eth/tracers: move tracing APIs into eth/tracers (#22161)

This moves the tracing RPC API implementation to package eth/tracers.
By doing so, package eth no longer depends on tracing and the duktape JS engine.

The change also enables tracing using the light client. All tracing methods work with the
light client, but it's a lot slower compared to using a full node.

cmd/utils/flags.go

@@ -45,6 +45,7 @@ import (
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/eth/downloader"
 	"github.com/ethereum/go-ethereum/eth/gasprice"
+	"github.com/ethereum/go-ethereum/eth/tracers"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/ethstats"
 	"github.com/ethereum/go-ethereum/graphql"
@@ -1724,6 +1725,7 @@ func RegisterEthService(stack *node.Node, cfg *eth.Config) ethapi.Backend {
 		if err != nil {
 			Fatalf("Failed to register the Ethereum service: %v", err)
 		}
+		stack.RegisterAPIs(tracers.APIs(backend.ApiBackend))
 		return backend.ApiBackend
 	}
 	backend, err := eth.New(stack, cfg)
@@ -1736,6 +1738,7 @@ func RegisterEthService(stack *node.Node, cfg *eth.Config) ethapi.Backend {
 			Fatalf("Failed to create the LES server: %v", err)
 		}
 	}
+	stack.RegisterAPIs(tracers.APIs(backend.APIBackend))
 	return backend.APIBackend
 }
 

eth/api.go

@@ -426,10 +426,11 @@ func (api *PrivateDebugAPI) StorageRangeAt(blockHash common.Hash, txIndex int, c
 	if block == nil {
 		return StorageRangeResult{}, fmt.Errorf("block %#x not found", blockHash)
 	}
-	_, _, statedb, err := api.computeTxEnv(block, txIndex, 0)
+	_, _, statedb, release, err := api.eth.stateAtTransaction(block, txIndex, 0)
 	if err != nil {
 		return StorageRangeResult{}, err
 	}
+	defer release()
 	st := statedb.StorageTrie(contractAddress)
 	if st == nil {
 		return StorageRangeResult{}, fmt.Errorf("account %x doesn't exist", contractAddress)

eth/api_backend.go

@@ -326,3 +326,15 @@ func (b *EthAPIBackend) Miner() *miner.Miner {
 func (b *EthAPIBackend) StartMining(threads int) error {
 	return b.eth.StartMining(threads)
 }
+
+func (b *EthAPIBackend) StateAtBlock(ctx context.Context, block *types.Block, reexec uint64) (*state.StateDB, func(), error) {
+	return b.eth.stateAtBlock(block, reexec)
+}
+
+func (b *EthAPIBackend) StatesInRange(ctx context.Context, fromBlock *types.Block, toBlock *types.Block, reexec uint64) ([]*state.StateDB, func(), error) {
+	return b.eth.statesInRange(fromBlock, toBlock, reexec)
+}
+
+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

@@ -0,0 +1,230 @@
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package eth
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+// 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.
+func (eth *Ethereum) stateAtBlock(block *types.Block, reexec uint64) (statedb *state.StateDB, release func(), err error) {
+	// If we have the state fully available, use that
+	statedb, err = eth.blockchain.StateAt(block.Root())
+	if err == nil {
+		return statedb, func() {}, nil
+	}
+	// Otherwise try to reexec blocks until we find a state or reach our limit
+	origin := block.NumberU64()
+	database := state.NewDatabaseWithConfig(eth.chainDb, &trie.Config{Cache: 16, Preimages: true})
+
+	for i := uint64(0); i < reexec; i++ {
+		if block.NumberU64() == 0 {
+			return nil, nil, errors.New("genesis state is missing")
+		}
+		parent := eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
+		if parent == nil {
+			return nil, nil, fmt.Errorf("missing block %v %d", block.ParentHash(), block.NumberU64()-1)
+		}
+		block = parent
+
+		statedb, err = state.New(block.Root(), database, nil)
+		if err == nil {
+			break
+		}
+	}
+	if err != nil {
+		switch err.(type) {
+		case *trie.MissingNodeError:
+			return nil, nil, fmt.Errorf("required historical state unavailable (reexec=%d)", reexec)
+		default:
+			return nil, nil, err
+		}
+	}
+	// State was available at historical point, regenerate
+	var (
+		start  = time.Now()
+		logged time.Time
+		parent common.Hash
+	)
+	defer func() {
+		if err != nil && parent != (common.Hash{}) {
+			database.TrieDB().Dereference(parent)
+		}
+	}()
+	for block.NumberU64() < origin {
+		// Print progress logs if long enough time elapsed
+		if time.Since(logged) > 8*time.Second {
+			log.Info("Regenerating historical state", "block", block.NumberU64()+1, "target", origin, "remaining", origin-block.NumberU64()-1, "elapsed", time.Since(start))
+			logged = time.Now()
+		}
+		// Retrieve the next block to regenerate and process it
+		if block = eth.blockchain.GetBlockByNumber(block.NumberU64() + 1); block == nil {
+			return nil, nil, fmt.Errorf("block #%d not found", block.NumberU64()+1)
+		}
+		_, _, _, err := eth.blockchain.Processor().Process(block, statedb, vm.Config{})
+		if err != nil {
+			return nil, nil, fmt.Errorf("processing block %d failed: %v", block.NumberU64(), err)
+		}
+		// Finalize the state so any modifications are written to the trie
+		root, err := statedb.Commit(eth.blockchain.Config().IsEIP158(block.Number()))
+		if err != nil {
+			return nil, nil, err
+		}
+		statedb, err = state.New(root, database, nil)
+		if err != nil {
+			return nil, nil, fmt.Errorf("state reset after block %d failed: %v", block.NumberU64(), err)
+		}
+		database.TrieDB().Reference(root, common.Hash{})
+		if parent != (common.Hash{}) {
+			database.TrieDB().Dereference(parent)
+		}
+		parent = root
+	}
+	nodes, imgs := database.TrieDB().Size()
+	log.Info("Historical state regenerated", "block", block.NumberU64(), "elapsed", time.Since(start), "nodes", nodes, "preimages", imgs)
+	return statedb, func() { database.TrieDB().Dereference(parent) }, nil
+}
+
+// statesInRange retrieves a batch of state databases associated with the specific
+// block ranges. If no state is locally available for the given range, a number of
+// blocks are attempted to be reexecuted to generate the ancestor state.
+func (eth *Ethereum) statesInRange(fromBlock, toBlock *types.Block, reexec uint64) (states []*state.StateDB, release func(), err error) {
+	statedb, err := eth.blockchain.StateAt(fromBlock.Root())
+	if err != nil {
+		statedb, _, err = eth.stateAtBlock(fromBlock, reexec)
+	}
+	if err != nil {
+		return nil, nil, err
+	}
+	states = append(states, statedb.Copy())
+
+	var (
+		logged   time.Time
+		parent   common.Hash
+		start    = time.Now()
+		refs     = []common.Hash{fromBlock.Root()}
+		database = state.NewDatabaseWithConfig(eth.chainDb, &trie.Config{Cache: 16, Preimages: true})
+	)
+	// Release all resources(including the states referenced by `stateAtBlock`)
+	// if error is returned.
+	defer func() {
+		if err != nil {
+			for _, ref := range refs {
+				database.TrieDB().Dereference(ref)
+			}
+		}
+	}()
+	for i := fromBlock.NumberU64() + 1; i <= toBlock.NumberU64(); i++ {
+		// Print progress logs if long enough time elapsed
+		if time.Since(logged) > 8*time.Second {
+			logged = time.Now()
+			log.Info("Regenerating historical state", "block", i, "target", fromBlock.NumberU64(), "remaining", toBlock.NumberU64()-i, "elapsed", time.Since(start))
+		}
+		// Retrieve the next block to regenerate and process it
+		block := eth.blockchain.GetBlockByNumber(i)
+		if block == nil {
+			return nil, nil, fmt.Errorf("block #%d not found", i)
+		}
+		_, _, _, err := eth.blockchain.Processor().Process(block, statedb, vm.Config{})
+		if err != nil {
+			return nil, nil, fmt.Errorf("processing block %d failed: %v", block.NumberU64(), err)
+		}
+		// Finalize the state so any modifications are written to the trie
+		root, err := statedb.Commit(eth.blockchain.Config().IsEIP158(block.Number()))
+		if err != nil {
+			return nil, nil, err
+		}
+		statedb, err := eth.blockchain.StateAt(root)
+		if err != nil {
+			return nil, nil, fmt.Errorf("state reset after block %d failed: %v", block.NumberU64(), err)
+		}
+		states = append(states, statedb.Copy())
+
+		// Reference the trie twice, once for us, once for the tracer
+		database.TrieDB().Reference(root, common.Hash{})
+		database.TrieDB().Reference(root, common.Hash{})
+		refs = append(refs, root)
+
+		// Dereference all past tries we ourselves are done working with
+		if parent != (common.Hash{}) {
+			database.TrieDB().Dereference(parent)
+		}
+		parent = root
+	}
+	// release is handler to release all states referenced, including
+	// the one referenced in `stateAtBlock`.
+	release = func() {
+		for _, ref := range refs {
+			database.TrieDB().Dereference(ref)
+		}
+	}
+	return states, release, 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, func(), error) {
+	// Short circuit if it's genesis block.
+	if block.NumberU64() == 0 {
+		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, nil, fmt.Errorf("parent %#x not found", block.ParentHash())
+	}
+	statedb, release, err := eth.stateAtBlock(parent, reexec)
+	if err != nil {
+		return nil, vm.BlockContext{}, nil, nil, err
+	}
+	if txIndex == 0 && len(block.Transactions()) == 0 {
+		return nil, vm.BlockContext{}, statedb, release, nil
+	}
+	// Recompute transactions up to the target index.
+	signer := types.MakeSigner(eth.blockchain.Config(), block.Number())
+	for idx, tx := range block.Transactions() {
+		// Assemble the transaction call message and return if the requested offset
+		msg, _ := tx.AsMessage(signer)
+		txContext := core.NewEVMTxContext(msg)
+		context := core.NewEVMBlockContext(block.Header(), eth.blockchain, nil)
+		if idx == txIndex {
+			return msg, context, statedb, release, 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{})
+		if _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(tx.Gas())); err != nil {
+			release()
+			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()))
+	}
+	release()
+	return nil, vm.BlockContext{}, nil, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, block.Hash())
+}

