Number of REST fixes. (#2987)

* Initial commit.

* Fix path.

* Add validator keys to indices cache mechanism.
Move syncComitteeParticipants to common place.

* Fix sync participants order issue.

* Fix error code when state could not be found.
Refactor `state/validators` to use keysToIndices mechanism.

* Fix RestValidatorIndex to ValidatorIndex conversion TODOs.

* Address review comments.

* Fix REST test rules.

beacon_chain/beacon_node_common.nim

@@ -70,6 +70,7 @@ type
     beaconClock*: BeaconClock
     taskpool*: TaskPoolPtr
     onAttestationSent*: OnAttestationCallback
+    restKeysCache*: Table[ValidatorPubKey, ValidatorIndex]
 
 const
   MaxEmptySlotCount* = uint64(10*60) div SECONDS_PER_SLOT

beacon_chain/consensus_object_pools/blockchain_dag.nim

@@ -1037,6 +1037,18 @@ iterator syncSubcommittee*(
     yield syncCommittee[i]
     inc i
 
+iterator syncSubcommitteePairs*(
+    syncCommittee: openarray[ValidatorIndex],
+    committeeIdx: SyncCommitteeIndex): tuple[validatorIdx: ValidatorIndex,
+                                             committeeIdx: int] =
+  var
+    i = committeeIdx.asInt * SYNC_SUBCOMMITTEE_SIZE
+    onePastEndIdx = min(syncCommittee.len, i + SYNC_SUBCOMMITTEE_SIZE)
+
+  while i < onePastEndIdx:
+    yield (syncCommittee[i], i)
+    inc i
+
 func syncCommitteeParticipants*(dagParam: ChainDAGRef,
                                 slotParam: Slot): seq[ValidatorPubKey] =
   # TODO:

beacon_chain/nimbus_beacon_node.nim

@@ -411,9 +411,13 @@ proc init*(T: type BeaconNode,
     requestManager: RequestManager.init(network, blockProcessor),
     beaconClock: beaconClock,
     taskpool: taskpool,
-    onAttestationSent: onAttestationSent
+    onAttestationSent: onAttestationSent,
   )
 
+  # initialize REST server cache tables.
+  if config.restEnabled:
+    node.restKeysCache = initTable[ValidatorPubKey, ValidatorIndex]()
+
   # set topic validation routine
   network.setValidTopics(
     block:

beacon_chain/rpc/rest_beacon_api.nim

@@ -99,24 +99,6 @@ proc toString*(kind: ValidatorFilterKind): string =
   of ValidatorFilterKind.WithdrawalDone:
     "withdrawal_done"
 
-func syncCommitteeParticipants*(forkedState: ForkedHashedBeaconState,
-  epoch: Epoch): Result[seq[ValidatorPubKey], cstring] =
-  withState(forkedState):
-    when stateFork >= forkAltair:
-      let
-        headSlot = state.data.slot
-        epochPeriod = syncCommitteePeriod(epoch.compute_start_slot_at_epoch())
-        currentPeriod = syncCommitteePeriod(headSlot)
-        nextPeriod = currentPeriod + 1'u64
-      if epochPeriod == currentPeriod:
-        ok(@(state.data.current_sync_committee.pubkeys.data))
-      elif epochPeriod == nextPeriod:
-        ok(@(state.data.next_sync_committee.pubkeys.data))
-      else:
-        err("Epoch is outside the sync committee period of the state")
-    else:
-      err("State's fork do not support sync committees")
-
 proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getGenesis
   router.api(MethodGet, "/api/eth/v1/beacon/genesis") do () -> RestApiResponse:
@@ -150,7 +132,7 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
         bres.get()
     node.withStateForBlockSlot(bslot):
       return RestApiResponse.jsonResponse((root: stateRoot))
-    return RestApiResponse.jsonError(Http500, InternalServerError)
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getStateFork
   router.api(MethodGet, "/api/eth/v1/beacon/states/{state_id}/fork") do (
@@ -182,7 +164,7 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
             getStateField(stateData.data, fork).epoch
         )
       )
-    return RestApiResponse.jsonError(Http500, InternalServerError)
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getStateFinalityCheckpoints
   router.api(MethodGet,
@@ -214,7 +196,7 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
           finalized: getStateField(stateData.data, finalized_checkpoint)
         )
       )
-    return RestApiResponse.jsonError(Http500, InternalServerError)
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getStateValidators
   router.api(MethodGet, "/api/eth/v1/beacon/states/{state_id}/validators") do (
@@ -259,18 +241,24 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
                                            $res.error())
         res.get()
 
