op-node: Support multiple beacon archiver/fallbacks (#10655)

* op-node: Support multiple beacon archiver/fallbacks

* op-node: rename flag to l1.beacon-fallbacks

- retain old flag name and env var
- fix some tests

* Update op-node/node/client_test.go
Co-authored-by: Adrian Sutton <adrian@oplabs.co>

---------
Co-authored-by: Adrian Sutton <adrian@oplabs.co>

op-node/flags/flags.go

@@ -34,8 +34,12 @@ func init() {
 	cli.VersionFlag.(*cli.BoolFlag).Category = MiscCategory
 }
 
-func prefixEnvVars(name string) []string {
-	return []string{EnvVarPrefix + "_" + name}
+func prefixEnvVars(names ...string) []string {
+	envs := make([]string, 0, len(names))
+	for _, name := range names {
+		envs = append(envs, EnvVarPrefix+"_"+name)
+	}
+	return envs
 }
 
 var (
@@ -76,11 +80,11 @@ var (
 		EnvVars:  prefixEnvVars("L1_BEACON_HEADER"),
 		Category: L1RPCCategory,
 	}
-	BeaconArchiverAddr = &cli.StringFlag{
-		Name:     "l1.beacon-archiver",
-		Usage:    "Address of L1 Beacon-node compatible HTTP endpoint to use. This is used to fetch blobs that the --l1.beacon does not have (i.e expired blobs).",
-		Required: false,
-		EnvVars:  prefixEnvVars("L1_BEACON_ARCHIVER"),
+	BeaconFallbackAddrs = &cli.StringSliceFlag{
+		Name:     "l1.beacon-fallbacks",
+		Aliases:  []string{"l1.beacon-archiver"},
+		Usage:    "Addresses of L1 Beacon-API compatible HTTP fallback endpoints. Used to fetch blob sidecars not availalbe at the l1.beacon (e.g. expired blobs).",
+		EnvVars:  prefixEnvVars("L1_BEACON_FALLBACKS", "L1_BEACON_ARCHIVER"),
 		Category: L1RPCCategory,
 	}
 	BeaconCheckIgnore = &cli.BoolFlag{
@@ -364,7 +368,7 @@ var requiredFlags = []cli.Flag{
 var optionalFlags = []cli.Flag{
 	BeaconAddr,
 	BeaconHeader,
-	BeaconArchiverAddr,
+	BeaconFallbackAddrs,
 	BeaconCheckIgnore,
 	BeaconFetchAllSidecars,
 	SyncModeFlag,

op-node/flags/flags_test.go

@@ -61,7 +61,6 @@ func TestDeprecatedFlagsAreHidden(t *testing.T) {
 		flagName := flag.Names()[0]
 
 		t.Run(flagName, func(t *testing.T) {
-
 			visibleFlag, ok := flag.(interface {
 				IsVisible() bool
 			})
@@ -72,6 +71,11 @@ func TestDeprecatedFlagsAreHidden(t *testing.T) {
 }
 
 func TestHasEnvVar(t *testing.T) {
+	// known exceptions to the number of env vars
+	expEnvVars := map[string]int{
+		BeaconFallbackAddrs.Name: 2,
+	}
+
 	for _, flag := range Flags {
 		flag := flag
 		flagName := flag.Names()[0]
@@ -83,39 +87,43 @@ func TestHasEnvVar(t *testing.T) {
 			envFlagGetter, ok := flag.(interface {
 				GetEnvVars() []string
 			})
-			envFlags := envFlagGetter.GetEnvVars()
 			require.True(t, ok, "must be able to cast the flag to an EnvVar interface")
-			require.Equal(t, 1, len(envFlags), "flags should have exactly one env var")
+			envFlags := envFlagGetter.GetEnvVars()
+			if numEnvVars, ok := expEnvVars[flagName]; ok {
+				require.Equalf(t, numEnvVars, len(envFlags), "flags should have %d env vars", numEnvVars)
+			} else {
+				require.Equal(t, 1, len(envFlags), "flags should have exactly one env var")
+			}
 		})
 	}
 }
 
 func TestEnvVarFormat(t *testing.T) {
+	skippedFlags := []string{
+		L1NodeAddr.Name,
+		L2EngineAddr.Name,
+		L2EngineJWTSecret.Name,
+		L1TrustRPC.Name,
+		L1RPCProviderKind.Name,
+		SnapshotLog.Name,
+		BackupL2UnsafeSyncRPC.Name,
+		BackupL2UnsafeSyncRPCTrustRPC.Name,
+		"p2p.scoring",
+		"p2p.ban.peers",
+		"p2p.ban.threshold",
+		"p2p.ban.duration",
+		"p2p.listen.tcp",
+		"p2p.listen.udp",
+		"p2p.useragent",
+		"p2p.gossip.mesh.lo",
+		"p2p.gossip.mesh.floodpublish",
+		"l2.engine-sync",
+	}
+
 	for _, flag := range Flags {
 		flag := flag
 		flagName := flag.Names()[0]
 