eth/api_tracer.go → eth/tracers/api.go

@@ -1,4 +1,4 @@
-// Copyright 2017 The go-ethereum Authors
+// Copyright 2021 The go-ethereum Authors
 // This file is part of the go-ethereum library.
 //
 // The go-ethereum library is free software: you can redistribute it and/or modify
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package eth
+package tracers
 
 import (
 	"bufio"
@@ -30,18 +30,18 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
-	"github.com/ethereum/go-ethereum/eth/tracers"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/rpc"
-	"github.com/ethereum/go-ethereum/trie"
 )
 
 const (
@@ -55,6 +55,105 @@ const (
 	defaultTraceReexec = uint64(128)
 )
 
+// Backend interface provides the common API services (that are provided by
+// both full and light clients) with access to necessary functions.
+type Backend interface {
+	HeaderByHash(ctx context.Context, hash common.Hash) (*types.Header, error)
+	HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error)
+	BlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error)
+	BlockByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Block, error)
+	GetTransaction(ctx context.Context, txHash common.Hash) (*types.Transaction, common.Hash, uint64, uint64, error)
+	RPCGasCap() uint64
+	ChainConfig() *params.ChainConfig
+	Engine() consensus.Engine
+	ChainDb() ethdb.Database
+	StateAtBlock(ctx context.Context, block *types.Block, reexec uint64) (*state.StateDB, func(), error)
+	StateAtTransaction(ctx context.Context, block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, func(), error)
+	StatesInRange(ctx context.Context, fromBlock *types.Block, toBlock *types.Block, reexec uint64) ([]*state.StateDB, func(), error)
+}
+
+// API is the collection of tracing APIs exposed over the private debugging endpoint.
+type API struct {
+	backend Backend
+}
+
+// NewAPI creates a new API definition for the tracing methods of the Ethereum service.
+func NewAPI(backend Backend) *API {
+	return &API{backend: backend}
+}
+
+type chainContext struct {
+	api *API
+	ctx context.Context
+}
+
+func (context *chainContext) Engine() consensus.Engine {
+	return context.api.backend.Engine()
+}
+
+func (context *chainContext) GetHeader(hash common.Hash, number uint64) *types.Header {
+	header, err := context.api.backend.HeaderByNumber(context.ctx, rpc.BlockNumber(number))
+	if err != nil {
+		return nil
+	}
+	if header.Hash() == hash {
+		return header
+	}
+	header, err = context.api.backend.HeaderByHash(context.ctx, hash)
+	if err != nil {
+		return nil
+	}
+	return header
+}
+
+// chainContext construts the context reader which is used by the evm for reading
+// the necessary chain context.
+func (api *API) chainContext(ctx context.Context) core.ChainContext {
+	return &chainContext{api: api, ctx: ctx}
+}
+
+// blockByNumber is the wrapper of the chain access function offered by the backend.
+// It will return an error if the block is not found.
+func (api *API) blockByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Block, error) {
+	block, err := api.backend.BlockByNumber(ctx, number)
+	if err != nil {
+		return nil, err
+	}
+	if block == nil {
+		return nil, fmt.Errorf("block #%d not found", number)
+	}
+	return block, nil
+}
+
+// blockByHash is the wrapper of the chain access function offered by the backend.
+// It will return an error if the block is not found.
+func (api *API) blockByHash(ctx context.Context, hash common.Hash) (*types.Block, error) {
+	block, err := api.backend.BlockByHash(ctx, hash)
+	if err != nil {
+		return nil, err
+	}
+	if block == nil {
+		return nil, fmt.Errorf("block %s not found", hash.Hex())
+	}
+	return block, nil
+}
+
+// blockByNumberAndHash is the wrapper of the chain access function offered by
+// the backend. It will return an error if the block is not found.
+//
+// Note this function is friendly for the light client which can only retrieve the
+// historical(before the CHT) header/block by number.
+func (api *API) blockByNumberAndHash(ctx context.Context, number rpc.BlockNumber, hash common.Hash) (*types.Block, error) {
+	block, err := api.blockByNumber(ctx, number)
+	if err != nil {
+		return nil, err
+	}
+	if block.Hash() == hash {
+		return block, nil
+	}
+	return api.blockByHash(ctx, hash)
+}
+
 // TraceConfig holds extra parameters to trace functions.
 type TraceConfig struct {
 	*vm.LogConfig
@@ -81,7 +180,6 @@ type txTraceResult struct {
 type blockTraceTask struct {
 	statedb *state.StateDB   // Intermediate state prepped for tracing
 	block   *types.Block     // Block to trace the transactions from
-	rootref common.Hash      // Trie root reference held for this task
 	results []*txTraceResult // Trace results procudes by the task
 }
 
@@ -102,32 +200,14 @@ type txTraceTask struct {
 
 // TraceChain returns the structured logs created during the execution of EVM
 // between two blocks (excluding start) and returns them as a JSON object.
-func (api *PrivateDebugAPI) TraceChain(ctx context.Context, start, end rpc.BlockNumber, config *TraceConfig) (*rpc.Subscription, error) {
-	// Fetch the block interval that we want to trace
-	var from, to *types.Block
-
-	switch start {
-	case rpc.PendingBlockNumber:
-		from = api.eth.miner.PendingBlock()
-	case rpc.LatestBlockNumber:
-		from = api.eth.blockchain.CurrentBlock()
-	default:
-		from = api.eth.blockchain.GetBlockByNumber(uint64(start))
-	}
-	switch end {
-	case rpc.PendingBlockNumber:
-		to = api.eth.miner.PendingBlock()
-	case rpc.LatestBlockNumber:
-		to = api.eth.blockchain.CurrentBlock()
-	default:
-		to = api.eth.blockchain.GetBlockByNumber(uint64(end))
-	}
-	// Trace the chain if we've found all our blocks
-	if from == nil {
-		return nil, fmt.Errorf("starting block #%d not found", start)
+func (api *API) TraceChain(ctx context.Context, start, end rpc.BlockNumber, config *TraceConfig) (*rpc.Subscription, error) { // Fetch the block interval that we want to trace
+	from, err := api.blockByNumber(ctx, start)
+	if err != nil {
+		return nil, err
 	}
-	if to == nil {
-		return nil, fmt.Errorf("end block #%d not found", end)
+	to, err := api.blockByNumber(ctx, end)
+	if err != nil {
+		return nil, err
 	}
 	if from.Number().Cmp(to.Number()) >= 0 {
 		return nil, fmt.Errorf("end block (#%d) needs to come after start block (#%d)", end, start)
@@ -138,7 +218,7 @@ func (api *PrivateDebugAPI) TraceChain(ctx context.Context, start, end rpc.Block
 // traceChain configures a new tracer according to the provided configuration, and
 // executes all the transactions contained within. The return value will be one item
 // per transaction, dependent on the requested tracer.
-func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Block, config *TraceConfig) (*rpc.Subscription, error) {
+func (api *API) traceChain(ctx context.Context, start, end *types.Block, config *TraceConfig) (*rpc.Subscription, error) {
 	// Tracing a chain is a **long** operation, only do with subscriptions
 	notifier, supported := rpc.NotifierFromContext(ctx)
 	if !supported {
@@ -146,46 +226,25 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 	}
 	sub := notifier.CreateSubscription()
 