-    let (keySet, indexSet) =
+    node.withStateForBlockSlot(bslot):
+      let
+        current_epoch = getStateField(stateData.data, slot).epoch()
+        validatorsCount = lenu64(getStateField(stateData.data, validators))
+
+      let indices =
         block:
-        var res1: HashSet[ValidatorPubKey]
-        var res2: HashSet[ValidatorIndex]
+          var keyset: HashSet[ValidatorPubKey]
+          var indexset: HashSet[ValidatorIndex]
           for item in validatorIds:
             case item.kind
             of ValidatorQueryKind.Key:
-            if item.key in res1:
-              return RestApiResponse.jsonError(Http400, UniqueValidatorKeyError)
-            res1.incl(item.key)
+              if item.key in keyset:
+                return RestApiResponse.jsonError(Http400,
+                                                 UniqueValidatorKeyError)
+              keyset.incl(item.key)
             of ValidatorQueryKind.Index:
-            let vitem =
+              let vindex =
                 block:
                   let vres = item.index.toValidatorIndex()
                   if vres.isErr():
@@ -281,37 +269,69 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
                     of ValidatorIndexError.UnsupportedValue:
                       return RestApiResponse.jsonError(Http500,
                                             UnsupportedValidatorIndexValueError)
-                vres.get()
-
-            if vitem in res2:
+                  let index = vres.get()
+                  if uint64(index) >= validatorsCount:
+                    return RestApiResponse.jsonError(Http400,
+                                                     ValidatorNotFoundError)
+                  if index in indexset:
                     return RestApiResponse.jsonError(Http400,
                                                      UniqueValidatorIndexError)
-            res2.incl(vitem)
-        (res1, res2)
+                  index
+              indexset.incl(vindex)
 
