eth, les: fix gas price oracle panic

eth/backend.go

@@ -18,6 +18,7 @@
 package eth
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"math/big"
@@ -215,18 +216,23 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 	eth.miner = miner.New(eth, &config.Miner, chainConfig, eth.EventMux(), eth.engine, eth.isLocalBlock)
 	eth.miner.SetExtra(makeExtraData(config.Miner.ExtraData))
 
-	eth.APIBackend = &EthAPIBackend{ctx.ExtRPCEnabled(), eth, nil}
 	gpoParams := config.GPO
 	if gpoParams.Default == nil {
 		gpoParams.Default = config.Miner.GasPrice
 	}
-	eth.APIBackend.gpo = gasprice.NewOracle(eth.APIBackend, gpoParams)
-
+	eth.APIBackend = &EthAPIBackend{
+		ctx.ExtRPCEnabled(), eth,
+		gasprice.NewOracle(gpoParams, chainConfig,
+			func() *types.Header { return eth.blockchain.CurrentHeader() },
+			func(ctx context.Context, number uint64) (*types.Block, error) {
+				return eth.blockchain.GetBlockByNumber(number), nil
+			},
+		),
+	}
 	eth.dialCandiates, err = eth.setupDiscovery(&ctx.Config.P2P)
 	if err != nil {
 		return nil, err
 	}
-
 	return eth, nil
 }
 

eth/gasprice/gasprice.go

@@ -24,9 +24,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/internal/ethapi"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/rpc"
 )
 
 var maxPrice = big.NewInt(500 * params.GWei)
@@ -37,26 +35,36 @@ type Config struct {
 	Default    *big.Int `toml:",omitempty"`
 }
 
+type (
+	// headHeaderRetrieverFn is a callback type for retrieving the head header from the local chain.
+	headHeaderRetrieverFn func() *types.Header
+
+	// blockRetrieverFn is a callback type for retrieving a block from the local chain or p2p network.
+	blockRetrieverFn func(context.Context, uint64) (*types.Block, error)
+)
+
 // Oracle recommends gas prices based on the content of recent
 // blocks. Suitable for both light and full clients.
 type Oracle struct {
-	backend   ethapi.Backend
-	lastHead  common.Hash
-	lastPrice *big.Int
-	cacheLock sync.RWMutex
-	fetchLock sync.Mutex
+	lastHead      common.Hash
+	lastPrice     *big.Int
+	cacheLock     sync.RWMutex
+	fetchLock     sync.Mutex
+	chainConfig   *params.ChainConfig
+	getHeadHeader headHeaderRetrieverFn
+	getBlock      blockRetrieverFn
 
 	checkBlocks, maxEmpty, maxBlocks int
 	percentile                       int
 }
 
 // NewOracle returns a new oracle.
-func NewOracle(backend ethapi.Backend, params Config) *Oracle {
-	blocks := params.Blocks
+func NewOracle(config Config, chainConfig *params.ChainConfig, getHeadHeader headHeaderRetrieverFn, getBlock blockRetrieverFn) *Oracle {
+	blocks := config.Blocks
 	if blocks < 1 {
 		blocks = 1
 	}
-	percent := params.Percentile
+	percent := config.Percentile
 	if percent < 0 {
 		percent = 0
 	}
@@ -64,12 +72,14 @@ func NewOracle(backend ethapi.Backend, params Config) *Oracle {
 		percent = 100
 	}
 	return &Oracle{
-		backend:     backend,
-		lastPrice:   params.Default,
-		checkBlocks: blocks,
-		maxEmpty:    blocks / 2,
-		maxBlocks:   blocks * 5,
-		percentile:  percent,
+		lastPrice:     config.Default,
+		checkBlocks:   blocks,
+		maxEmpty:      blocks / 2,
+		maxBlocks:     blocks * 5,
+		percentile:    percent,
+		chainConfig:   chainConfig,
+		getHeadHeader: getHeadHeader,
+		getBlock:      getBlock,
 	}
 }
 
@@ -80,7 +90,7 @@ func (gpo *Oracle) SuggestPrice(ctx context.Context) (*big.Int, error) {
 	lastPrice := gpo.lastPrice
 	gpo.cacheLock.RUnlock()
 
