refactor genesis state flag handling, support url (#10449)

* refactor genesis state flag handling, support url

* lint fix

Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>
Co-authored-by: Raul Jordan <raul@prysmaticlabs.com>

cmd/beacon-chain/BUILD.bazel

@@ -22,6 +22,7 @@ go_library(
         "//cmd/beacon-chain/flags:go_default_library",
         "//cmd/beacon-chain/powchain:go_default_library",
         "//cmd/beacon-chain/sync/checkpoint:go_default_library",
+        "//cmd/beacon-chain/sync/genesis:go_default_library",
         "//config/features:go_default_library",
         "//io/file:go_default_library",
         "//io/logs:go_default_library",

cmd/beacon-chain/flags/base.go

@@ -191,12 +191,6 @@ var (
 		Usage: "Sets the maximum number of headers that a deposit log query can fetch.",
 		Value: uint64(1000),
 	}
-	// GenesisStatePath defines a flag to start the beacon chain from a give genesis state file.
-	GenesisStatePath = &cli.StringFlag{
-		Name: "genesis-state",
-		Usage: "Load a genesis state from ssz file. Testnet genesis files can be found in the " +
-			"eth2-clients/eth2-testnets repository on github.",
-	}
 	// WeakSubjectivityCheckpoint defines the weak subjectivity checkpoint the node must sync through to defend against long range attacks.
 	WeakSubjectivityCheckpoint = &cli.StringFlag{
 		Name: "weak-subjectivity-checkpoint",

cmd/beacon-chain/main.go

@@ -18,6 +18,7 @@ import (
 	"github.com/prysmaticlabs/prysm/cmd/beacon-chain/flags"
 	powchaincmd "github.com/prysmaticlabs/prysm/cmd/beacon-chain/powchain"
 	"github.com/prysmaticlabs/prysm/cmd/beacon-chain/sync/checkpoint"
+	"github.com/prysmaticlabs/prysm/cmd/beacon-chain/sync/genesis"
 	"github.com/prysmaticlabs/prysm/config/features"
 	"github.com/prysmaticlabs/prysm/io/file"
 	"github.com/prysmaticlabs/prysm/io/logs"
@@ -65,7 +66,6 @@ var appFlags = []cli.Flag{
 	flags.NetworkID,
 	flags.WeakSubjectivityCheckpoint,
 	flags.Eth1HeaderReqLimit,
-	flags.GenesisStatePath,
 	flags.MinPeersPerSubnet,
 	flags.SuggestedFeeRecipient,
 	cmd.EnableBackupWebhookFlag,
@@ -122,6 +122,8 @@ var appFlags = []cli.Flag{
 	checkpoint.BlockPath,
 	checkpoint.StatePath,
 	checkpoint.RemoteURL,
+	genesis.StatePath,
+	genesis.BeaconAPIURL,
 }
 
 func init() {
@@ -246,13 +248,21 @@ func startNode(ctx *cli.Context) error {
 		node.WithBlockchainFlagOptions(blockchainFlagOpts),
 		node.WithPowchainFlagOptions(powchainFlagOpts),
 	}
-	cptOpts, err := checkpoint.BeaconNodeOptions(ctx)
-	if err != nil {
-		return err
+
+	optFuncs := []func(*cli.Context) (node.Option, error){
+		genesis.BeaconNodeOptions,
+		checkpoint.BeaconNodeOptions,
 	}
-	if cptOpts != nil {
-		opts = append(opts, cptOpts)
+	for _, of := range optFuncs {
+		ofo, err := of(ctx)
+		if err != nil {
+			return err
+		}
+		if ofo != nil {
+			opts = append(opts, ofo)
+		}
 	}
+
 	beacon, err := node.New(ctx, opts...)
 	if err != nil {
 		return err