-    node.withStateForBlockSlot(bslot):
-      let current_epoch = get_current_epoch(node.dag.headState.data)
+          if len(keyset) > 0:
+            let optIndices = keysToIndices(node.restKeysCache, stateData.data,
+                                           keyset.toSeq())
+            for item in optIndices:
+              if item.isNone():
+                return RestApiResponse.jsonError(Http400,
+                                                 ValidatorNotFoundError)
+              let vindex = item.get()
+              if vindex in indexset:
+                return RestApiResponse.jsonError(Http400,
+                                                 UniqueValidatorIndexError)
+              indexset.incl(vindex)
+          indexset.toSeq()
+
+      let response =
+        block:
           var res: seq[RestValidator]
-      for index, validator in getStateField(stateData.data, validators).pairs():
-        let includeFlag =
-          (len(keySet) == 0) and (len(indexSet) == 0) or
-          (len(indexSet) > 0 and (ValidatorIndex(index) in indexSet)) or
-          (len(keySet) > 0 and (validator.pubkey in keySet))
+          if len(indices) == 0:
+            # There is no indices, so we going to filter all the validators.
+            for index, validator in getStateField(stateData.data,
+                                                  validators).pairs():
+              let
+                balance = getStateField(stateData.data, balances)[index]
+                status =
+                  block:
                     let sres = validator.getStatus(current_epoch)
-        if sres.isOk():
-          let vstatus = sres.get()
-          let statusFlag = vstatus in validatorsMask
-          if includeFlag and statusFlag:
-            res.add(RestValidator(
-              index: ValidatorIndex(index),
-              balance:
-                Base10.toString(getStateField(stateData.data, balances)[index]),
-              status: toString(vstatus),
-              validator: validator
-            ))
-      return RestApiResponse.jsonResponse(res)
-
-    return RestApiResponse.jsonError(Http500, InternalServerError)
+                    if sres.isErr():
+                      return RestApiResponse.jsonError(Http400,
+                                                   ValidatorStatusNotFoundError,
+                                                   $sres.get())
+                    sres.get()
+              if status in validatorsMask:
+                res.add(RestValidator.init(ValidatorIndex(index), balance,
+                                           toString(status), validator))
+          else:
+            for index in indices:
+              let
+                validator = getStateField(stateData.data, validators)[index]
+                balance = getStateField(stateData.data, balances)[index]
+                status =
+                  block:
+                    let sres = validator.getStatus(current_epoch)
+                    if sres.isErr():
+                      return RestApiResponse.jsonError(Http400,
+                                                   ValidatorStatusNotFoundError,
+                                                   $sres.get())
+                    sres.get()
+              if status in validatorsMask:
+                res.add(RestValidator.init(index, balance, toString(status),
+                                           validator))
+          res
+      return RestApiResponse.jsonResponse(response)
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getStateValidator
   router.api(MethodGet,
@@ -337,33 +357,21 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
       return RestApiResponse.jsonError(Http400, InvalidValidatorIdValueError,
                                        $validator_id.error())
     node.withStateForBlockSlot(bslot):
-      let current_epoch = get_current_epoch(node.dag.headState.data)
+      let
+        current_epoch = getStateField(stateData.data, slot).epoch()
+        validatorsCount = lenu64(getStateField(stateData.data, validators))
+
+      let vindex =
+        block:
           let vid = validator_id.get()
           case vid.kind
           of ValidatorQueryKind.Key:
-        for index, validator in getStateField(stateData.data,
-                                              validators).pairs():
-          if validator.pubkey == vid.key:
-            let sres = validator.getStatus(current_epoch)
-            if sres.isOk():
-              return RestApiResponse.jsonResponse(
-                (
-                  index: ValidatorIndex(index),
-                  balance:
-                    Base10.toString(
-                      getStateField(stateData.data, balances)[index]
-                    ),
-                  status: toString(sres.get()),
-                  validator: validator
-                )
-              )
-            else:
-              return RestApiResponse.jsonError(Http400,
-                                               ValidatorStatusNotFoundError)
-        return RestApiResponse.jsonError(Http404, ValidatorNotFoundError)
+            let optIndices = keysToIndices(node.restKeysCache, stateData.data,
+                                           [vid.key])
+            if optIndices[0].isNone():
+              return RestApiResponse.jsonError(Http400, ValidatorNotFoundError)
+            optIndices[0].get()
           of ValidatorQueryKind.Index:
-        let vindex =
-          block:
             let vres = vid.index.toValidatorIndex()
             if vres.isErr():
               case vres.error()
@@ -373,28 +381,26 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
               of ValidatorIndexError.UnsupportedValue:
                 return RestApiResponse.jsonError(Http500,
                                             UnsupportedValidatorIndexValueError)
-            vres.get()
+            let index = vres.get()
+            if uint64(index) >= validatorsCount:
+              return RestApiResponse.jsonError(Http400, ValidatorNotFoundError)
+            index
 
