miner: recover state if parent is too old

miner/miner.go

@@ -35,10 +35,12 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 )
 
-// Backend wraps all methods required for mining.
+// Backend wraps all methods required for mining. Only full node is capable
+// to offer all the functions here.
 type Backend interface {
 	BlockChain() *core.BlockChain
 	TxPool() *core.TxPool
+	StateAtBlock(block *types.Block, reexec uint64, base *state.StateDB, checkLive bool, preferDisk bool) (statedb *state.StateDB, err error)
 }
 
 // Config is the configuration parameters of mining.

miner/worker.go

@@ -749,11 +749,17 @@ func (w *worker) resultLoop() {
 // makeEnv creates a new environment for the sealing block.
 func (w *worker) makeEnv(parent *types.Block, header *types.Header, coinbase common.Address) (*environment, error) {
 	// Retrieve the parent state to execute on top and start a prefetcher for
-	// the miner to speed block sealing up a bit. Note since the sealing block
-	// can be created upon the arbitrary parent block, but the state of parent
-	// block may already be pruned, so the necessary state recovery is needed
-	// here in the future. TODO(rjl493456442).
+	// the miner to speed block sealing up a bit.
 	state, err := w.chain.StateAt(parent.Root())
+	if err != nil {
+		// Note since the sealing block can be created upon the arbitrary parent
+		// block, but the state of parent block may already be pruned, so the necessary
+		// state recovery is needed here in the future.
+		//
+		// The maximum acceptable reorg depth can be limited by the finalised block
+		// somehow. TODO(rjl493456442) fix the hard-coded number here later.
+		state, err = w.eth.StateAtBlock(parent, 1024, nil, false, false)
+	}
 	if err != nil {
 		return nil, err
 	}