cmd/beacon-chain/sync/genesis/BUILD.bazel

@@ -0,0 +1,14 @@
+load("@prysm//tools/go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["options.go"],
+    importpath = "github.com/prysmaticlabs/prysm/cmd/beacon-chain/sync/genesis",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//beacon-chain/node:go_default_library",
+        "//beacon-chain/sync/genesis:go_default_library",
+        "@com_github_pkg_errors//:go_default_library",
+        "@com_github_urfave_cli_v2//:go_default_library",
+    ],
+)

cmd/beacon-chain/sync/genesis/options.go

@@ -0,0 +1,53 @@
+package genesis
+
+import (
+	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/beacon-chain/node"
+	"github.com/prysmaticlabs/prysm/beacon-chain/sync/genesis"
+	"github.com/urfave/cli/v2"
+)
+
+var (
+	// StatePath defines a flag to start the beacon chain from a give genesis state file.
+	StatePath = &cli.PathFlag{
+		Name: "genesis-state",
+		Usage: "Load a genesis state from ssz file. Testnet genesis files can be found in the " +
+			"eth2-clients/eth2-testnets repository on github.",
+	}
+	BeaconAPIURL = &cli.StringFlag{
+		Name: "genesis-beacon-api-url",
+		Usage: "URL of a synced beacon node to trust for obtaining genesis state. " +
+			"As an additional safety measure, it is strongly recommended to only use this option in conjunction with " +
+			"--weak-subjectivity-checkpoint flag",
+	}
+)
+
+// BeaconNodeOptions is responsible for determining if the checkpoint sync options have been used, and if so,
+// reading the block and state ssz-serialized values from the filesystem locations specified and preparing a
+// checkpoint.Initializer, which uses the provided io.ReadClosers to initialize the beacon node database.
+func BeaconNodeOptions(c *cli.Context) (node.Option, error) {
+	statePath := c.Path(StatePath.Name)
+	remoteURL := c.String(BeaconAPIURL.Name)
+	if remoteURL != "" {
+		return func(node *node.BeaconNode) error {
+			var err error
+			node.GenesisInitializer, err = genesis.NewAPIInitializer(remoteURL)
+			if err != nil {
+				return errors.Wrap(err, "error constructing beacon node api client for genesis state init")
+			}
+			return nil
+		}, nil
+	}
+
+	if statePath == "" {
+		return nil, nil
+	}
+
+	return func(node *node.BeaconNode) (err error) {
+		node.GenesisInitializer, err = genesis.NewFileInitializer(statePath)
+		if err != nil {
+			return errors.Wrap(err, "error preparing to initialize genesis db state from local ssz files")
+		}
+		return nil
+	}, nil
+}

cmd/beacon-chain/usage.go

@@ -8,6 +8,7 @@ import (
 	"github.com/prysmaticlabs/prysm/cmd"
 	"github.com/prysmaticlabs/prysm/cmd/beacon-chain/flags"
 	"github.com/prysmaticlabs/prysm/cmd/beacon-chain/sync/checkpoint"
+	"github.com/prysmaticlabs/prysm/cmd/beacon-chain/sync/genesis"
 	"github.com/prysmaticlabs/prysm/config/features"
 	"github.com/prysmaticlabs/prysm/runtime/debug"
 	"github.com/urfave/cli/v2"
@@ -76,9 +77,6 @@ var appHelpFlagGroups = []flagGroup{
 			cmd.BoltMMapInitialSizeFlag,
 			cmd.ValidatorMonitorIndicesFlag,
 			cmd.ApiTimeoutFlag,
-			checkpoint.BlockPath,
-			checkpoint.StatePath,
-			checkpoint.RemoteURL,
 		},
 	},
 	{
@@ -127,8 +125,12 @@ var appHelpFlagGroups = []flagGroup{
 			flags.NetworkID,
 			flags.WeakSubjectivityCheckpoint,
 			flags.Eth1HeaderReqLimit,
-			flags.GenesisStatePath,
 			flags.MinPeersPerSubnet,
+			checkpoint.BlockPath,
+			checkpoint.StatePath,
+			checkpoint.RemoteURL,
+			genesis.StatePath,
+			genesis.BeaconAPIURL,
 		},
 	},
 	{