Implement the /eth/v1/validator/prepare_beacon_proposer end-point (#3901)

beacon_chain/beacon_node.nim

@@ -22,6 +22,7 @@ import
     blockchain_dag, block_quarantine, consensus_manager, exit_pool,
     attestation_pool, sync_committee_msg_pool],
   ./spec/datatypes/[base, altair],
+  ./spec/eth2_apis/dynamic_fee_recipients,
   ./sync/[optimistic_sync_light_client, sync_manager, request_manager],
   ./validators/[
     action_tracker, message_router, validator_monitor, validator_pool],
@@ -34,7 +35,7 @@ export
   eth2_network, eth1_monitor, optimistic_sync_light_client,
   request_manager, sync_manager, eth2_processor, blockchain_dag,
   block_quarantine, base, exit_pool,  message_router, validator_monitor,
-  consensus_manager
+  consensus_manager, dynamic_fee_recipients
 
 type
   EventBus* = object
@@ -86,6 +87,7 @@ type
     stateTtlCache*: StateTtlCache
     nextExchangeTransitionConfTime*: Moment
     router*: ref MessageRouter
+    dynamicFeeRecipientsStore*: DynamicFeeRecipientsStore
 
 const
   MaxEmptySlotCount* = uint64(10*60) div SECONDS_PER_SLOT

beacon_chain/nimbus_beacon_node.nim

@@ -787,7 +787,8 @@ proc init*(T: type BeaconNode,
     beaconClock: beaconClock,
     validatorMonitor: validatorMonitor,
     stateTtlCache: stateTtlCache,
-    nextExchangeTransitionConfTime: nextExchangeTransitionConfTime)
+    nextExchangeTransitionConfTime: nextExchangeTransitionConfTime,
+    dynamicFeeRecipientsStore: DynamicFeeRecipientsStore.init())
 
   node.initLightClient(
     rng, cfg, dag.forkDigests, getBeaconTime, dag.genesis_validators_root)
@@ -1237,6 +1238,7 @@ proc onSlotEnd(node: BeaconNode, slot: Slot) {.async.} =
   node.syncCommitteeMsgPool[].pruneData(slot)
   if slot.is_epoch:
     node.trackNextSyncCommitteeTopics(slot)
+    node.dynamicFeeRecipientsStore.pruneOldMappings(slot.epoch)
 
   # Update upcoming actions - we do this every slot in case a reorg happens
   let head = node.dag.head

beacon_chain/rpc/rest_constants.nim

@@ -165,6 +165,8 @@ const
     "Unable to decode sync committee subscription request(s)"
   InvalidContributionAndProofMessageError* =
     "Unable to decode contribute and proof message(s)"
+  InvalidPrepareBeaconProposerError* =
+    "Unable to decode prepare beacon proposer request"
   SyncCommitteeMessageValidationError* =
     "Some errors happened while validating sync committee message(s)"
   SyncCommitteeMessageValidationSuccess* =

beacon_chain/rpc/rest_validator_api.nim

@@ -721,7 +721,7 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
                               contentBody.get())
         if dres.isErr():
           return RestApiResponse.jsonError(Http400,
-                                        InvalidContributionAndProofMessageError)
+                                           InvalidContributionAndProofMessageError)
         dres.get()
 
     let pending =
@@ -759,6 +759,29 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
         ContributionAndProofValidationSuccess
       )
 
+  # https://ethereum.github.io/beacon-APIs/#/ValidatorRequiredApi/prepareBeaconProposer
+  router.api(MethodPost,
+             "/eth/v1/validator/prepare_beacon_proposer") do (
+    contentBody: Option[ContentBody]) -> RestApiResponse:
+    let
+      proposerData =
+        block:
+          if contentBody.isNone():
+            return RestApiResponse.jsonError(Http400, EmptyRequestBodyError)
+          let dres = decodeBody(PrepareBeaconProposerBody, contentBody.get())
+          if dres.isErr():
+            return RestApiResponse.jsonError(Http400,
+                                             InvalidPrepareBeaconProposerError)
+          dres.get()
+      currentEpoch = node.beaconClock.now.slotOrZero.epoch
+
+    node.dynamicFeeRecipientsStore.addMapping(
+      proposerData.validator_index,
+      proposerData.fee_recipient,
+      currentEpoch)
+
+    return RestApiResponse.response("", Http200, "text/plain")
+
   # Legacy URLS - Nimbus <= 1.5.5 used to expose the REST API with an additional
   # `/api` path component
   router.redirect(
@@ -821,3 +844,8 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
     "/api/eth/v1/validator/contribution_and_proofs",
     "/eth/v1/validator/contribution_and_proofs"
   )
+  router.redirect(
+    MethodPost,
+    "/api/eth/v1/validator/prepare_beacon_proposer",
+    "/eth/v1/validator/prepare_beacon_proposer"
+  )

