miner: suspend miner if node is syncing (ethereum#27218)

Drop the notions of uncles, and disables activities while syncing

-  Disable activities (e.g. generate pending state) while node is syncing,
-  Disable empty block submission (but empty block is still kept for payload building),
-  Drop uncle notion since (ethash is already deprecated)

eth/api_backend.go

@@ -68,6 +68,9 @@ func (b *EthAPIBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumb
 	// Pending block is only known by the miner
 	if number == rpc.PendingBlockNumber {
 		block := b.eth.miner.PendingBlock()
+		if block == nil {
+			return nil, errors.New("pending block is not available")
+		}
 		return block.Header(), nil
 	}
 	// Otherwise resolve and return the block
@@ -122,6 +125,9 @@ func (b *EthAPIBackend) BlockByNumber(ctx context.Context, number rpc.BlockNumbe
 	// Pending block is only known by the miner
 	if number == rpc.PendingBlockNumber {
 		block := b.eth.miner.PendingBlock()
+		if block == nil {
+			return nil, errors.New("pending block is not available")
+		}
 		return block, nil
 	}
 	// Otherwise resolve and return the block
@@ -196,6 +202,9 @@ func (b *EthAPIBackend) StateAndHeaderByNumber(ctx context.Context, number rpc.B
 	// Pending state is only known by the miner
 	if number == rpc.PendingBlockNumber {
 		block, state := b.eth.miner.Pending()
+		if block == nil || state == nil {
+			return nil, nil, errors.New("pending state is not available")
+		}
 		return state, block.Header(), nil
 	}
 	// Otherwise resolve the block number and return its state

eth/api_debug.go

@@ -56,6 +56,9 @@ func (api *DebugAPI) DumpBlock(blockNr rpc.BlockNumber) (state.Dump, error) {
 		// both the pending block as well as the pending state from
 		// the miner and operate on those
 		_, stateDb := api.eth.miner.Pending()
+		if stateDb == nil {
+			return state.Dump{}, errors.New("pending state is not available")
+		}
 		return stateDb.RawDump(opts), nil
 	}
 	var header *types.Header
@@ -141,6 +144,9 @@ func (api *DebugAPI) AccountRange(blockNrOrHash rpc.BlockNumberOrHash, start hex
 			// both the pending block as well as the pending state from
 			// the miner and operate on those
 			_, stateDb = api.eth.miner.Pending()
+			if stateDb == nil {
+				return state.IteratorDump{}, errors.New("pending state is not available")
+			}
 		} else {
 			var header *types.Header
 			if number == rpc.LatestBlockNumber {

eth/filters/filter.go

@@ -334,7 +334,7 @@ func (f *Filter) checkMatches(ctx context.Context, header *types.Header) ([]*typ
 // pendingLogs returns the logs matching the filter criteria within the pending block.
 func (f *Filter) pendingLogs() []*types.Log {
 	block, receipts := f.sys.backend.PendingBlockAndReceipts()
-	if block == nil {
+	if block == nil || receipts == nil {
 		return nil
 	}
 	if bloomFilter(block.Bloom(), f.addresses, f.topics) {

miner/miner.go

@@ -131,16 +131,22 @@ func (miner *Miner) update() {
 					shouldStart = true
 					log.Info("Mining aborted due to sync")
 				}
+				miner.worker.syncing.Store(true)
+
 			case downloader.FailedEvent:
 				canStart = true
 				if shouldStart {
 					miner.worker.start()
 				}
+				miner.worker.syncing.Store(false)
+
 			case downloader.DoneEvent:
 				canStart = true
 				if shouldStart {
 					miner.worker.start()
 				}
+				miner.worker.syncing.Store(false)
+
 				// Stop reacting to downloader events
 				events.Unsubscribe()
 			}
@@ -196,12 +202,14 @@ func (miner *Miner) SetRecommitInterval(interval time.Duration) {
 	miner.worker.setRecommitInterval(interval)
 }
 
-// Pending returns the currently pending block and associated state.
+// Pending returns the currently pending block and associated state. The returned
+// values can be nil in case the pending block is not initialized
 func (miner *Miner) Pending() (*types.Block, *state.StateDB) {
 	return miner.worker.pending()
 }
 
-// PendingBlock returns the currently pending block.
+// PendingBlock returns the currently pending block. The returned block can be
+// nil in case the pending block is not initialized.
 //
 // Note, to access both the pending block and the pending state
 // simultaneously, please use Pending(), as the pending state can
@@ -211,6 +219,7 @@ func (miner *Miner) PendingBlock() *types.Block {
 }
 
 // PendingBlockAndReceipts returns the currently pending block and corresponding receipts.
+// The returned values can be nil in case the pending block is not initialized.
 func (miner *Miner) PendingBlockAndReceipts() (*types.Block, types.Receipts) {
 	return miner.worker.pendingBlockAndReceipts()
 }
@@ -225,23 +234,6 @@ func (miner *Miner) SetGasCeil(ceil uint64) {
 	miner.worker.setGasCeil(ceil)
 }
 
-// EnablePreseal turns on the preseal mining feature. It's enabled by default.
-// Note this function shouldn't be exposed to API, it's unnecessary for users
-// (miners) to actually know the underlying detail. It's only for outside project
-// which uses this library.
-func (miner *Miner) EnablePreseal() {
-	miner.worker.enablePreseal()
-}
-
-// DisablePreseal turns off the preseal mining feature. It's necessary for some
-// fake consensus engine which can seal blocks instantaneously.
-// Note this function shouldn't be exposed to API, it's unnecessary for users
-// (miners) to actually know the underlying detail. It's only for outside project
-// which uses this library.
-func (miner *Miner) DisablePreseal() {
-	miner.worker.disablePreseal()
-}
-
 // SubscribePendingLogs starts delivering logs from pending transactions
 // to the given channel.
 func (miner *Miner) SubscribePendingLogs(ch chan<- []*types.Log) event.Subscription {