-	// Ensure we have a valid starting state before doing any work
-	origin := start.NumberU64()
-	database := state.NewDatabaseWithConfig(api.eth.ChainDb(), &trie.Config{Cache: 16, Preimages: true})
-
-	if number := start.NumberU64(); number > 0 {
-		start = api.eth.blockchain.GetBlock(start.ParentHash(), start.NumberU64()-1)
-		if start == nil {
-			return nil, fmt.Errorf("parent block #%d not found", number-1)
-		}
+	// Shift the border to a block ahead in order to get the states
+	// before these blocks.
+	endBlock, err := api.blockByNumberAndHash(ctx, rpc.BlockNumber(end.NumberU64()-1), end.ParentHash())
+	if err != nil {
+		return nil, err
+	}
+	// Prepare all the states for tracing. Note this procedure can take very
+	// long time. Timeout mechanism is necessary.
+	reexec := defaultTraceReexec
+	if config != nil && config.Reexec != nil {
+		reexec = *config.Reexec
 	}
-	statedb, err := state.New(start.Root(), database, nil)
+	states, release, err := api.backend.StatesInRange(ctx, start, endBlock, reexec)
 	if err != nil {
-		// If the starting state is missing, allow some number of blocks to be reexecuted
-		reexec := defaultTraceReexec
-		if config != nil && config.Reexec != nil {
-			reexec = *config.Reexec
-		}
-		// Find the most recent block that has the state available
-		for i := uint64(0); i < reexec; i++ {
-			start = api.eth.blockchain.GetBlock(start.ParentHash(), start.NumberU64()-1)
-			if start == nil {
-				break
-			}
-			if statedb, err = state.New(start.Root(), database, nil); err == nil {
-				break
-			}
-		}
-		// If we still don't have the state available, bail out
-		if err != nil {
-			switch err.(type) {
-			case *trie.MissingNodeError:
-				return nil, errors.New("required historical state unavailable")
-			default:
-				return nil, err
-			}
-		}
+		return nil, err
 	}
-	// Execute all the transaction contained within the chain concurrently for each block
-	blocks := int(end.NumberU64() - origin)
+	defer release() // Release all the resources in the last step.
 
+	blocks := int(end.NumberU64() - start.NumberU64())
 	threads := runtime.NumCPU()
 	if threads > blocks {
 		threads = blocks
@@ -202,8 +261,8 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 
 			// Fetch and execute the next block trace tasks
 			for task := range tasks {
-				signer := types.MakeSigner(api.eth.blockchain.Config(), task.block.Number())
-				blockCtx := core.NewEVMBlockContext(task.block.Header(), api.eth.blockchain, nil)
+				signer := types.MakeSigner(api.backend.ChainConfig(), task.block.Number())
+				blockCtx := core.NewEVMBlockContext(task.block.Header(), api.chainContext(ctx), nil)
 				// Trace all the transactions contained within
 				for i, tx := range task.block.Transactions() {
 					msg, _ := tx.AsMessage(signer)
@@ -214,7 +273,7 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 						break
 					}
 					// Only delete empty objects if EIP158/161 (a.k.a Spurious Dragon) is in effect
-					task.statedb.Finalise(api.eth.blockchain.Config().IsEIP158(task.block.Number()))
+					task.statedb.Finalise(api.backend.ChainConfig().IsEIP158(task.block.Number()))
 					task.results[i] = &txTraceResult{Result: res}
 				}
 				// Stream the result back to the user or abort on teardown
@@ -235,7 +294,6 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 			number uint64
 			traced uint64
 			failed error
-			proot  common.Hash
 		)
 		// Ensure everything is properly cleaned up on any exit path
 		defer func() {
@@ -262,60 +320,23 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 			}
 			// Print progress logs if long enough time elapsed
 			if time.Since(logged) > 8*time.Second {
-				if number > origin {
-					nodes, imgs := database.TrieDB().Size()
-					log.Info("Tracing chain segment", "start", origin, "end", end.NumberU64(), "current", number, "transactions", traced, "elapsed", time.Since(begin), "memory", nodes+imgs)
-				} else {
-					log.Info("Preparing state for chain trace", "block", number, "start", origin, "elapsed", time.Since(begin))
-				}
 				logged = time.Now()
+				log.Info("Tracing chain segment", "start", start.NumberU64(), "end", end.NumberU64(), "current", number, "transactions", traced, "elapsed", time.Since(begin))
 			}
 			// Retrieve the next block to trace
-			block := api.eth.blockchain.GetBlockByNumber(number)
-			if block == nil {
-				failed = fmt.Errorf("block #%d not found", number)
-				break
-			}
-			// Send the block over to the concurrent tracers (if not in the fast-forward phase)
-			if number > origin {
-				txs := block.Transactions()
-
-				select {
-				case tasks <- &blockTraceTask{statedb: statedb.Copy(), block: block, rootref: proot, results: make([]*txTraceResult, len(txs))}:
-				case <-notifier.Closed():
-					return
-				}
-				traced += uint64(len(txs))
-			}
-			// Generate the next state snapshot fast without tracing
-			_, _, _, err := api.eth.blockchain.Processor().Process(block, statedb, vm.Config{})
+			block, err := api.blockByNumber(ctx, rpc.BlockNumber(number))
 			if err != nil {
 				failed = err
 				break
 			}
-			// Finalize the state so any modifications are written to the trie
-			root, err := statedb.Commit(api.eth.blockchain.Config().IsEIP158(block.Number()))
-			if err != nil {
-				failed = err
-				break
-			}
-			statedb, err = state.New(root, database, nil)
-			if err != nil {
-				failed = err
-				break
-			}
-			// Reference the trie twice, once for us, once for the tracer
-			database.TrieDB().Reference(root, common.Hash{})
-			if number >= origin {
-				database.TrieDB().Reference(root, common.Hash{})
-			}
-			// Dereference all past tries we ourselves are done working with
-			if proot != (common.Hash{}) {
-				database.TrieDB().Dereference(proot)
+			// Send the block over to the concurrent tracers (if not in the fast-forward phase)
+			txs := block.Transactions()
+			select {
+			case tasks <- &blockTraceTask{statedb: states[int(number-start.NumberU64()-1)], block: block, results: make([]*txTraceResult, len(txs))}:
+			case <-notifier.Closed():
+				return
 			}
-			proot = root
-
-			// TODO(karalabe): Do we need the preimages? Won't they accumulate too much?
+			traced += uint64(len(txs))
 		}
 	}()
 
@@ -323,7 +344,7 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 	go func() {
 		var (
 			done = make(map[uint64]*blockTraceResult)
-			next = origin + 1
+			next = start.NumberU64() + 1
 		)
 		for res := range results {
 			// Queue up next received result
@@ -334,9 +355,6 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 			}
 			done[uint64(result.Block)] = result
 
-			// Dereference any paret tries held in memory by this task
-			database.TrieDB().Dereference(res.rootref)
-
 			// Stream completed traces to the user, aborting on the first error
 			for result, ok := done[next]; ok; result, ok = done[next] {
 				if len(result.Traces) > 0 || next == end.NumberU64() {
@@ -352,38 +370,27 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 
 // TraceBlockByNumber returns the structured logs created during the execution of
 // EVM and returns them as a JSON object.
-func (api *PrivateDebugAPI) TraceBlockByNumber(ctx context.Context, number rpc.BlockNumber, config *TraceConfig) ([]*txTraceResult, error) {
-	// Fetch the block that we want to trace
-	var block *types.Block
-
-	switch number {
-	case rpc.PendingBlockNumber:
-		block = api.eth.miner.PendingBlock()
-	case rpc.LatestBlockNumber:
-		block = api.eth.blockchain.CurrentBlock()
-	default:
-		block = api.eth.blockchain.GetBlockByNumber(uint64(number))
-	}
-	// Trace the block if it was found
-	if block == nil {
-		return nil, fmt.Errorf("block #%d not found", number)
+func (api *API) TraceBlockByNumber(ctx context.Context, number rpc.BlockNumber, config *TraceConfig) ([]*txTraceResult, error) {
+	block, err := api.blockByNumber(ctx, number)
+	if err != nil {
+		return nil, err
 	}
 	return api.traceBlock(ctx, block, config)
 }
 