-        if uint64(vindex) >=
-          uint64(len(getStateField(stateData.data, validators))):
-          return RestApiResponse.jsonError(Http404, ValidatorNotFoundError)
-        let validator = getStateField(stateData.data, validators)[vindex]
+      let
+        validator = getStateField(stateData.data, validators)[vindex]
+        balance = getStateField(stateData.data, balances)[vindex]
+        status =
+          block:
             let sres = validator.getStatus(current_epoch)
-        if sres.isOk():
-          return RestApiResponse.jsonResponse(
-            (
-              index: vindex,
-              balance: Base10.toString(
-                         getStateField(stateData.data, balances)[vindex]
-                       ),
-              status: toString(sres.get()),
-              validator: validator
-            )
-          )
-        else:
+            if sres.isErr():
               return RestApiResponse.jsonError(Http400,
-                                           ValidatorStatusNotFoundError)
-    return RestApiResponse.jsonError(Http500, InternalServerError)
+                                               ValidatorStatusNotFoundError,
+                                               $sres.get())
+            toString(sres.get())
+      return RestApiResponse.jsonResponse(
+        RestValidator.init(vindex, balance, status, validator)
+      )
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getStateValidatorBalances
   router.api(MethodGet,
@@ -426,19 +432,25 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
           return RestApiResponse.jsonError(Http400,
                                            MaximumNumberOfValidatorIdsError)
         ires
-    let (keySet, indexSet) =
+
+    node.withStateForBlockSlot(bslot):
+      let
+        current_epoch = getStateField(stateData.data, slot).epoch()
+        validatorsCount = lenu64(getStateField(stateData.data, validators))
+
+      let indices =
         block:
-        var res1: HashSet[ValidatorPubKey]
-        var res2: HashSet[ValidatorIndex]
+          var keyset: HashSet[ValidatorPubKey]
+          var indexset: HashSet[ValidatorIndex]
           for item in validatorIds:
             case item.kind
             of ValidatorQueryKind.Key:
-            if item.key in res1:
+              if item.key in keyset:
                 return RestApiResponse.jsonError(Http400,
                                                  UniqueValidatorKeyError)
-            res1.incl(item.key)
+              keyset.incl(item.key)
             of ValidatorQueryKind.Index:
-            let vitem =
+              let vindex =
                 block:
                   let vres = item.index.toValidatorIndex()
                   if vres.isErr():
@@ -449,32 +461,48 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
                     of ValidatorIndexError.UnsupportedValue:
                       return RestApiResponse.jsonError(Http500,
                                             UnsupportedValidatorIndexValueError)
-                vres.get()
-            if vitem in res2:
+                  let index = vres.get()
+                  if uint64(index) >= validatorsCount:
+                    return RestApiResponse.jsonError(Http400,
+                                                     ValidatorNotFoundError)
+                  if index in indexset:
                     return RestApiResponse.jsonError(Http400,
                                                      UniqueValidatorIndexError)
-            res2.incl(vitem)
-        (res1, res2)
-    node.withStateForBlockSlot(bslot):
-      let current_epoch = get_current_epoch(node.dag.headState.data)
-      var res: seq[RestValidatorBalance]
-      for index, validator in getStateField(stateData.data, validators).pairs():
-        let includeFlag =
-          (len(keySet) == 0) and (len(indexSet) == 0) or
-          (len(indexSet) > 0 and (ValidatorIndex(index) in indexSet)) or
-          (len(keySet) > 0 and (validator.pubkey in keySet))
-        let sres = validator.getStatus(current_epoch)
-        if sres.isOk():
-          let vstatus = sres.get()
-          if includeFlag:
-            res.add(RestValidatorBalance(
-              index: ValidatorIndex(index),
-              balance:
-                Base10.toString(getStateField(stateData.data, balances)[index]),
-            ))
-      return RestApiResponse.jsonResponse(res)
+                  index
+              indexset.incl(vindex)
 
