, statedb, rel, nil
 		}
 		// Not yet the searched for transaction, execute on top of the current state
 		vmenv := vm.NewEVM(context, txContext, statedb, eth.blockchain.Config(), vm.Config{})
 		statedb.Prepare(tx.Hash(), idx)
 		if _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(tx.Gas())); err != nil {
-			return nil, vm.BlockContext{}, nil, fmt.Errorf("transaction %#x failed: %v", tx.Hash(), err)
+			return nil, vm.BlockContext{}, nil, nil, fmt.Errorf("transaction %#x failed: %v", tx.Hash(), err)
 		}
 		// Ensure any modifications are committed to the state
 		// Only delete empty objects if EIP158/161 (a.k.a Spurious Dragon) is in effect
 		statedb.Finalise(vmenv.ChainConfig().IsEIP158(block.Number()))
 	}
-	return nil, vm.BlockContext{}, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, block.Hash())
+	return nil, vm.BlockContext{}, nil, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, block.Hash())
 }