eth, internal/cli: allow bor to run in snap sync (#1532)

This PR enables snap sync download mechanism. It allows users to use it as sync mode via setting the flag `syncmode` to `snap`. Snap sync instead of executing every block, downloads the state and chain from the p2p network trusting the peer(s) it's downloading from.

docs/cli/example_config.toml

@@ -13,7 +13,7 @@ ancient = ""                    # Data directory for ancient chain segments (def
 keystore = ""                   # Path of the directory where keystores are located
 "rpc.batchlimit" = 100          # Maximum number of messages in a batch (default=100, use 0 for no limits)
 "rpc.returndatalimit" = 100000  # Maximum size (in bytes) a result of an rpc request could have (default=100000, use 0 for no limits)
-syncmode = "full"               # Blockchain sync mode (only "full" sync supported)
+syncmode = "full"               # Blockchain sync mode ("full" or "snap")
 gcmode = "full"                 # Blockchain garbage collection mode ("full", "archive")
 snapshot = true                 # Enables the snapshot-database mode
 "bor.logs" = false              # Enables bor log retrieval

docs/cli/server.md

@@ -90,7 +90,7 @@ The ```bor server``` command runs the Bor client.
 
 - ```state.scheme```: Scheme to use for storing ethereum state ('hash' or 'path') (default: path)
 
-- ```syncmode```: Blockchain sync mode (only "full" sync supported) (default: full)
+- ```syncmode```: Blockchain sync mode ("full" or "snap") (default: full)
 
 - ```verbosity```: Logging verbosity for the server (5=trace|4=debug|3=info|2=warn|1=error|0=crit) (default: 3)
 

eth/handler.go

@@ -175,19 +175,14 @@ func newHandler(config *handlerConfig) (*handler, error) {
 		// * the last snap sync is not finished while user specifies a full sync this
 		//   time. But we don't have any recent state for full sync.
 		// In these cases however it's safe to reenable snap sync.
-
+		fullBlock, snapBlock := h.chain.CurrentBlock(), h.chain.CurrentSnapBlock()
-		// TODO - uncomment when we (Polygon-PoS, bor) have snap sync/pbss
+		if fullBlock.Number.Uint64() == 0 && snapBlock.Number.Uint64() > 0 {
-		// fullBlock, snapBlock := h.chain.CurrentBlock(), h.chain.CurrentSnapBlock()
+			h.snapSync.Store(true)
-
+			log.Warn("Switch sync mode from full sync to snap sync", "reason", "snap sync incomplete")
-		// TODO - uncomment when we (Polygon-PoS, bor) have snap sync/pbss
+		} else if !h.chain.HasState(fullBlock.Root) {
-		// For more info - https://github.com/ethereum/go-ethereum/pull/28171
+			h.snapSync.Store(true)
-		// if fullBlock.Number.Uint64() == 0 && snapBlock.Number.Uint64() > 0 {
+			log.Warn("Switch sync mode from full sync to snap sync", "reason", "head state missing")
-		// 	h.snapSync.Store(true)
+		}
-		// 	log.Warn("Switch sync mode from full sync to snap sync", "reason", "snap sync incomplete")
-		// } else if !h.chain.HasState(fullBlock.Root) {
-		// 	h.snapSync.Store(true)
-		// 	log.Warn("Switch sync mode from full sync to snap sync", "reason", "head state missing")
-		// }
 	} else {
 		head := h.chain.CurrentBlock()
 		if head.Number.Uint64() > 0 && h.chain.HasState(head.Root) {

eth/sync.go

@@ -201,43 +201,35 @@ func peerToSyncOp(mode downloader.SyncMode, p *eth.Peer) *chainSyncOp {
 }
 
 func (cs *chainSyncer) modeAndLocalHead() (downloader.SyncMode, *big.Int) {
-	// TODO - uncomment when we (Polygon-PoS, bor) have snap sync/pbss
+	// If we're in snap sync mode, return that directly
-	/*
+	if cs.handler.snapSync.Load() {
-		// If we're in snap sync mode, return that directly
+		block := cs.handler.chain.CurrentSnapBlock()
-		if cs.handler.snapSync.Load() {
+		td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
-			block := cs.handler.chain.CurrentSnapBlock()
+		return downloader.SnapSync, td
-			td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
+	}
-			return downloader.SnapSync, td
-		}
-	*/
 
 	// We are probably in full sync, but we might have rewound to before the
 	// snap sync pivot, check if we should re-enable snap sync.
 	head := cs.handler.chain.CurrentBlock()
-	// TODO - uncomment when we (Polygon-PoS, bor) have snap sync/pbss
+	if pivot := rawdb.ReadLastPivotNumber(cs.handler.database); pivot != nil {
-	/*
+		if head.Number.Uint64() < *pivot {
-		if pivot := rawdb.ReadLastPivotNumber(cs.handler.database); pivot != nil {
-			if head.Number.Uint64() < *pivot {
-				block := cs.handler.chain.CurrentSnapBlock()
-				td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
-				return downloader.SnapSync, td
-			}
-		}
-	*/
-
-	// TODO - uncomment when we (Polygon-PoS, bor) have snap sync/pbss
-	// For more info - https://github.com/ethereum/go-ethereum/pull/28171
-	/*
-		// We are in a full sync, but the associated head state is missing. To complete
-		// the head state, forcefully rerun the snap sync. Note it doesn't mean the
-		// persistent state is corrupted, just mismatch with the head block.
-		if !cs.handler.chain.HasState(head.Root) {
 			block := cs.handler.chain.CurrentSnapBlock()
 			td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
-			log.Info("Reenabled snap sync as chain is stateless")
 			return downloader.SnapSync, td
 		}
-	*/
+	}
+
+	// For more info - https://github.com/ethereum/go-ethereum/pull/28171
+	// We are in a full sync, but the associated head state is missing. To complete
+	// the head state, forcefully rerun the snap sync. Note it doesn't mean the
+	// persistent state is corrupted, just mismatch with the head block.
+	if !cs.handler.chain.HasState(head.Root) {
+		block := cs.handler.chain.CurrentSnapBlock()
+		td := cs.handler.chain.GetTd(block.Hash(), block.Number.Uint64())
+		log.Info("Reenabled snap sync as chain is stateless")
+		return downloader.SnapSync, td
+	}
+
 	// Nope, we're really full syncing
 	td := cs.handler.chain.GetTd(head.Hash(), head.Number.Uint64())
 

internal/cli/server/config.go

@@ -1161,10 +1161,7 @@ func (c *Config) buildEth(stack *node.Node, accountManager *accounts.Manager) (*
 	case "full":
 		n.SyncMode = downloader.FullSync
 	case "snap":
-		// n.SyncMode = downloader.SnapSync // TODO(snap): Uncomment when we have snap sync working
+		n.SyncMode = downloader.SnapSync
-		n.SyncMode = downloader.FullSync
-
-		log.Warn("Bor doesn't support Snap Sync yet, switching to Full Sync mode")
 	default:
 		return nil, fmt.Errorf("sync mode '%s' not found", c.SyncMode)
 	}

internal/cli/server/flags.go

@@ -88,7 +88,7 @@ func (c *Command) Flags(config *Config) *flagset.Flagset {
 	})
 	f.StringFlag(&flagset.StringFlag{
 		Name:    "syncmode",
-		Usage:   `Blockchain sync mode (only "full" sync supported)`,
+		Usage:   `Blockchain sync mode ("full" or "snap")`,
 		Value:   &c.cliConfig.SyncMode,
 		Default: c.cliConfig.SyncMode,
 	})