 // TraceBlockByHash returns the structured logs created during the execution of
 // EVM and returns them as a JSON object.
-func (api *PrivateDebugAPI) TraceBlockByHash(ctx context.Context, hash common.Hash, config *TraceConfig) ([]*txTraceResult, error) {
-	block := api.eth.blockchain.GetBlockByHash(hash)
-	if block == nil {
-		return nil, fmt.Errorf("block %#x not found", hash)
+func (api *API) TraceBlockByHash(ctx context.Context, hash common.Hash, config *TraceConfig) ([]*txTraceResult, error) {
+	block, err := api.blockByHash(ctx, hash)
+	if err != nil {
+		return nil, err
 	}
 	return api.traceBlock(ctx, block, config)
 }
 
 // TraceBlock returns the structured logs created during the execution of EVM
 // and returns them as a JSON object.
-func (api *PrivateDebugAPI) TraceBlock(ctx context.Context, blob []byte, config *TraceConfig) ([]*txTraceResult, error) {
+func (api *API) TraceBlock(ctx context.Context, blob []byte, config *TraceConfig) ([]*txTraceResult, error) {
 	block := new(types.Block)
 	if err := rlp.Decode(bytes.NewReader(blob), block); err != nil {
 		return nil, fmt.Errorf("could not decode block: %v", err)
@@ -393,7 +400,7 @@ func (api *PrivateDebugAPI) TraceBlock(ctx context.Context, blob []byte, config
 
 // TraceBlockFromFile returns the structured logs created during the execution of
 // EVM and returns them as a JSON object.
-func (api *PrivateDebugAPI) TraceBlockFromFile(ctx context.Context, file string, config *TraceConfig) ([]*txTraceResult, error) {
+func (api *API) TraceBlockFromFile(ctx context.Context, file string, config *TraceConfig) ([]*txTraceResult, error) {
 	blob, err := ioutil.ReadFile(file)
 	if err != nil {
 		return nil, fmt.Errorf("could not read file: %v", err)
@@ -404,8 +411,8 @@ func (api *PrivateDebugAPI) TraceBlockFromFile(ctx context.Context, file string,
 // TraceBadBlock returns the structured logs created during the execution of
 // EVM against a block pulled from the pool of bad ones and returns them as a JSON
 // object.
-func (api *PrivateDebugAPI) TraceBadBlock(ctx context.Context, hash common.Hash, config *TraceConfig) ([]*txTraceResult, error) {
-	for _, block := range rawdb.ReadAllBadBlocks(api.eth.chainDb) {
+func (api *API) TraceBadBlock(ctx context.Context, hash common.Hash, config *TraceConfig) ([]*txTraceResult, error) {
+	for _, block := range rawdb.ReadAllBadBlocks(api.backend.ChainDb()) {
 		if block.Hash() == hash {
 			return api.traceBlock(ctx, block, config)
 		}
@@ -416,10 +423,10 @@ func (api *PrivateDebugAPI) TraceBadBlock(ctx context.Context, hash common.Hash,
 // StandardTraceBlockToFile dumps the structured logs created during the
 // execution of EVM to the local file system and returns a list of files
 // to the caller.
-func (api *PrivateDebugAPI) StandardTraceBlockToFile(ctx context.Context, hash common.Hash, config *StdTraceConfig) ([]string, error) {
-	block := api.eth.blockchain.GetBlockByHash(hash)
-	if block == nil {
-		return nil, fmt.Errorf("block %#x not found", hash)
+func (api *API) StandardTraceBlockToFile(ctx context.Context, hash common.Hash, config *StdTraceConfig) ([]string, error) {
+	block, err := api.blockByHash(ctx, hash)
+	if err != nil {
+		return nil, err
 	}
 	return api.standardTraceBlockToFile(ctx, block, config)
 }
@@ -427,8 +434,8 @@ func (api *PrivateDebugAPI) StandardTraceBlockToFile(ctx context.Context, hash c
 // StandardTraceBadBlockToFile dumps the structured logs created during the
 // execution of EVM against a block pulled from the pool of bad ones to the
 // local file system and returns a list of files to the caller.
-func (api *PrivateDebugAPI) StandardTraceBadBlockToFile(ctx context.Context, hash common.Hash, config *StdTraceConfig) ([]string, error) {
-	for _, block := range rawdb.ReadAllBadBlocks(api.eth.chainDb) {
+func (api *API) StandardTraceBadBlockToFile(ctx context.Context, hash common.Hash, config *StdTraceConfig) ([]string, error) {
+	for _, block := range rawdb.ReadAllBadBlocks(api.backend.ChainDb()) {
 		if block.Hash() == hash {
 			return api.standardTraceBlockToFile(ctx, block, config)
 		}
@@ -439,27 +446,27 @@ func (api *PrivateDebugAPI) StandardTraceBadBlockToFile(ctx context.Context, has
 // traceBlock configures a new tracer according to the provided configuration, and
 // executes all the transactions contained within. The return value will be one item
 // per transaction, dependent on the requestd tracer.
-func (api *PrivateDebugAPI) traceBlock(ctx context.Context, block *types.Block, config *TraceConfig) ([]*txTraceResult, error) {
-	// Create the parent state database
-	if err := api.eth.engine.VerifyHeader(api.eth.blockchain, block.Header(), true); err != nil {
-		return nil, err
+func (api *API) traceBlock(ctx context.Context, block *types.Block, config *TraceConfig) ([]*txTraceResult, error) {
+	if block.NumberU64() == 0 {
+		return nil, errors.New("genesis is not traceable")
 	}
-	parent := api.eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
-	if parent == nil {
-		return nil, fmt.Errorf("parent %#x not found", block.ParentHash())
+	parent, err := api.blockByNumberAndHash(ctx, rpc.BlockNumber(block.NumberU64()-1), block.ParentHash())
+	if err != nil {
+		return nil, err
 	}
 	reexec := defaultTraceReexec
 	if config != nil && config.Reexec != nil {
 		reexec = *config.Reexec
 	}
-	statedb, err := api.computeStateDB(parent, reexec)
+	statedb, release, err := api.backend.StateAtBlock(ctx, parent, reexec)
 	if err != nil {
 		return nil, err
 	}
+	defer release()
+
 	// Execute all the transaction contained within the block concurrently
 	var (
-		signer = types.MakeSigner(api.eth.blockchain.Config(), block.Number())
-
+		signer  = types.MakeSigner(api.backend.ChainConfig(), block.Number())
 		txs     = block.Transactions()
 		results = make([]*txTraceResult, len(txs))
 
@@ -470,7 +477,7 @@ func (api *PrivateDebugAPI) traceBlock(ctx context.Context, block *types.Block,
 	if threads > len(txs) {
 		threads = len(txs)
 	}
-	blockCtx := core.NewEVMBlockContext(block.Header(), api.eth.blockchain, nil)
+	blockCtx := core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
 	for th := 0; th < threads; th++ {
 		pend.Add(1)
 		go func() {
@@ -497,7 +504,7 @@ func (api *PrivateDebugAPI) traceBlock(ctx context.Context, block *types.Block,
 		msg, _ := tx.AsMessage(signer)
 		txContext := core.NewEVMTxContext(msg)
 
