adopt LC REST API with v0 suffix (without proofs)

Adopts the light client data REST API used by Lodestar as defined in
ethereum/beacon-APIs#181 with a v0 suffix.

Requests:
- `/eth/v0/beacon/light_client/bootstrap/{block_root}`
- `/eth/v0/beacon/light_client/updates?start_period={start_period}&count={count}`
- `/eth/v0/beacon/light_client/finality_update`
- `/eth/v0/beacon/light_client/optimistic_update`

HTTP Server-Sent Events (SSE):
- `light_client_finality_update_v0`
- `light_client_optimistic_update_v0`

More work is needed to adopt the proofs endpoint, it is not included.

beacon_chain/beacon_node.nim

@@ -21,7 +21,7 @@ import
   ./consensus_object_pools/[
     blockchain_dag, block_quarantine, exit_pool, attestation_pool,
     sync_committee_msg_pool],
-  ./spec/datatypes/base,
+  ./spec/datatypes/[base, altair],
   ./sync/[optimistic_sync_light_client, sync_manager, request_manager],
   ./validators/[action_tracker, validator_monitor, validator_pool],
   ./rpc/state_ttl_cache
@@ -41,6 +41,8 @@ type
     blocksQueue*: AsyncEventQueue[ForkedTrustedSignedBeaconBlock]
     headQueue*: AsyncEventQueue[HeadChangeInfoObject]
     reorgQueue*: AsyncEventQueue[ReorgInfoObject]
+    finUpdateQueue*: AsyncEventQueue[altair.LightClientFinalityUpdate]
+    optUpdateQueue*: AsyncEventQueue[altair.LightClientOptimisticUpdate]
     attestQueue*: AsyncEventQueue[Attestation]
     contribQueue*: AsyncEventQueue[SignedContributionAndProof]
     exitQueue*: AsyncEventQueue[SignedVoluntaryExit]

beacon_chain/nimbus_beacon_node.nim

@@ -161,9 +161,9 @@ proc loadChainDag(
   proc onChainReorg(data: ReorgInfoObject) =
     eventBus.reorgQueue.emit(data)
   proc onLightClientFinalityUpdate(data: altair.LightClientFinalityUpdate) =
-    discard
+    eventBus.finUpdateQueue.emit(data)
   proc onLightClientOptimisticUpdate(data: altair.LightClientOptimisticUpdate) =
-    discard
+    eventBus.optUpdateQueue.emit(data)
 
   let
     chainDagFlags =
@@ -1315,6 +1315,8 @@ proc installRestHandlers(restServer: RestServerRef, node: BeaconNode) =
   restServer.router.installNimbusApiHandlers(node)
   restServer.router.installNodeApiHandlers(node)
   restServer.router.installValidatorApiHandlers(node)
+  if node.config.lightClientDataServe:
+    restServer.router.installLightClientApiHandlers(node)
 
 proc installMessageValidators(node: BeaconNode) =
   # https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/p2p-interface.md#attestations-and-aggregation

beacon_chain/rpc/rest_api.nim

@@ -1,22 +1,28 @@
-# Copyright (c) 2018-2021 Status Research & Development GmbH
+# beacon_chain
+# Copyright (c) 2018-2022 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * 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.
 
+{.push raises: [Defect].}
+
 ## The `rest_api` module is a server implementation for the common REST API for
 ## Ethereum 2 found at https://ethereum.github.io/eth2.0-APIs/#
 ## along with several nimbus-specific extensions. It is used by the validator
 ## client as well as many community utilities.
 ## A corresponding client can be found in the
 ## `spec/eth2_apis/rest_beacon_client` module
+
 import
   "."/[
     rest_utils,
     rest_beacon_api, rest_config_api, rest_debug_api, rest_event_api,
-    rest_nimbus_api, rest_node_api, rest_validator_api, rest_key_management_api]
+    rest_key_management_api, rest_light_client_api, rest_nimbus_api,
+    rest_node_api, rest_validator_api]
 