-    return RestApiResponse.jsonError(Http500, InternalServerError)
+          if len(keyset) > 0:
+            let optIndices = keysToIndices(node.restKeysCache, stateData.data,
+                                           keyset.toSeq())
+            for item in optIndices:
+              if item.isNone():
+                return RestApiResponse.jsonError(Http400,
+                                                 ValidatorNotFoundError)
+              let vindex = item.get()
+              if vindex in indexset:
+                return RestApiResponse.jsonError(Http400,
+                                                 UniqueValidatorIndexError)
+              indexset.incl(vindex)
+          indexset.toSeq()
+
+      let response =
+        block:
+          var res: seq[RestValidatorBalance]
+          if len(indices) == 0:
+            # There is no indices, so we going to filter all the validators.
+            for index, validator in getStateField(stateData.data,
+                                                  validators).pairs():
+              let balance = getStateField(stateData.data, balances)[index]
+              res.add(RestValidatorBalance.init(ValidatorIndex(index),
+                                                balance))
+          else:
+            for index in indices:
+              let balance = getStateField(stateData.data, balances)[index]
+              res.add(RestValidatorBalance.init(index, balance))
+          res
+      return RestApiResponse.jsonResponse(response)
+
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getEpochCommittees
   router.api(MethodGet,
@@ -564,7 +592,7 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
 
       return RestApiResponse.jsonResponse(res)
 
-    return RestApiResponse.jsonError(Http500, InternalServerError)
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getEpochSyncCommittees
   router.api(MethodGet,
@@ -618,16 +646,15 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
       let indices =
         block:
           var res: seq[ValidatorIndex]
-          let keyset = keys.toHashSet()
-          for index, validator in getStateField(stateData.data,
-                                                validators).pairs():
-            if validator.pubkey in keyset:
-              res.add(ValidatorIndex(uint64(index)))
-          res
-
-      if len(indices) != len(keys):
+          let optIndices = keysToIndices(node.restKeysCache, stateData().data,
+                                         keys)
+          for item in optIndices:
+            if item.isNone():
               return RestApiResponse.jsonError(Http500, InternalServerError,
                                               "Could not get validator indices")
+            res.add(item.get())
+          res
+
       let aggregates =
         block:
           var
@@ -645,7 +672,7 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
         validators: indices, validator_aggregates: aggregates)
       )
 
-    return RestApiResponse.jsonError(Http400, "Could not get requested state")
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
 
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getBlockHeaders
   router.api(MethodGet, "/api/eth/v1/beacon/headers") do (

beacon_chain/rpc/rest_utils.nim

@@ -1,4 +1,5 @@
-import presto,
+import std/options,
+       presto,
        nimcrypto/utils as ncrutils,
        ../spec/[forks],
        ../spec/eth2_apis/[rest_types, eth2_rest_serialization],
@@ -6,7 +7,7 @@ import presto,
        ../consensus_object_pools/[block_pools_types, blockchain_dag]
 
 export
-  eth2_rest_serialization, blockchain_dag, presto, rest_types
+  options, eth2_rest_serialization, blockchain_dag, presto, rest_types
 
 const
   MaxEpoch* = compute_epoch_at_slot(not(0'u64))
@@ -85,6 +86,8 @@ const
     "Invalid graffiti bytes value"
   InvalidEpochValueError* =
     "Invalid epoch value"
+  EpochFromFutureError* =
+    "Epoch value is far from the future"
   InvalidStateIdValueError* =
     "Invalid state identifier value"
   InvalidBlockIdValueError* =
@@ -114,7 +117,7 @@ const
   UniqueValidatorIndexError* =
     "Only unique validator's index are allowed"
   StateNotFoundError* =
-    "State not found"
+    "Could not get requested state"
   SlotNotFoundError* =
     "Slot number is too far away"
   SlotNotInNextWallSlotEpochError* =
@@ -322,5 +325,48 @@ proc toValidatorIndex*(value: RestValidatorIndex): Result[ValidatorIndex,
   else:
     doAssert(false, "ValidatorIndex type size is incorrect")
 