-		vmenv := vm.NewEVM(blockCtx, txContext, statedb, api.eth.blockchain.Config(), vm.Config{})
+		vmenv := vm.NewEVM(blockCtx, txContext, statedb, api.backend.ChainConfig(), vm.Config{})
 		if _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(msg.Gas())); err != nil {
 			failed = err
 			break
@@ -519,29 +526,30 @@ func (api *PrivateDebugAPI) traceBlock(ctx context.Context, block *types.Block,
 // standardTraceBlockToFile configures a new tracer which uses standard JSON output,
 // and traces either a full block or an individual transaction. The return value will
 // be one filename per transaction traced.
-func (api *PrivateDebugAPI) standardTraceBlockToFile(ctx context.Context, block *types.Block, config *StdTraceConfig) ([]string, error) {
+func (api *API) standardTraceBlockToFile(ctx context.Context, block *types.Block, config *StdTraceConfig) ([]string, error) {
 	// If we're tracing a single transaction, make sure it's present
 	if config != nil && config.TxHash != (common.Hash{}) {
 		if !containsTx(block, config.TxHash) {
 			return nil, fmt.Errorf("transaction %#x not found in block", config.TxHash)
 		}
 	}
-	// Create the parent state database
-	if err := api.eth.engine.VerifyHeader(api.eth.blockchain, block.Header(), true); err != nil {
-		return nil, err
+	if block.NumberU64() == 0 {
+		return nil, errors.New("genesis is not traceable")
 	}
-	parent := api.eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
-	if parent == nil {
-		return nil, fmt.Errorf("parent %#x not found", block.ParentHash())
+	parent, err := api.blockByNumberAndHash(ctx, rpc.BlockNumber(block.NumberU64()-1), block.ParentHash())
+	if err != nil {
+		return nil, err
 	}
 	reexec := defaultTraceReexec
 	if config != nil && config.Reexec != nil {
 		reexec = *config.Reexec
 	}
-	statedb, err := api.computeStateDB(parent, reexec)
+	statedb, release, err := api.backend.StateAtBlock(ctx, parent, reexec)
 	if err != nil {
 		return nil, err
 	}
+	defer release()
+
 	// Retrieve the tracing configurations, or use default values
 	var (
 		logConfig vm.LogConfig
@@ -555,10 +563,10 @@ func (api *PrivateDebugAPI) standardTraceBlockToFile(ctx context.Context, block
 
 	// Execute transaction, either tracing all or just the requested one
 	var (
-		signer      = types.MakeSigner(api.eth.blockchain.Config(), block.Number())
 		dumps       []string
-		chainConfig = api.eth.blockchain.Config()
-		vmctx       = core.NewEVMBlockContext(block.Header(), api.eth.blockchain, nil)
+		signer      = types.MakeSigner(api.backend.ChainConfig(), block.Number())
+		chainConfig = api.backend.ChainConfig()
+		vmctx       = core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
 		canon       = true
 	)
 	// Check if there are any overrides: the caller may wish to enable a future
@@ -645,139 +653,73 @@ func containsTx(block *types.Block, hash common.Hash) bool {
 	return false
 }
 
-// computeStateDB 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.
-func (api *PrivateDebugAPI) computeStateDB(block *types.Block, reexec uint64) (*state.StateDB, error) {
-	// If we have the state fully available, use that
-	statedb, err := api.eth.blockchain.StateAt(block.Root())
-	if err == nil {
-		return statedb, nil
-	}
-	// Otherwise try to reexec blocks until we find a state or reach our limit
-	origin := block.NumberU64()
-	database := state.NewDatabaseWithConfig(api.eth.ChainDb(), &trie.Config{Cache: 16, Preimages: true})
-
-	for i := uint64(0); i < reexec; i++ {
-		block = api.eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
-		if block == nil {
-			break
-		}
-		if statedb, err = state.New(block.Root(), database, nil); err == nil {
-			break
-		}
-	}
-	if err != nil {
-		switch err.(type) {
-		case *trie.MissingNodeError:
-			return nil, fmt.Errorf("required historical state unavailable (reexec=%d)", reexec)
-		default:
-			return nil, err
-		}
-	}
-	// State was available at historical point, regenerate
-	var (
-		start  = time.Now()
-		logged time.Time
-		proot  common.Hash
-	)
-	for block.NumberU64() < origin {
-		// Print progress logs if long enough time elapsed
-		if time.Since(logged) > 8*time.Second {
-			log.Info("Regenerating historical state", "block", block.NumberU64()+1, "target", origin, "remaining", origin-block.NumberU64()-1, "elapsed", time.Since(start))
-			logged = time.Now()
-		}
-		// Retrieve the next block to regenerate and process it
-		if block = api.eth.blockchain.GetBlockByNumber(block.NumberU64() + 1); block == nil {
-			return nil, fmt.Errorf("block #%d not found", block.NumberU64()+1)
-		}
-		_, _, _, err := api.eth.blockchain.Processor().Process(block, statedb, vm.Config{})
-		if err != nil {
-			return nil, fmt.Errorf("processing block %d failed: %v", block.NumberU64(), err)
-		}
-		// Finalize the state so any modifications are written to the trie
-		root, err := statedb.Commit(api.eth.blockchain.Config().IsEIP158(block.Number()))
-		if err != nil {
-			return nil, err
-		}
-		statedb, err = state.New(root, database, nil)
-		if err != nil {
-			return nil, fmt.Errorf("state reset after block %d failed: %v", block.NumberU64(), err)
-		}
-		database.TrieDB().Reference(root, common.Hash{})
-		if proot != (common.Hash{}) {
-			database.TrieDB().Dereference(proot)
-		}
-		proot = root
-	}
-	nodes, imgs := database.TrieDB().Size()
-	log.Info("Historical state regenerated", "block", block.NumberU64(), "elapsed", time.Since(start), "nodes", nodes, "preimages", imgs)
-	return statedb, nil
-}
-
 // TraceTransaction returns the structured logs created during the execution of EVM
 // and returns them as a JSON object.
-func (api *PrivateDebugAPI) TraceTransaction(ctx context.Context, hash common.Hash, config *TraceConfig) (interface{}, error) {
-	// Retrieve the transaction and assemble its EVM context
-	tx, blockHash, _, index := rawdb.ReadTransaction(api.eth.ChainDb(), hash)
-	if tx == nil {
-		return nil, fmt.Errorf("transaction %#x not found", hash)
+func (api *API) TraceTransaction(ctx context.Context, hash common.Hash, config *TraceConfig) (interface{}, error) {
+	_, blockHash, blockNumber, index, err := api.backend.GetTransaction(ctx, hash)
+	if err != nil {
+		return nil, err
+	}
+	// It shouldn't happen in practice.
+	if blockNumber == 0 {
+		return nil, errors.New("genesis is not traceable")
 	}
 	reexec := defaultTraceReexec
 	if config != nil && config.Reexec != nil {
 		reexec = *config.Reexec
 	}
-	// Retrieve the block
-	block := api.eth.blockchain.GetBlockByHash(blockHash)
-	if block == nil {
-		return nil, fmt.Errorf("block %#x not found", blockHash)
+	block, err := api.blockByNumberAndHash(ctx, rpc.BlockNumber(blockNumber), blockHash)
+	if err != nil {
+		return nil, err
 	}
-	msg, vmctx, statedb, err := api.computeTxEnv(block, int(index), reexec)
+	msg, vmctx, statedb, release, err := api.backend.StateAtTransaction(ctx, block, int(index), reexec)
 	if err != nil {
 		return nil, err
 	}
-	// Trace the transaction and return
+	defer release()
+
 	return api.traceTx(ctx, msg, vmctx, statedb, config)
 }
 
-// TraceCall lets you trace a given eth_call. It collects the structured logs created during the execution of EVM
-// if the given transaction was added on top of the provided block and returns them as a JSON object.
+// TraceCall lets you trace a given eth_call. It collects the structured logs
+// created during the execution of EVM if the given transaction was added on
+// top of the provided block and returns them as a JSON object.
 // You can provide -2 as a block number to trace on top of the pending block.
-func (api *PrivateDebugAPI) TraceCall(ctx context.Context, args ethapi.CallArgs, blockNrOrHash rpc.BlockNumberOrHash, config *TraceConfig) (interface{}, error) {
-	// First try to retrieve the state
-	statedb, header, err := api.eth.APIBackend.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
+func (api *API) TraceCall(ctx context.Context, args ethapi.CallArgs, blockNrOrHash rpc.BlockNumberOrHash, config *TraceConfig) (interface{}, error) {
+	// Try to retrieve the specified block
+	var (
+		err   error
+		block *types.Block
+	)
+	if hash, ok := blockNrOrHash.Hash(); ok {
+		block, err = api.blockByHash(ctx, hash)
+	} else if number, ok := blockNrOrHash.Number(); ok {
+		block, err = api.blockByNumber(ctx, number)
+	}
 	if err != nil {
-		// Try to retrieve the specified block
-		var block *types.Block
-		if hash, ok := blockNrOrHash.Hash(); ok {
-			block = api.eth.blockchain.GetBlockByHash(hash)
-		} else if number, ok := blockNrOrHash.Number(); ok {
-			block = api.eth.blockchain.GetBlockByNumber(uint64(number))
-		}
-		if block == nil {
-			return nil, fmt.Errorf("block %v not found: %v", blockNrOrHash, err)
-		}
-		// try to recompute the state
-		reexec := defaultTraceReexec
-		if config != nil && config.Reexec != nil {
-			reexec = *config.Reexec
-		}
-		_, _, statedb, err = api.computeTxEnv(block, 0, reexec)
-		if err != nil {
-			return nil, err
-		}
+		return nil, err
+	}
+	// try to recompute the state
+	reexec := defaultTraceReexec
+	if config != nil && config.Reexec != nil {
+		reexec = *config.Reexec
 	}
+	statedb, release, err := api.backend.StateAtBlock(ctx, block, reexec)
+	if err != nil {
+		return nil, err
+	}
+	defer release()
 
