Re-add GPO creation in backend

Clique consensus requires a GPO to function.

Author: bts

eth/backend.go

@@ -40,6 +40,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth/downloader"
 	"github.com/ethereum/go-ethereum/eth/filters"
+	"github.com/ethereum/go-ethereum/eth/gasprice"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
@@ -180,6 +181,11 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 	eth.miner.SetExtra(makeExtraData(config.ExtraData, eth.chainConfig.IsQuorum))
 
 	eth.ApiBackend = &EthApiBackend{eth, nil}
+	gpoParams := config.GPO
+	if gpoParams.Default == nil {
+		gpoParams.Default = config.GasPrice
+	}
+	eth.ApiBackend.gpo = gasprice.NewOracle(eth.ApiBackend, gpoParams)
 
 	return eth, nil
 }