-		skippedFlags := []string{
-			L1NodeAddr.Name,
-			L2EngineAddr.Name,
-			L2EngineJWTSecret.Name,
-			L1TrustRPC.Name,
-			L1RPCProviderKind.Name,
-			SnapshotLog.Name,
-			BackupL2UnsafeSyncRPC.Name,
-			BackupL2UnsafeSyncRPCTrustRPC.Name,
-			"p2p.scoring",
-			"p2p.ban.peers",
-			"p2p.ban.threshold",
-			"p2p.ban.duration",
-			"p2p.listen.tcp",
-			"p2p.listen.udp",
-			"p2p.useragent",
-			"p2p.gossip.mesh.lo",
-			"p2p.gossip.mesh.floodpublish",
-			"l2.engine-sync",
-		}
-
 		t.Run(flagName, func(t *testing.T) {
 			if slices.Contains(skippedFlags, flagName) {
 				t.Skipf("Skipping flag %v which is known to not have a standard flag name <-> env var conversion", flagName)
@@ -126,9 +134,8 @@ func TestEnvVarFormat(t *testing.T) {
 			envFlagGetter, ok := flag.(interface {
 				GetEnvVars() []string
 			})
-			envFlags := envFlagGetter.GetEnvVars()
 			require.True(t, ok, "must be able to cast the flag to an EnvVar interface")
-			require.Equal(t, 1, len(envFlags), "flags should have exactly one env var")
+			envFlags := envFlagGetter.GetEnvVars()
 			expectedEnvVar := opservice.FlagNameToEnvVarName(flagName, "OP_NODE")
 			require.Equal(t, expectedEnvVar, envFlags[0])
 		})

op-node/node/client.go

@@ -178,11 +178,11 @@ func (cfg *PreparedL1Endpoint) Check() error {
 }
 
 type L1BeaconEndpointConfig struct {
-	BeaconAddr             string // Address of L1 User Beacon-API endpoint to use (beacon namespace required)
-	BeaconHeader           string // Optional HTTP header for all requests to L1 Beacon
-	BeaconArchiverAddr     string // Address of L1 User Beacon-API Archive endpoint to use for expired blobs (beacon namespace required)
-	BeaconCheckIgnore      bool   // When false, halt startup if the beacon version endpoint fails
-	BeaconFetchAllSidecars bool   // Whether to fetch all blob sidecars and filter locally
+	BeaconAddr             string   // Address of L1 User Beacon-API endpoint to use (beacon namespace required)
+	BeaconHeader           string   // Optional HTTP header for all requests to L1 Beacon
+	BeaconFallbackAddrs    []string // Addresses of L1 Beacon-API fallback endpoints (only for blob sidecars retrieval)
+	BeaconCheckIgnore      bool     // When false, halt startup if the beacon version endpoint fails
+	BeaconFetchAllSidecars bool     // Whether to fetch all blob sidecars and filter locally
 }
 
 var _ L1BeaconEndpointSetup = (*L1BeaconEndpointConfig)(nil)
@@ -197,11 +197,12 @@ func (cfg *L1BeaconEndpointConfig) Setup(ctx context.Context, log log.Logger) (c
 		opts = append(opts, client.WithHeader(hdr))
 	}
 
-	a := client.NewBasicHTTPClient(cfg.BeaconAddr, log, opts...)
-	if cfg.BeaconArchiverAddr != "" {
-		b := client.NewBasicHTTPClient(cfg.BeaconArchiverAddr, log)
+	for _, addr := range cfg.BeaconFallbackAddrs {
+		b := client.NewBasicHTTPClient(addr, log)
 		fb = append(fb, sources.NewBeaconHTTPClient(b))
 	}
+
+	a := client.NewBasicHTTPClient(cfg.BeaconAddr, log, opts...)
 	return sources.NewBeaconHTTPClient(a), fb, nil
 }
 

op-node/node/client_test.go

 package node
 
 import (
+	"context"
 	"net/http"
 	"testing"
 
@@ -60,3 +61,32 @@ func TestParseHTTPHeader(t *testing.T) {
 		})
 	}
 }
+
+func TestL1BeaconEndpointConfig_Setup(t *testing.T) {
+	for _, test := range []struct {
+		desc string
+		baa  []string
+		len  int
+	}{
+		{
+			desc: "empty",
+		},
+		{
+			desc: "one",
+			baa:  []string{"http://foo.bar"},
+			len:  1,
+		},
+		{
+			desc: "three",
+			baa:  []string{"http://foo.bar", "http://op.ti", "http://ba.se"},
+			len:  3,
+		},
+	} {
+		t.Run(test.desc, func(t *testing.T) {
+			cfg := L1BeaconEndpointConfig{BeaconFallbackAddrs: test.baa}
+			_, fb, err := cfg.Setup(context.Background(), nil)
+			require.NoError(t, err)
+			require.Len(t, fb, test.len)
+		})
+	}
+}

op-node/service.go

@@ -132,7 +132,7 @@ func NewBeaconEndpointConfig(ctx *cli.Context) node.L1BeaconEndpointSetup {
 	return &node.L1BeaconEndpointConfig{
 		BeaconAddr:             ctx.String(flags.BeaconAddr.Name),
 		BeaconHeader:           ctx.String(flags.BeaconHeader.Name),
-		BeaconArchiverAddr:     ctx.String(flags.BeaconArchiverAddr.Name),
+		BeaconFallbackAddrs:    ctx.StringSlice(flags.BeaconFallbackAddrs.Name),
 		BeaconCheckIgnore:      ctx.Bool(flags.BeaconCheckIgnore.Name),
 		BeaconFetchAllSidecars: ctx.Bool(flags.BeaconFetchAllSidecars.Name),
 	}

op-service/sources/l1_beacon_client.go

@@ -179,8 +179,9 @@ func NewL1BeaconClient(cl BeaconClient, cfg L1BeaconClientConfig, fallbacks ...B
 	cs := append([]BlobSideCarsFetcher{cl}, fallbacks...)
 	return &L1BeaconClient{
 		cl:   cl,
-		pool: NewClientPool[BlobSideCarsFetcher](cs...),
-		cfg:  cfg}
+		pool: NewClientPool(cs...),
+		cfg:  cfg,
+	}
 }
 
 type TimeToSlotFn func(timestamp uint64) (uint64, error)