 	// Execute the trace
-	msg := args.ToMessage(api.eth.APIBackend.RPCGasCap())
-	vmctx := core.NewEVMBlockContext(header, api.eth.blockchain, nil)
+	msg := args.ToMessage(api.backend.RPCGasCap())
+	vmctx := core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
 	return api.traceTx(ctx, msg, vmctx, statedb, config)
 }
 
 // traceTx configures a new tracer according to the provided configuration, and
 // executes the given message in the provided environment. The return value will
 // be tracer dependent.
-func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, vmctx vm.BlockContext, statedb *state.StateDB, config *TraceConfig) (interface{}, error) {
+func (api *API) traceTx(ctx context.Context, message core.Message, vmctx vm.BlockContext, statedb *state.StateDB, config *TraceConfig) (interface{}, error) {
 	// Assemble the structured logger or the JavaScript tracer
 	var (
 		tracer    vm.Tracer
@@ -794,14 +736,14 @@ func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, v
 			}
 		}
 		// Constuct the JavaScript tracer to execute with
-		if tracer, err = tracers.New(*config.Tracer, txContext); err != nil {
+		if tracer, err = New(*config.Tracer, txContext); err != nil {
 			return nil, err
 		}
 		// Handle timeouts and RPC cancellations
 		deadlineCtx, cancel := context.WithTimeout(ctx, timeout)
 		go func() {
 			<-deadlineCtx.Done()
-			tracer.(*tracers.Tracer).Stop(errors.New("execution timeout"))
+			tracer.(*Tracer).Stop(errors.New("execution timeout"))
 		}()
 		defer cancel()
 
@@ -812,7 +754,7 @@ func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, v
 		tracer = vm.NewStructLogger(config.LogConfig)
 	}
 	// Run the transaction with tracing enabled.
-	vmenv := vm.NewEVM(vmctx, txContext, statedb, api.eth.blockchain.Config(), vm.Config{Debug: true, Tracer: tracer})
+	vmenv := vm.NewEVM(vmctx, txContext, statedb, api.backend.ChainConfig(), vm.Config{Debug: true, Tracer: tracer})
 
 	result, err := core.ApplyMessage(vmenv, message, new(core.GasPool).AddGas(message.Gas()))
 	if err != nil {
@@ -833,7 +775,7 @@ func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, v
 			StructLogs:  ethapi.FormatLogs(tracer.StructLogs()),
 		}, nil
 
-	case *tracers.Tracer:
+	case *Tracer:
 		return tracer.GetResult()
 
 	default:
@@ -841,41 +783,15 @@ func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, v
 	}
 }
 
-// computeTxEnv returns the execution environment of a certain transaction.
-func (api *PrivateDebugAPI) computeTxEnv(block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, error) {
-	// Create the parent state database
-	parent := api.eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
-	if parent == nil {
-		return nil, vm.BlockContext{}, nil, fmt.Errorf("parent %#x not found", block.ParentHash())
-	}
-	statedb, err := api.computeStateDB(parent, reexec)
-	if err != nil {
-		return nil, vm.BlockContext{}, nil, err
-	}
-
-	if txIndex == 0 && len(block.Transactions()) == 0 {
-		return nil, vm.BlockContext{}, statedb, nil
-	}
-
-	// Recompute transactions up to the target index.
-	signer := types.MakeSigner(api.eth.blockchain.Config(), block.Number())
-
-	for idx, tx := range block.Transactions() {
-		// Assemble the transaction call message and return if the requested offset
-		msg, _ := tx.AsMessage(signer)
-		txContext := core.NewEVMTxContext(msg)
-		context := core.NewEVMBlockContext(block.Header(), api.eth.blockchain, nil)
-		if idx == txIndex {
-			return msg, context, statedb, nil
-		}
-		// Not yet the searched for transaction, execute on top of the current state
-		vmenv := vm.NewEVM(context, txContext, statedb, api.eth.blockchain.Config(), vm.Config{})
-		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)
-		}
-		// 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()))
+// APIs return the collection of RPC services the tracer package offers.
+func APIs(backend Backend) []rpc.API {
+	// Append all the local APIs and return
+	return []rpc.API{
+		{
+			Namespace: "debug",
+			Version:   "1.0",
+			Service:   NewAPI(backend),
+			Public:    false,
+		},
 	}
-	return nil, vm.BlockContext{}, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, block.Hash())
 }