+func syncCommitteeParticipants*(forkedState: ForkedHashedBeaconState,
+  epoch: Epoch): Result[seq[ValidatorPubKey], cstring] =
+  withState(forkedState):
+    when stateFork >= forkAltair:
+      let
+        headSlot = state.data.slot
+        epochPeriod = syncCommitteePeriod(epoch.compute_start_slot_at_epoch())
+        currentPeriod = syncCommitteePeriod(headSlot)
+        nextPeriod = currentPeriod + 1'u64
+      if epochPeriod == currentPeriod:
+        ok(@(state.data.current_sync_committee.pubkeys.data))
+      elif epochPeriod == nextPeriod:
+        ok(@(state.data.next_sync_committee.pubkeys.data))
+      else:
+        err("Epoch is outside the sync committee period of the state")
+    else:
+      err("State's fork do not support sync committees")
+
+func keysToIndices*(cacheTable: var Table[ValidatorPubKey, ValidatorIndex],
+                    forkedState: ForkedHashedBeaconState,
+                    keys: openArray[ValidatorPubKey]
+                   ): seq[Option[ValidatorIndex]] =
+  var indices = newSeq[Option[ValidatorIndex]](len(keys))
+  var keyset =
+    block:
+      var res: Table[ValidatorPubKey, int]
+      for inputIndex, pubkey in keys.pairs():
+        # Try to search in cache first.
+        cacheTable.withValue(pubkey, vindex):
+          indices[inputIndex] = some(vindex[])
+        do:
+          res[pubkey] = inputIndex
+      res
+  if len(keyset) > 0:
+    for validatorIndex, validator in getStateField(forkedState,
+                                                   validators).pairs():
+      keyset.withValue(validator.pubkey, listIndex):
+        # Store pair (pubkey, index) into cache table.
+        cacheTable[validator.pubkey] = ValidatorIndex(validatorIndex)
+        # Fill result sequence.
+        indices[listIndex[]] = some(ValidatorIndex(validatorIndex))
+  indices
+
 proc getRouter*(): RestRouter =
   RestRouter.init(validate)

beacon_chain/rpc/rest_validator_api.nim

@@ -3,7 +3,7 @@
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
-import std/[typetraits, strutils]
+import std/[typetraits, strutils, sequtils]
 import stew/[results, base10], chronicles, json_serialization,
        json_serialization/std/[options, net],
        nimcrypto/utils as ncrutils
@@ -142,6 +142,117 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
         res
     return RestApiResponse.jsonResponseWRoot(duties, droot)
 
