eth, internal/web3ext: admin flag to allow reenabling fast sync

eth/api.go

@@ -25,6 +25,8 @@ import (
 	"math/big"
 	"os"
 	"runtime"
+	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/ethash"
@@ -275,6 +277,23 @@ func (api *PrivateAdminAPI) ImportChain(file string) (bool, error) {
 	return true, nil
 }
 
+// FastSync reenables fast sync for a shot shot sync round. Use with extreme caution.
+func (api *PrivateAdminAPI) FastSync() {
+	// Create a diplaimer warning message for the user
+	message1 := fmt.Sprintf("Re-enabling fast sync. If you don't know what this means, quit now!")
+	message2 := fmt.Sprintf("After fast sync completes, check eth.getBlock('latest') against an explorer!")
+	separator := strings.Repeat("-", len(message2))
+
+	glog.V(logger.Warn).Info(separator)
+	glog.V(logger.Warn).Info(message1)
+	glog.V(logger.Warn).Info(message2)
+	glog.V(logger.Warn).Info(separator)
+
+	// Reenable fast sync and abort any currently running sync cycle
+	atomic.StoreUint32(&api.eth.protocolManager.fastSync, 1)
+	api.eth.protocolManager.downloader.Cancel()
+}
+
 // PublicDebugAPI is the collection of Etheruem full node APIs exposed
 // over the public debugging endpoint.
 type PublicDebugAPI struct {

eth/downloader/downloader.go

@@ -277,7 +277,7 @@ func (d *Downloader) UnregisterPeer(id string) error {
 	d.cancelLock.RUnlock()
 
 	if master {
-		d.cancel()
+		d.Cancel()
 	}
 	return nil
 }
@@ -357,7 +357,7 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int, mode
 	d.cancelPeer = id
 	d.cancelLock.Unlock()
 
-	defer d.cancel() // No matter what, we can't leave the cancel channel open
+	defer d.Cancel() // No matter what, we can't leave the cancel channel open
 
 	// Set the requested sync mode, unless it's forbidden
 	d.mode = mode
@@ -478,14 +478,13 @@ func (d *Downloader) spawnSync(origin uint64, fetchers ...func() error) error {
 		}
 	}
 	d.queue.Close()
-	d.cancel()
+	d.Cancel()
 	wg.Wait()
 	return err
 }
 
-// cancel cancels all of the operations and resets the queue. It returns true
+// Cancel cancels all of the operations and resets the queue.
-// if the cancel operation was completed.
+func (d *Downloader) Cancel() {
-func (d *Downloader) cancel() {
 	// Close the current cancel channel
 	d.cancelLock.Lock()
 	if d.cancelCh != nil {
@@ -512,7 +511,7 @@ func (d *Downloader) Terminate() {
 	d.quitLock.Unlock()
 
 	// Cancel any pending download requests
-	d.cancel()
+	d.Cancel()
 }
 
 // fetchHeight retrieves the head header of the remote peer to aid in estimating
@@ -935,7 +934,7 @@ func (d *Downloader) fetchNodeData() error {
 				if err != nil {
 					// If the node data processing failed, the root hash is very wrong, abort
 					glog.V(logger.Error).Infof("peer %d: state processing failed: %v", packet.PeerId(), err)
-					d.cancel()
+					d.Cancel()
 					return
 				}
 				// Processing succeeded, notify state fetcher of continuation

eth/downloader/downloader_test.go

@@ -974,7 +974,7 @@ func testCancel(t *testing.T, protocol int, mode SyncMode) {
 	tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)
 
 	// Make sure canceling works with a pristine downloader
-	tester.downloader.cancel()
+	tester.downloader.Cancel()
 	if !tester.downloader.queue.Idle() {
 		t.Errorf("download queue not idle")
 	}
@@ -982,7 +982,7 @@ func testCancel(t *testing.T, protocol int, mode SyncMode) {
 	if err := tester.sync("peer", nil, mode); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
-	tester.downloader.cancel()
+	tester.downloader.Cancel()
 	if !tester.downloader.queue.Idle() {
 		t.Errorf("download queue not idle")
 	}

internal/web3ext/web3ext.go

@@ -197,6 +197,11 @@ web3._extend({
 			call: 'admin_importChain',
 			params: 1
 		}),
+		new web3._extend.Method({
+			name: 'fastSync',
+			call: 'admin_fastSync',
+			params: 0
+		}),
 		new web3._extend.Method({
 			name: 'sleepBlocks',
 			call: 'admin_sleepBlocks',