eth/tracers/api_test.go

@@ -0,0 +1,487 @@
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package tracers
+
+import (
+	"bytes"
+	"context"
+	"crypto/ecdsa"
+	"errors"
+	"fmt"
+	"math/big"
+	"reflect"
+	"sort"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/rawdb"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/internal/ethapi"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/rpc"
+)
+
+var (
+	errStateNotFound       = errors.New("state not found")
+	errBlockNotFound       = errors.New("block not found")
+	errTransactionNotFound = errors.New("transaction not found")
+)
+
+type testBackend struct {
+	chainConfig *params.ChainConfig
+	engine      consensus.Engine
+	chaindb     ethdb.Database
+	chain       *core.BlockChain
+}
+
+func newTestBackend(t *testing.T, n int, gspec *core.Genesis, generator func(i int, b *core.BlockGen)) *testBackend {
+	backend := &testBackend{
+		chainConfig: params.TestChainConfig,
+		engine:      ethash.NewFaker(),
+		chaindb:     rawdb.NewMemoryDatabase(),
+	}
+	// Generate blocks for testing
+	gspec.Config = backend.chainConfig
+	var (
+		gendb   = rawdb.NewMemoryDatabase()
+		genesis = gspec.MustCommit(gendb)
+	)
+	blocks, _ := core.GenerateChain(backend.chainConfig, genesis, backend.engine, gendb, n, generator)
+
+	// Import the canonical chain
+	gspec.MustCommit(backend.chaindb)
+	cacheConfig := &core.CacheConfig{
+		TrieCleanLimit:    256,
+		TrieDirtyLimit:    256,
+		TrieTimeLimit:     5 * time.Minute,
+		SnapshotLimit:     0,
+		TrieDirtyDisabled: true, // Archive mode
+	}
+	chain, err := core.NewBlockChain(backend.chaindb, cacheConfig, backend.chainConfig, backend.engine, vm.Config{}, nil, nil)
+	if err != nil {
+		t.Fatalf("failed to create tester chain: %v", err)
+	}
+	if n, err := chain.InsertChain(blocks); err != nil {
+		t.Fatalf("block %d: failed to insert into chain: %v", n, err)
+	}
+	backend.chain = chain
+	return backend
+}
+
+func (b *testBackend) HeaderByHash(ctx context.Context, hash common.Hash) (*types.Header, error) {
+	return b.chain.GetHeaderByHash(hash), nil
+}
+
+func (b *testBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error) {
+	if number == rpc.PendingBlockNumber || number == rpc.LatestBlockNumber {
+		return b.chain.CurrentHeader(), nil
+	}
+	return b.chain.GetHeaderByNumber(uint64(number)), nil
+}
+
+func (b *testBackend) BlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error) {
+	return b.chain.GetBlockByHash(hash), nil
+}
+
+func (b *testBackend) BlockByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Block, error) {
+	if number == rpc.PendingBlockNumber || number == rpc.LatestBlockNumber {
+		return b.chain.CurrentBlock(), nil
+	}
+	return b.chain.GetBlockByNumber(uint64(number)), nil
+}
+
+func (b *testBackend) GetTransaction(ctx context.Context, txHash common.Hash) (*types.Transaction, common.Hash, uint64, uint64, error) {
+	tx, hash, blockNumber, index := rawdb.ReadTransaction(b.chaindb, txHash)
+	if tx == nil {
+		return nil, common.Hash{}, 0, 0, errTransactionNotFound
+	}
+	return tx, hash, blockNumber, index, nil
+}
+
+func (b *testBackend) RPCGasCap() uint64 {
+	return 25000000
+}
+
+func (b *testBackend) ChainConfig() *params.ChainConfig {
+	return b.chainConfig
+}
+
+func (b *testBackend) Engine() consensus.Engine {
+	return b.engine
+}
+
+func (b *testBackend) ChainDb() ethdb.Database {
+	return b.chaindb
+}
+
+func (b *testBackend) StateAtBlock(ctx context.Context, block *types.Block, reexec uint64) (*state.StateDB, func(), error) {
+	statedb, err := b.chain.StateAt(block.Root())
+	if err != nil {
+		return nil, nil, errStateNotFound
+	}
+	return statedb, func() {}, nil
+}
+
+func (b *testBackend) StateAtTransaction(ctx context.Context, block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, func(), error) {
+	parent := b.chain.GetBlock(block.ParentHash(), block.NumberU64()-1)
+	if parent == nil {
+		return nil, vm.BlockContext{}, nil, nil, errBlockNotFound
+	}
+	statedb, err := b.chain.StateAt(parent.Root())
+	if err != nil {
+		return nil, vm.BlockContext{}, nil, nil, errStateNotFound
+	}
+	if txIndex == 0 && len(block.Transactions()) == 0 {
+		return nil, vm.BlockContext{}, statedb, func() {}, nil
+	}
+	// Recompute transactions up to the target index.
+	signer := types.MakeSigner(b.chainConfig, block.Number())
+	for idx, tx := range block.Transactions() {
+		msg, _ := tx.AsMessage(signer)
+		txContext := core.NewEVMTxContext(msg)
+		context := core.NewEVMBlockContext(block.Header(), b.chain, nil)
+		if idx == txIndex {
+			return msg, context, statedb, func() {}, nil
+		}
+		vmenv := vm.NewEVM(context, txContext, statedb, b.chainConfig, vm.Config{})
+		if _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(tx.Gas())); err != nil {
+			return nil, vm.BlockContext{}, nil, nil, fmt.Errorf("transaction %#x failed: %v", tx.Hash(), err)
+		}
+		statedb.Finalise(vmenv.ChainConfig().IsEIP158(block.Number()))
+	}
+	return nil, vm.BlockContext{}, nil, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, block.Hash())
+}
+
+func (b *testBackend) StatesInRange(ctx context.Context, fromBlock *types.Block, toBlock *types.Block, reexec uint64) ([]*state.StateDB, func(), error) {
+	var result []*state.StateDB
+	for number := fromBlock.NumberU64(); number <= toBlock.NumberU64(); number += 1 {
+		block := b.chain.GetBlockByNumber(number)
+		if block == nil {
+			return nil, nil, errBlockNotFound
+		}
+		statedb, err := b.chain.StateAt(block.Root())
+		if err != nil {
+			return nil, nil, errStateNotFound
+		}
+		result = append(result, statedb)
+	}
+	return result, func() {}, nil
+}
+
+func TestTraceCall(t *testing.T) {
+	t.Parallel()
+
+	// Initialize test accounts
+	accounts := newAccounts(3)
+	genesis := &core.Genesis{Alloc: core.GenesisAlloc{
+		accounts[0].addr: {Balance: big.NewInt(params.Ether)},
+		accounts[1].addr: {Balance: big.NewInt(params.Ether)},
+		accounts[2].addr: {Balance: big.NewInt(params.Ether)},
+	}}
+	genBlocks := 10
+	signer := types.HomesteadSigner{}
+	api := NewAPI(newTestBackend(t, genBlocks, genesis, func(i int, b *core.BlockGen) {
+		// Transfer from account[0] to account[1]
+		//    value: 1000 wei
+		//    fee:   0 wei
+		tx, _ := types.SignTx(types.NewTransaction(uint64(i), accounts[1].addr, big.NewInt(1000), params.TxGas, big.NewInt(0), nil), signer, accounts[0].key)
+		b.AddTx(tx)
+	}))
+
+	var testSuite = []struct {
+		blockNumber rpc.BlockNumber
+		call        ethapi.CallArgs
+		config      *TraceConfig
+		expectErr   error
+		expect      interface{}
+	}{
+		// Standard JSON trace upon the genesis, plain transfer.
+		{
+			blockNumber: rpc.BlockNumber(0),
+			call: ethapi.CallArgs{
+				From:  &accounts[0].addr,
+				To:    &accounts[1].addr,
+				Value: (*hexutil.Big)(big.NewInt(1000)),
+			},
+			config:    nil,
+			expectErr: nil,
+			expect: &ethapi.ExecutionResult{
+				Gas:         params.TxGas,
+				Failed:      false,
+				ReturnValue: "",
+				StructLogs:  []ethapi.StructLogRes{},
+			},
+		},
+		// Standard JSON trace upon the head, plain transfer.
+		{
+			blockNumber: rpc.BlockNumber(genBlocks),
+			call: ethapi.CallArgs{
+				From:  &accounts[0].addr,
+				To:    &accounts[1].addr,
+				Value: (*hexutil.Big)(big.NewInt(1000)),
+			},
+			config:    nil,
+			expectErr: nil,
+			expect: &ethapi.ExecutionResult{
+				Gas:         params.TxGas,
+				Failed:      false,
+				ReturnValue: "",
+				StructLogs:  []ethapi.StructLogRes{},
+			},
+		},
+		// Standard JSON trace upon the non-existent block, error expects
+		{
+			blockNumber: rpc.BlockNumber(genBlocks + 1),
+			call: ethapi.CallArgs{
+				From:  &accounts[0].addr,
+				To:    &accounts[1].addr,
+				Value: (*hexutil.Big)(big.NewInt(1000)),
+			},
+			config:    nil,
+			expectErr: fmt.Errorf("block #%d not found", genBlocks+1),
+			expect:    nil,
+		},
+		// Standard JSON trace upon the latest block
+		{
+			blockNumber: rpc.LatestBlockNumber,
+			call: ethapi.CallArgs{
+				From:  &accounts[0].addr,
+				To:    &accounts[1].addr,
+				Value: (*hexutil.Big)(big.NewInt(1000)),
+			},
+			config:    nil,
+			expectErr: nil,
+			expect: &ethapi.ExecutionResult{
+				Gas:         params.TxGas,
+				Failed:      false,
+				ReturnValue: "",
+				StructLogs:  []ethapi.StructLogRes{},
+			},
+		},
+		// Standard JSON trace upon the pending block
+		{
+			blockNumber: rpc.PendingBlockNumber,
+			call: ethapi.CallArgs{
+				From:  &accounts[0].addr,
+				To:    &accounts[1].addr,
+				Value: (*hexutil.Big)(big.NewInt(1000)),
+			},
+			config:    nil,
+			expectErr: nil,
+			expect: &ethapi.ExecutionResult{
+				Gas:         params.TxGas,
+				Failed:      false,
+				ReturnValue: "",
+				StructLogs:  []ethapi.StructLogRes{},
+			},
+		},
+	}
+	for _, testspec := range testSuite {
+		result, err := api.TraceCall(context.Background(), testspec.call, rpc.BlockNumberOrHash{BlockNumber: &testspec.blockNumber}, testspec.config)
+		if testspec.expectErr != nil {
+			if err == nil {
+				t.Errorf("Expect error %v, get nothing", testspec.expectErr)
+				continue
+			}
+			if !reflect.DeepEqual(err, testspec.expectErr) {
+				t.Errorf("Error mismatch, want %v, get %v", testspec.expectErr, err)
+			}
+		} else {
+			if err != nil {
+				t.Errorf("Expect no error, get %v", err)
+				continue
+			}
+			if !reflect.DeepEqual(result, testspec.expect) {
+				t.Errorf("Result mismatch, want %v, get %v", testspec.expect, result)
+			}
+		}
+	}
+}
+
+func TestTraceTransaction(t *testing.T) {
+	t.Parallel()
+
+	// Initialize test accounts
+	accounts := newAccounts(2)
+	genesis := &core.Genesis{Alloc: core.GenesisAlloc{
+		accounts[0].addr: {Balance: big.NewInt(params.Ether)},
+		accounts[1].addr: {Balance: big.NewInt(params.Ether)},
+	}}
+	target := common.Hash{}
+	signer := types.HomesteadSigner{}
+	api := NewAPI(newTestBackend(t, 1, genesis, func(i int, b *core.BlockGen) {
+		// Transfer from account[0] to account[1]
+		//    value: 1000 wei
+		//    fee:   0 wei
+		tx, _ := types.SignTx(types.NewTransaction(uint64(i), accounts[1].addr, big.NewInt(1000), params.TxGas, big.NewInt(0), nil), signer, accounts[0].key)
+		b.AddTx(tx)
+		target = tx.Hash()
+	}))
+	result, err := api.TraceTransaction(context.Background(), target, nil)
+	if err != nil {
+		t.Errorf("Failed to trace transaction %v", err)
+	}
+	if !reflect.DeepEqual(result, &ethapi.ExecutionResult{
+		Gas:         params.TxGas,
+		Failed:      false,
+		ReturnValue: "",
+		StructLogs:  []ethapi.StructLogRes{},
+	}) {
+		t.Error("Transaction tracing result is different")
+	}
+}
+
+func TestTraceBlock(t *testing.T) {
+	t.Parallel()
+
+	// Initialize test accounts
+	accounts := newAccounts(3)
+	genesis := &core.Genesis{Alloc: core.GenesisAlloc{
+		accounts[0].addr: {Balance: big.NewInt(params.Ether)},
+		accounts[1].addr: {Balance: big.NewInt(params.Ether)},
+		accounts[2].addr: {Balance: big.NewInt(params.Ether)},
+	}}
+	genBlocks := 10
+	signer := types.HomesteadSigner{}
+	api := NewAPI(newTestBackend(t, genBlocks, genesis, func(i int, b *core.BlockGen) {
+		// Transfer from account[0] to account[1]
+		//    value: 1000 wei
+		//    fee:   0 wei
+		tx, _ := types.SignTx(types.NewTransaction(uint64(i), accounts[1].addr, big.NewInt(1000), params.TxGas, big.NewInt(0), nil), signer, accounts[0].key)
+		b.AddTx(tx)
+	}))
+
+	var testSuite = []struct {
+		blockNumber rpc.BlockNumber
+		config      *TraceConfig
+		expect      interface{}
+		expectErr   error
+	}{
+		// Trace genesis block, expect error
+		{
+			blockNumber: rpc.BlockNumber(0),
+			config:      nil,
+			expect:      nil,
+			expectErr:   errors.New("genesis is not traceable"),
+		},
+		// Trace head block
+		{
+			blockNumber: rpc.BlockNumber(genBlocks),
+			config:      nil,
+			expectErr:   nil,
+			expect: []*txTraceResult{
+				{
+					Result: &ethapi.ExecutionResult{
+						Gas:         params.TxGas,
+						Failed:      false,
+						ReturnValue: "",
+						StructLogs:  []ethapi.StructLogRes{},
+					},
+				},
+			},
+		},
+		// Trace non-existent block
+		{
+			blockNumber: rpc.BlockNumber(genBlocks + 1),
+			config:      nil,
+			expectErr:   fmt.Errorf("block #%d not found", genBlocks+1),
+			expect:      nil,
+		},
+		// Trace latest block
+		{
+			blockNumber: rpc.LatestBlockNumber,
+			config:      nil,
+			expectErr:   nil,
+			expect: []*txTraceResult{
+				{
+					Result: &ethapi.ExecutionResult{
+						Gas:         params.TxGas,
+						Failed:      false,
+						ReturnValue: "",
+						StructLogs:  []ethapi.StructLogRes{},
+					},
+				},
+			},
+		},
+		// Trace pending block
+		{
+			blockNumber: rpc.PendingBlockNumber,
+			config:      nil,
+			expectErr:   nil,
+			expect: []*txTraceResult{
+				{
+					Result: &ethapi.ExecutionResult{
+						Gas:         params.TxGas,
+						Failed:      false,
+						ReturnValue: "",
+						StructLogs:  []ethapi.StructLogRes{},
+					},
+				},
+			},
+		},
+	}
+	for _, testspec := range testSuite {
+		result, err := api.TraceBlockByNumber(context.Background(), testspec.blockNumber, testspec.config)
+		if testspec.expectErr != nil {
+			if err == nil {
+				t.Errorf("Expect error %v, get nothing", testspec.expectErr)
+				continue
+			}
+			if !reflect.DeepEqual(err, testspec.expectErr) {
+				t.Errorf("Error mismatch, want %v, get %v", testspec.expectErr, err)
+			}
+		} else {
+			if err != nil {
+				t.Errorf("Expect no error, get %v", err)
+				continue
+			}
+			if !reflect.DeepEqual(result, testspec.expect) {
+				t.Errorf("Result mismatch, want %v, get %v", testspec.expect, result)
+			}
+		}
+	}
+}
+
+type Account struct {
+	key  *ecdsa.PrivateKey
+	addr common.Address
+}
+
+type Accounts []Account
+
+func (a Accounts) Len() int           { return len(a) }
+func (a Accounts) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a Accounts) Less(i, j int) bool { return bytes.Compare(a[i].addr.Bytes(), a[j].addr.Bytes()) < 0 }
+
+func newAccounts(n int) (accounts Accounts) {
+	for i := 0; i < n; i++ {
+		key, _ := crypto.GenerateKey()
+		addr := crypto.PubkeyToAddress(key.PublicKey)
+		accounts = append(accounts, Account{key: key, addr: addr})
+	}
+	sort.Sort(accounts)
+	return accounts
+}