beacon_chain/spec/eth2_apis/dynamic_fee_recipients.nim

@@ -0,0 +1,54 @@
+import
+  std/tables,
+  stew/results,
+  web3/ethtypes,
+  ../datatypes/base
+
+type
+  Entry = object
+    recipient: Eth1Address
+    addedAt: Epoch
+
+  DynamicFeeRecipientsStore* = object
+    mappings: Table[ValidatorIndex, Entry]
+
+func init*(T: type DynamicFeeRecipientsStore): T =
+  T(mappings: initTable[ValidatorIndex, Entry]())
+
+func addMapping*(store: var DynamicFeeRecipientsStore,
+                 validator: ValidatorIndex,
+                 feeRecipient: Eth1Address,
+                 currentEpoch: Epoch) =
+  store.mappings[validator] = Entry(recipient: feeRecipient,
+                                    addedAt: currentEpoch)
+
+func getDynamicFeeRecipient*(store: var DynamicFeeRecipientsStore,
+                             validator: ValidatorIndex,
+                             currentEpoch: Epoch): Opt[Eth1Address] =
+  store.mappings.withValue(validator, entry) do:
+    # https://ethereum.github.io/beacon-APIs/#/ValidatorRequiredApi/prepareBeaconProposer
+    #
+    # The information supplied for each validator index will persist
+    # through the epoch in which the call is submitted and for a further
+    # two epochs after that, or until the beacon node restarts.
+    #
+    # It is expected that validator clients will send this information
+    # periodically, for example each epoch, to ensure beacon nodes have
+    # correct and timely fee recipient information.
+    return if (currentEpoch - entry.addedAt) > 2:
+      err()
+    else:
+      ok entry.recipient
+  do:
+    return err()
+
+func pruneOldMappings*(store: var DynamicFeeRecipientsStore,
+                       currentEpoch: Epoch) =
+  var toPrune: seq[ValidatorIndex]
+
+  for idx, entry in store.mappings:
+    if (currentEpoch - entry.addedAt) > 2:
+      toPrune.add idx
+
+  for idx in toPrune:
+    store.mappings.del idx

beacon_chain/spec/eth2_apis/eth2_rest_serialization.nim

@@ -88,6 +88,7 @@ type
     ImportDistributedKeystoresBody |
     ImportRemoteKeystoresBody |
     KeystoresAndSlashingProtection |
+    PrepareBeaconProposerBody |
     ProposerSlashing |
     SetFeeRecipientRequest |
     SignedBlindedBeaconBlock |
@@ -123,6 +124,7 @@ type
     KeymanagerGenericError |
     KeystoresAndSlashingProtection |
     ListFeeRecipientResponse |
+    PrepareBeaconProposerBody |
     ProduceBlockResponseV2 |
     RestDutyError |
     RestGenericError |

beacon_chain/spec/eth2_apis/rest_types.nim

@@ -239,6 +239,10 @@ type
     epoch*: Epoch
     active*: bool
 
+  PrepareBeaconProposerBody* = object
+    validator_index*: ValidatorIndex
+    fee_recipient*: Eth1Address
+
   RestPublishedSignedBeaconBlock* = distinct ForkedSignedBeaconBlock
 
   RestPublishedBeaconBlock* = distinct ForkedBeaconBlock

beacon_chain/spec/eth2_apis/rest_validator_calls.nim

@@ -86,3 +86,8 @@ proc publishContributionAndProofs*(body: seq[RestSignedContributionAndProof]): R
      rest, endpoint: "/eth/v1/validator/contribution_and_proofs",
      meth: MethodPost.}
   ## https://ethereum.github.io/beacon-APIs/#/Validator/publishContributionAndProofs
+
+proc prepareBeaconProposer*(body: PrepareBeaconProposerBody): RestPlainResponse {.
+     rest, endpoint: "/eth/v1/validator/prepare_beacon_proposer",
+     meth: MethodPost.}
+  ## https://ethereum.github.io/beacon-APIs/#/ValidatorRequiredApi/prepareBeaconProposer

beacon_chain/validators/validator_duties.nim

@@ -305,6 +305,7 @@ proc getBlockProposalEth1Data*(node: BeaconNode,
       state, finalizedEpochRef.eth1_data,
       finalizedEpochRef.eth1_deposit_index)
 
+# TODO: This copies the entire BeaconState on each call
 proc forkchoice_updated(state: bellatrix.BeaconState,
                         head_block_hash: Eth2Digest,
                         finalized_block_hash: Eth2Digest,
@@ -340,7 +341,10 @@ proc get_execution_payload(
       await execution_engine.getPayload(payload_id.get))
 
 proc getExecutionPayload(
-    node: BeaconNode, proposalState: auto, pubkey: ValidatorPubKey):
+    node: BeaconNode, proposalState: auto,
+    epoch: Epoch,
+    validator_index: ValidatorIndex,
+    pubkey: ValidatorPubKey):
     Future[ExecutionPayload] {.async.} =
   # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/bellatrix/validator.md#executionpayload
 
@@ -374,8 +378,11 @@ proc getExecutionPayload(
           terminalBlockHash
       latestFinalized =
         node.dag.loadExecutionBlockRoot(node.dag.finalizedHead.blck)
-      feeRecipient = node.config.getSuggestedFeeRecipient(pubkey).valueOr:
+      dynamicFeeRecipient = node.dynamicFeeRecipientsStore.getDynamicFeeRecipient(
-        node.config.defaultFeeRecipient
+        validator_index, epoch)
+      feeRecipient = dynamicFeeRecipient.valueOr:
+        node.config.getSuggestedFeeRecipient(pubkey).valueOr:
+          node.config.defaultFeeRecipient
       payload_id = (await forkchoice_updated(
         proposalState.bellatrixData.data, latestHead, latestFinalized,
         feeRecipient,
@@ -461,6 +468,7 @@ proc makeBeaconBlockForHeadAndSlot*(node: BeaconNode,
         let pubkey = node.dag.validatorKey(validator_index)
         (await getExecutionPayload(
           node, proposalState,
+          slot.epoch, validator_index,
           # TODO https://github.com/nim-lang/Nim/issues/19802
           if pubkey.isSome: pubkey.get.toPubKey else: default(ValidatorPubKey))),
       noRollback, # Temporary state - no need for rollback