+  router.api(MethodPost, "/api/eth/v1/validator/duties/sync/{epoch}") do (
+    epoch: Epoch, contentBody: Option[ContentBody]) -> RestApiResponse:
+    let indexList =
+      block:
+        if contentBody.isNone():
+          return RestApiResponse.jsonError(Http400, EmptyRequestBodyError)
+        let dres = decodeBody(seq[RestValidatorIndex], contentBody.get())
+        if dres.isErr():
+          return RestApiResponse.jsonError(Http400,
+                                           InvalidValidatorIndexValueError,
+                                           $dres.error())
+        var res: seq[ValidatorIndex]
+        let items = dres.get()
+        for item in items:
+          let vres = item.toValidatorIndex()
+          if vres.isErr():
+            case vres.error()
+            of ValidatorIndexError.TooHighValue:
+              return RestApiResponse.jsonError(Http400,
+                                               TooHighValidatorIndexValueError)
+            of ValidatorIndexError.UnsupportedValue:
+              return RestApiResponse.jsonError(Http500,
+                                            UnsupportedValidatorIndexValueError)
+          res.add(vres.get())
+        if len(res) == 0:
+          return RestApiResponse.jsonError(Http400,
+                                           EmptyValidatorIndexArrayError)
+        res
+    let qepoch =
+      block:
+        if epoch.isErr():
+          return RestApiResponse.jsonError(Http400, InvalidEpochValueError,
+                                           $epoch.error())
+        let res = epoch.get()
+        if res > MaxEpoch:
+          return RestApiResponse.jsonError(Http400, EpochOverflowValueError)
+
+        if res > node.dag.head.slot.epoch() + 1:
+          if not(node.isSynced(node.dag.head)):
+            return RestApiResponse.jsonError(Http503, BeaconNodeInSyncError)
+          else:
+            return RestApiResponse.jsonError(Http400, EpochFromFutureError)
+        res
+
+    let bslot = node.dag.head.atSlot(qepoch.compute_start_slot_at_epoch())
+
+    node.withStateForBlockSlot(bslot):
+      let validatorsCount = lenu64(getStateField(stateData.data, validators))
+      let participants =
+        block:
+          let res = syncCommitteeParticipants(stateData().data, qepoch)
+          if res.isErr():
+            return RestApiResponse.jsonError(Http400,
+                                             $res.error())
+          let kres = res.get()
+          if len(kres) == 0:
+            return RestApiResponse.jsonError(Http500, InternalServerError,
+                                 "List of sync committee participants is empty")
+          kres
+
+      # TODO: We doing this because `participants` are stored as array of
+      # validator keys, so we need to convert it to indices.
+      let participantIndices =
+        block:
+          var res: seq[ValidatorIndex]
+          let optIndices = keysToIndices(node.restKeysCache, stateData().data,
+                                         participants)
+          for item in optIndices:
+            if item.isNone():
+              return RestApiResponse.jsonError(Http500, InternalServerError,
+                                              "Could not get validator indices")
+            res.add(item.get())
+          res
+
+      let validatorsSet =
+        block:
+          var res: Table[ValidatorIndex, int]
+          for listIndex, validatorIndex in indexList.pairs():
+            if uint64(validatorIndex) >= validatorsCount:
+              return RestApiResponse.jsonError(Http400,
+                                               ValidatorNotFoundError)
+            res[validatorIndex] = listIndex
+          res
+
+      template isEmpty(duty: RestSyncCommitteeDuty): bool =
+        len(duty.validator_sync_committee_indices) == 0
+
+      var duties =
+        block:
+          var res = newSeq[RestSyncCommitteeDuty](len(indexList))
+          for committeeIdx in allSyncCommittees():
+            for valIndex, arrIndex in syncSubcommitteePairs(participantIndices,
+                                                            committeeIdx):
+              let listIndex = validatorsSet.getOrDefault(valIndex, -1)
+              if listIndex >= 0:
+                if res[listIndex].isEmpty():
+                  let key =
+                    getStateField(stateData().data, validators)[valIndex].pubkey
+                  res[listIndex] = RestSyncCommitteeDuty(
+                    validator_index: valIndex,
+                    pubkey: key
+                  )
+                res[listIndex].validator_sync_committee_indices.add(
+                  committeeIdx)
+          res.keepItIf(not(isEmpty(it)))
+          res
+
+      return RestApiResponse.jsonResponse(duties)
+
+    return RestApiResponse.jsonError(Http404, StateNotFoundError)
+
   # https://ethereum.github.io/beacon-APIs/#/Validator/produceBlock
   router.api(MethodGet, "/api/eth/v1/validator/blocks/{slot}") do (
     slot: Slot, randao_reveal: Option[ValidatorSig],
@@ -558,6 +669,11 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
     "/eth/v1/validator/duties/proposer/{epoch}",
     "/api/eth/v1/validator/duties/proposer/{epoch}"
   )
+  router.redirect(
+    MethodPost,
+    "/eth/v1/validator/duties/sync/{epoch}",
+    "/api/eth/v1/validator/duties/sync/{epoch}"
+  )
   router.redirect(
     MethodGet,
     "/eth/v1/validator/blocks/{slot}",

beacon_chain/spec/eth2_apis/rest_types.nim

@@ -15,6 +15,7 @@
 
 import
   std/[json, typetraits],
+  stew/base10,
   ".."/forks,
   ".."/datatypes/[phase0, altair]
 
@@ -101,6 +102,11 @@ type
     validator_index*: ValidatorIndex
     slot*: Slot
 
+  RestSyncCommitteeDuty* = object
+    pubkey*: ValidatorPubKey
+    validator_index*: ValidatorIndex
+    validator_sync_committee_indices*: seq[SyncCommitteeIndex]
+
   RestCommitteeSubscription* = object
     validator_index*: ValidatorIndex
     committee_index*: CommitteeIndex
@@ -355,6 +361,9 @@ type
   ProduceBlockResponse* = DataEnclosedObject[phase0.BeaconBlock]
   ProduceBlockResponseV2* = ForkedBeaconBlock
 