les/api_backend.go

@@ -292,3 +292,15 @@ func (b *LesApiBackend) Engine() consensus.Engine {
 func (b *LesApiBackend) CurrentHeader() *types.Header {
 	return b.eth.blockchain.CurrentHeader()
 }
+
+func (b *LesApiBackend) StateAtBlock(ctx context.Context, block *types.Block, reexec uint64) (*state.StateDB, func(), error) {
+	return b.eth.stateAtBlock(ctx, block, reexec)
+}
+
+func (b *LesApiBackend) StatesInRange(ctx context.Context, fromBlock *types.Block, toBlock *types.Block, reexec uint64) ([]*state.StateDB, func(), error) {
+	return b.eth.statesInRange(ctx, fromBlock, toBlock, reexec)
+}
+
+func (b *LesApiBackend) StateAtTransaction(ctx context.Context, block *types.Block, txIndex int, reexec uint64) (core.Message, vm.BlockContext, *state.StateDB, func(), error) {
+	return b.eth.stateAtTransaction(ctx, block, txIndex, reexec)
+}

les/state_accessor.go

@@ -0,0 +1,88 @@
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package les
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/light"
+)
+
+// stateAtBlock retrieves the state database associated with a certain block.
+func (leth *LightEthereum) stateAtBlock(ctx context.Context, block *types.Block, reexec uint64) (*state.StateDB, func(), error) {
+	return light.NewState(ctx, block.Header(), leth.odr), func() {}, nil
+}
+
+// statesInRange retrieves a batch of state databases associated with the specific
+// block ranges.
+func (leth *LightEthereum) statesInRange(ctx context.Context, fromBlock *types.Block, toBlock *types.Block, reexec uint64) ([]*state.StateDB, func(), error) {
+	var states []*state.StateDB
+	for number := fromBlock.NumberU64(); number <= toBlock.NumberU64(); number++ {
+		header, err := leth.blockchain.GetHeaderByNumberOdr(ctx, number)
+		if err != nil {
+			return nil, nil, err
+		}
+		states = append(states, light.NewState(ctx, header, leth.odr))
+	}
+	return states, nil, nil
+}
+
+// stateAtTransaction returns the execution environment of a certain transaction.
+func (leth *LightEthereum) stateAtTransaction(ctx context.Context, 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, nil, errors.New("no transaction in genesis")
+	}
+	// Create the parent state database
+	parent, err := leth.blockchain.GetBlock(ctx, block.ParentHash(), block.NumberU64()-1)
+	if err != nil {
+		return nil, vm.BlockContext{}, nil, nil, err
+	}
+	statedb, _, err := leth.stateAtBlock(ctx, parent, reexec)
+	if err != nil {
+		return nil, vm.BlockContext{}, nil, nil, err
+	}
+	if txIndex == 0 && len(block.Transactions()) == 0 {
+		return nil, vm.BlockContext{}, statedb, func() {}, nil
+	}
+	// Recompute transactions up to the target index.
+	signer := types.MakeSigner(leth.blockchain.Config(), block.Number())
+	for idx, tx := range block.Transactions() {
+		// Assemble the transaction call message and return if the requested offset
+		msg, _ := tx.AsMessage(signer)
+		txContext := core.NewEVMTxContext(msg)
+		context := core.NewEVMBlockContext(block.Header(), leth.blockchain, nil)
+		if idx == txIndex {
+			return msg, context, statedb, func() {}, nil
+		}
+		// Not yet the searched for transaction, execute on top of the current state
+		vmenv := vm.NewEVM(context, txContext, statedb, leth.blockchain.Config(), vm.Config{})
+		if _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(tx.Gas())); err != nil {
+			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, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, block.Hash())
+}