Add Flag For Minimum Handshakes (#4280)

* add flag
* jim and preston's review
* check max peers
* gaz
* Merge branch 'master' of https://github.com/prysmaticlabs/geth-sharding into minStatusCount
* remove space
* add references
* add warning log
* change log
* gaz

beacon-chain/flags/BUILD.bazel

@@ -10,5 +10,9 @@ go_library(
     ],
     importpath = "github.com/prysmaticlabs/prysm/beacon-chain/flags",
     visibility = ["//beacon-chain:__subpackages__"],
-    deps = ["@com_github_urfave_cli//:go_default_library"],
+    deps = [
+        "//shared/cmd:go_default_library",
+        "@com_github_sirupsen_logrus//:go_default_library",
+        "@com_github_urfave_cli//:go_default_library",
+    ],
 )

beacon-chain/flags/base.go

@@ -48,4 +48,12 @@ var (
 		Name:  "grpc-gateway-port",
 		Usage: "Enable gRPC gateway for JSON requests",
 	}
+
+	// MinSyncPeers specifies the required number of successful peer handshakes in order
+	// to start syncing with external peers.
+	MinSyncPeers = cli.IntFlag{
+		Name:  "min-sync-peers",
+		Usage: "The required number of valid peers to connect with before syncing.",
+		Value: 3,
+	}
 )

beacon-chain/flags/config.go

@@ -1,6 +1,8 @@
 package flags
 
 import (
+	"github.com/prysmaticlabs/prysm/shared/cmd"
+	log "github.com/sirupsen/logrus"
 	"github.com/urfave/cli"
 )
 
@@ -11,6 +13,7 @@ type GlobalFlags struct {
 	EnableArchivedValidatorSetChanges bool
 	EnableArchivedBlocks              bool
 	EnableArchivedAttestations        bool
+	MinimumSyncPeers                  int
 }
 
 var globalConfig *GlobalFlags
@@ -44,5 +47,16 @@ func ConfigureGlobalFlags(ctx *cli.Context) {
 	if ctx.GlobalBool(ArchiveAttestationsFlag.Name) {
 		cfg.EnableArchivedAttestations = true
 	}
+	configureMinimumPeers(ctx, cfg)
+
 	Init(cfg)
 }
+
+func configureMinimumPeers(ctx *cli.Context, cfg *GlobalFlags) {
+	cfg.MinimumSyncPeers = ctx.GlobalInt(MinSyncPeers.Name)
+	maxPeers := int(ctx.GlobalInt64(cmd.P2PMaxPeers.Name))
+	if cfg.MinimumSyncPeers > maxPeers {
+		log.Warnf("Changing Minimum Sync Peers to %d", maxPeers)
+		cfg.MinimumSyncPeers = maxPeers
+	}
+}

beacon-chain/main.go

@@ -32,6 +32,7 @@ var appFlags = []cli.Flag{
 	flags.CertFlag,
 	flags.KeyFlag,
 	flags.GRPCGatewayPort,
+	flags.MinSyncPeers,
 	flags.InteropMockEth1DataVotesFlag,
 	flags.InteropGenesisStateFlag,
 	flags.InteropNumValidatorsFlag,

beacon-chain/sync/initial-sync/BUILD.bazel

@@ -15,6 +15,7 @@ go_library(
         "//beacon-chain/core/feed/state:go_default_library",
         "//beacon-chain/core/helpers:go_default_library",
         "//beacon-chain/db:go_default_library",
+        "//beacon-chain/flags:go_default_library",
         "//beacon-chain/p2p:go_default_library",
         "//beacon-chain/sync:go_default_library",
         "//proto/beacon/p2p/v1:go_default_library",

beacon-chain/sync/initial-sync/service.go

@@ -11,6 +11,7 @@ import (
 	statefeed "github.com/prysmaticlabs/prysm/beacon-chain/core/feed/state"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/beacon-chain/db"
+	"github.com/prysmaticlabs/prysm/beacon-chain/flags"
 	"github.com/prysmaticlabs/prysm/beacon-chain/p2p"
 	"github.com/prysmaticlabs/prysm/shared"
 	"github.com/prysmaticlabs/prysm/shared/params"
@@ -25,7 +26,6 @@ type blockchainService interface {
 }
 
 const (
-	minStatusCount           = 3               // TODO(3147): Set this to more than 3, maybe configure from flag?
 	handshakePollingInterval = 5 * time.Second // Polling interval for checking the number of received handshakes.
 )
 
@@ -118,12 +118,12 @@ func (s *InitialSync) Start() {
 	// Every 5 sec, report handshake count.
 	for {
 		count := len(s.p2p.Peers().Connected())
-		if count >= minStatusCount {
+		if count >= flags.Get().MinimumSyncPeers {
 			break
 		}
 		log.WithField(
 			"handshakes",
-			fmt.Sprintf("%d/%d", count, minStatusCount),
+			fmt.Sprintf("%d/%d", count, flags.Get().MinimumSyncPeers),
 		).Info("Waiting for enough peer handshakes before syncing")
 		time.Sleep(handshakePollingInterval)
 	}

beacon-chain/usage.go

@@ -98,6 +98,7 @@ var appHelpFlagGroups = []flagGroup{
 			cmd.StaticPeers,
 			cmd.EnableUPnPFlag,
 			cmd.P2PEncoding,
+			flags.MinSyncPeers,
 		},
 	},
 	{