Add feature flags for backwards compatibility (#521)

* Add feature flags for backwards compatibility

* improve readability of flags

* renaming flags

* remove fork schedule checks and flag

Author: avalonche

README.md

@@ -152,6 +152,7 @@ redis-cli DEL boost-relay/sepolia:validators-registration boost-relay/sepolia:va
 * `DISABLE_LOWPRIO_BUILDERS` - reject block submissions by low-prio builders
 * `FORCE_GET_HEADER_204` - force 204 as getHeader response
 * `ENABLE_IGNORABLE_VALIDATION_ERRORS` - enable ignorable validation errors
+* `USE_V2_PUBLISH_BLOCK_ENDPOINT` - uses the v2 publish block endpoint on the beacon node
 
 #### Development Environment Variables
 

beaconclient/prod_beacon_instance.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"os"
 	"time"
 
 	"github.com/attestantio/go-eth2-client/spec/capella"
@@ -16,14 +17,26 @@ import (
 type ProdBeaconInstance struct {
 	log       *logrus.Entry
 	beaconURI string
+
+	// feature flags
+	ffUseV2PublishBlockEndpoint bool
 }
 
 func NewProdBeaconInstance(log *logrus.Entry, beaconURI string) *ProdBeaconInstance {
 	_log := log.WithFields(logrus.Fields{
 		"component": "beaconInstance",
 		"beaconURI": beaconURI,
 	})
-	return &ProdBeaconInstance{_log, beaconURI}
+
+	client := &ProdBeaconInstance{_log, beaconURI, false}
+
+	// feature flags
+	if os.Getenv("USE_V2_PUBLISH_BLOCK_ENDPOINT") != "" {
+		_log.Warn("env: USE_V2_PUBLISH_BLOCK_ENDPOINT: use the v2 publish block endpoint")
+		client.ffUseV2PublishBlockEndpoint = true
+	}
+
+	return client
 }
 
 // HeadEventData represents the data of a head event
@@ -257,9 +270,14 @@ func (c *ProdBeaconInstance) GetURI() string {
 }
 
 func (c *ProdBeaconInstance) PublishBlock(block *common.SignedBeaconBlock, broadcastMode BroadcastMode) (code int, err error) {
-	uri := fmt.Sprintf("%s/eth/v2/beacon/blocks?broadcast_validation=%s", c.beaconURI, broadcastMode.String())
+	var uri string
+	if c.ffUseV2PublishBlockEndpoint {
+		uri = fmt.Sprintf("%s/eth/v2/beacon/blocks?broadcast_validation=%s", c.beaconURI, broadcastMode.String())
+	} else {
+		uri = fmt.Sprintf("%s/eth/v1/beacon/blocks", c.beaconURI)
+	}
 	headers := http.Header{}
-	headers.Add("Eth-Consensus-Version", common.ForkVersionStringCapella)
+	headers.Add("Eth-Consensus-Version", common.ForkVersionStringCapella) // optional in v1, required in v2
 	return fetchBeacon(http.MethodPost, uri, block, nil, nil, headers)
 }
 

services/api/service.go

@@ -53,8 +53,6 @@ var (
 	ErrRelayPubkeyMismatch        = errors.New("relay pubkey does not match existing one")
 	ErrServerAlreadyStarted       = errors.New("server was already started")
 	ErrBuilderAPIWithoutSecretKey = errors.New("cannot start builder API without secret key")
-	ErrMismatchedForkVersions     = errors.New("can not find matching fork versions as retrieved from beacon node")
-	ErrMissingForkVersions        = errors.New("invalid fork version from beacon node")
 )
 
 var (
@@ -408,6 +406,7 @@ func (api *RelayAPI) StartServer() (err error) {
 	if err != nil {
 		return err
 	}
+
 	var foundCapellaEpoch, foundDenebEpoch bool
 	for _, fork := range forkSchedule.Data {
 		log.Infof("forkSchedule: version=%s / epoch=%d", fork.CurrentVersion, fork.Epoch)
@@ -421,14 +420,10 @@ func (api *RelayAPI) StartServer() (err error) {
 		}
 	}
 
-	if !foundCapellaEpoch || !foundDenebEpoch {
-		return ErrMissingForkVersions
-	}
-
 	// Print fork version information
-	if hasReachedFork(currentSlot, api.denebEpoch) {
+	if foundDenebEpoch && hasReachedFork(currentSlot, api.denebEpoch) {
 		log.Infof("deneb fork detected (currentEpoch: %d / denebEpoch: %d)", common.SlotToEpoch(currentSlot), api.denebEpoch)
-	} else if hasReachedFork(currentSlot, api.capellaEpoch) {
+	} else if foundCapellaEpoch && hasReachedFork(currentSlot, api.capellaEpoch) {
 		log.Infof("capella fork detected (currentEpoch: %d / capellaEpoch: %d)", common.SlotToEpoch(currentSlot), api.capellaEpoch)
 	}