-	head, _ := gpo.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
+	head := gpo.getHeadHeader()
 	headHash := head.Hash()
 	if headHash == lastHead {
 		return lastPrice, nil
@@ -104,7 +114,7 @@ func (gpo *Oracle) SuggestPrice(ctx context.Context) (*big.Int, error) {
 	exp := 0
 	var blockPrices []*big.Int
 	for sent < gpo.checkBlocks && blockNum > 0 {
-		go gpo.getBlockPrices(ctx, types.MakeSigner(gpo.backend.ChainConfig(), big.NewInt(int64(blockNum))), blockNum, ch)
+		go gpo.getBlockPrices(ctx, types.MakeSigner(gpo.chainConfig, big.NewInt(int64(blockNum))), blockNum, ch)
 		sent++
 		exp++
 		blockNum--
@@ -125,7 +135,7 @@ func (gpo *Oracle) SuggestPrice(ctx context.Context) (*big.Int, error) {
 			continue
 		}
 		if blockNum > 0 && sent < gpo.maxBlocks {
-			go gpo.getBlockPrices(ctx, types.MakeSigner(gpo.backend.ChainConfig(), big.NewInt(int64(blockNum))), blockNum, ch)
+			go gpo.getBlockPrices(ctx, types.MakeSigner(gpo.chainConfig, big.NewInt(int64(blockNum))), blockNum, ch)
 			sent++
 			exp++
 			blockNum--
@@ -161,7 +171,7 @@ func (t transactionsByGasPrice) Less(i, j int) bool { return t[i].GasPrice().Cmp
 // getBlockPrices calculates the lowest transaction gas price in a given block
 // and sends it to the result channel. If the block is empty, price is nil.
 func (gpo *Oracle) getBlockPrices(ctx context.Context, signer types.Signer, blockNum uint64, ch chan getBlockPricesResult) {
-	block, err := gpo.backend.BlockByNumber(ctx, rpc.BlockNumber(blockNum))
+	block, err := gpo.getBlock(ctx, blockNum)
 	if block == nil {
 		ch <- getBlockPricesResult{nil, err}
 		return

eth/gasprice/gasprice_test.go

@@ -0,0 +1,99 @@
+// Copyright 2020 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 gasprice
+
+import (
+	"context"
+	"math"
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"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/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+type testBackend struct {
+	chain *core.BlockChain
+}
+
+func newTestBackend(t *testing.T) *testBackend {
+	var (
+		key, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		addr   = crypto.PubkeyToAddress(key.PublicKey)
+		gspec  = &core.Genesis{
+			Config: params.TestChainConfig,
+			Alloc:  core.GenesisAlloc{addr: {Balance: big.NewInt(math.MaxInt64)}},
+		}
+		signer = types.NewEIP155Signer(gspec.Config.ChainID)
+	)
+	engine := ethash.NewFaker()
+	db := rawdb.NewMemoryDatabase()
+	genesis, _ := gspec.Commit(db)
+
+	// Generate testing blocks
+	blocks, _ := core.GenerateChain(params.TestChainConfig, genesis, engine, db, 32, func(i int, b *core.BlockGen) {
+		b.SetCoinbase(common.Address{1})
+		tx, err := types.SignTx(types.NewTransaction(b.TxNonce(addr), common.HexToAddress("deadbeef"), big.NewInt(100), 21000, big.NewInt(int64(i)*params.GWei), nil), signer, key)
+		if err != nil {
+			t.Fatalf("failed to create tx: %v", err)
+		}
+		b.AddTx(tx)
+	})
+	// Construct testing chain
+	diskdb := rawdb.NewMemoryDatabase()
+	gspec.Commit(diskdb)
+	chain, err := core.NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{}, nil)
+	if err != nil {
+		t.Fatalf("Failed to create local chain, %v", err)
+	}
+	chain.InsertChain(blocks)
+	return &testBackend{chain: chain}
+}
+
+func (b *testBackend) CurrentHeader() *types.Header {
+	return b.chain.CurrentHeader()
+}
+
+func (b *testBackend) GetBlockByNumber(number uint64) *types.Block {
+	return b.chain.GetBlockByNumber(number)
+}
+
+func TestSuggestPrice(t *testing.T) {
+	config := Config{
+		Blocks:     3,
+		Percentile: 50,
+		Default:    big.NewInt(params.GWei),
+	}
+	backend := newTestBackend(t)
+	oracle := NewOracle(config, params.TestChainConfig, func() *types.Header { return backend.CurrentHeader() }, func(ctx context.Context, number uint64) (*types.Block, error) {
+		return backend.GetBlockByNumber(number), nil
+	})
+	got, err := oracle.SuggestPrice(context.Background())
+	if err != nil {
+		t.Fatalf("Failed to retrieve recommended gas price: %v", err)
+	}
+	expect := big.NewInt(params.GWei * int64(30))
+	if got.Cmp(expect) != 0 {
+		t.Fatalf("Gas price mismatch, want %d, got %d", expect, got)
+	}
+}

les/client.go

@@ -142,14 +142,11 @@ func New(ctx *node.ServiceContext, config *eth.Config) (*LightEthereum, error) {
 		leth.blockchain.SetHead(compat.RewindTo)
 		rawdb.WriteChainConfig(chainDb, genesisHash, chainConfig)
 	}
-
-	leth.ApiBackend = &LesApiBackend{ctx.ExtRPCEnabled(), leth, nil}
 	gpoParams := config.GPO
 	if gpoParams.Default == nil {
 		gpoParams.Default = config.Miner.GasPrice
 	}
-	leth.ApiBackend.gpo = gasprice.NewOracle(leth.ApiBackend, gpoParams)
-
+	leth.ApiBackend = &LesApiBackend{ctx.ExtRPCEnabled(), leth, gasprice.NewOracle(gpoParams, chainConfig, func() *types.Header { return leth.blockchain.CurrentHeader() }, leth.blockchain.GetBlockByNumber)}
 	return leth, nil
 }