+func `==`*(a, b: RestValidatorIndex): bool =
+  uint64(a) == uint64(b)
+
 func init*(t: typedesc[StateIdent], v: StateIdentType): StateIdent =
   StateIdent(kind: StateQueryKind.Named, value: v)
 
@@ -382,3 +391,13 @@ func init*(t: typedesc[ValidatorIdent], v: ValidatorPubKey): ValidatorIdent =
 func init*(t: typedesc[RestBlockInfo],
            v: ForkedTrustedSignedBeaconBlock): RestBlockInfo =
   RestBlockInfo(slot: v.slot(), blck: v.root())
+
+func init*(t: typedesc[RestValidator], index: ValidatorIndex,
+           balance: uint64, status: string,
+           validator: Validator): RestValidator =
+  RestValidator(index: index, balance: Base10.toString(balance),
+                status: status, validator: validator)
+
+func init*(t: typedesc[RestValidatorBalance], index: ValidatorIndex,
+           balance: uint64): RestValidatorBalance =
+  RestValidatorBalance(index: index, balance: Base10.toString(balance))

ncli/resttest-rules.json

@@ -544,7 +544,7 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "oneof", "value": ["404", "200"]},
+      "status": {"operator": "oneof", "value": ["400", "200"]},
     }
   },
   {
@@ -672,9 +672,9 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "200"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
-      "body": [{"operator": "jstructcmps", "start": ["data"], "value": [{"index": "", "balance": "", "status": "", "validator": {"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}}]}]
+      "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
   {
@@ -685,9 +685,9 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "200"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
-      "body": [{"operator": "jstructcmps", "start": ["data"], "value": [{"index": "", "balance": "", "status": "", "validator": {"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}}]}]
+      "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
   {
@@ -698,9 +698,9 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "200"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
-      "body": [{"operator": "jstructcmps", "start": ["data"], "value": [{"index": "", "balance": "", "status": "", "validator": {"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}}]}]
+      "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
   {
@@ -997,7 +997,7 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "oneof", "value": ["404", "200"]},
+      "status": {"operator": "oneof", "value": ["400", "200"]},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
     }
   },
@@ -1155,7 +1155,7 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "404"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
       "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
@@ -1168,7 +1168,7 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "404"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
       "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
@@ -1231,7 +1231,7 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "oneof", "value": ["404", "200"]},
+      "status": {"operator": "oneof", "value": ["400", "200"]},
     }
   },
   {
@@ -1359,9 +1359,9 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "200"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
-      "body": [{"operator": "jstructcmps", "start": ["data"], "value": [{"index": "", "balance": "", "status": "", "validator": {"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}}]}]
+      "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
   {
@@ -1372,9 +1372,9 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "200"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
-      "body": [{"operator": "jstructcmps", "start": ["data"], "value": [{"index": "", "balance": "", "status": "", "validator": {"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}}]}]
+      "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
   {
@@ -1385,9 +1385,9 @@
       "headers": {"Accept": "application/json"}
     },
     "response": {
-      "status": {"operator": "equals", "value": "200"},
+      "status": {"operator": "equals", "value": "400"},
       "headers": [{"key": "Content-Type", "value": "application/json", "operator": "equals"}],
-      "body": [{"operator": "jstructcmps", "start": ["data"], "value": [{"index": "", "balance": "", "status": "", "validator": {"pubkey": "", "withdrawal_credentials": "", "effective_balance": "", "slashed": false, "activation_eligibility_epoch": "", "activation_epoch": "", "exit_epoch": "", "withdrawable_epoch": ""}}]}]
+      "body": [{"operator": "jstructcmpns", "value": {"code": "", "message": ""}}]
     }
   },
   {