 export
   rest_utils,
   rest_beacon_api, rest_config_api, rest_debug_api, rest_event_api,
-  rest_nimbus_api, rest_node_api, rest_validator_api, rest_key_management_api
+  rest_key_management_api, rest_light_client_api, rest_nimbus_api,
+  rest_node_api, rest_validator_api

beacon_chain/rpc/rest_constants.nim

@@ -1,3 +1,12 @@
+# beacon_chain
+# Copyright (c) 2021-2022 Status Research & Development GmbH
+# Licensed and distributed under either of
+#   * 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.
+
+{.push raises: [Defect].}
+
 import
   ../spec/beacon_time
 
@@ -190,3 +199,19 @@ const
     "Invalid Authorization Header"
   PrunedStateError* =
     "Trying to access a pruned historical state"
+  InvalidBlockRootValueError* =
+    "Invalid block root value"
+  InvalidSyncPeriodError* =
+    "Invalid sync committee period requested"
+  InvalidCountError* =
+    "Invalid count requested"
+  MissingStartPeriodValueError* =
+    "Missing `start_period` value"
+  MissingCountValueError* =
+    "Missing `count` value"
+  LCBootstrapUnavailable* =
+    "LC bootstrap unavailable"
+  LCFinUpdateUnavailable* =
+    "LC finality update unavailable"
+  LCOptUpdateUnavailable* =
+    "LC optimistic update unavailable"

beacon_chain/rpc/rest_event_api.nim

@@ -1,9 +1,12 @@
-# Copyright (c) 2018-2020 Status Research & Development GmbH
+# beacon_chain
+# Copyright (c) 2018-2022 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * 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.
 
+{.push raises: [Defect].}
+
 import
   stew/results,
   chronicles,
@@ -14,40 +17,20 @@ export rest_utils
 
 logScope: topics = "rest_eventapi"
 
-proc validateEventTopics(events: seq[EventTopic]): Result[EventTopics,
-                                                          cstring] =
+proc validateEventTopics(events: seq[EventTopic],
+                         withLightClient: bool): Result[EventTopics, cstring] =
   const NonUniqueError = cstring("Event topics must be unique")
+  const UnsupportedError = cstring("Unsupported event topic value")
   var res: set[EventTopic]
   for item in events:
-    case item
-    of EventTopic.Head:
-      if EventTopic.Head in res:
-        return err(NonUniqueError)
-      res.incl(EventTopic.Head)
-    of EventTopic.Block:
-      if EventTopic.Block in res:
-        return err(NonUniqueError)
-      res.incl(EventTopic.Block)
-    of EventTopic.Attestation:
-      if EventTopic.Attestation in res:
-        return err(NonUniqueError)
-      res.incl(EventTopic.Attestation)
-    of EventTopic.VoluntaryExit:
-      if EventTopic.VoluntaryExit in res:
-        return err(NonUniqueError)
-      res.incl(EventTopic.VoluntaryExit)
-    of EventTopic.FinalizedCheckpoint:
-      if EventTopic.FinalizedCheckpoint in res:
-        return err(NonUniqueError)
-      res.incl(EventTopic.FinalizedCheckpoint)
-    of EventTopic.ChainReorg:
-      if EventTopic.ChainReorg in res:
-        return err(NonUniqueError)
-      res.incl(EventTopic.ChainReorg)
-    of EventTopic.ContributionAndProof:
-      if EventTopic.ContributionAndProof in res:
-        return err(NonUniqueError)
-      res.incl(EventTopic.ContributionAndProof)
+    if item in res:
+      return err(NonUniqueError)
+    if not withLightClient and item in [
+        EventTopic.LightClientFinalityUpdate,
+        EventTopic.LightClientOptimisticUpdate]:
+      return err(UnsupportedError)
+    res.incl(item)
+
   if res == {}:
     err("Empty topics list")
   else:
@@ -105,14 +88,16 @@ proc eventHandler*[T](response: HttpResponseRef,
 
 proc installEventApiHandlers*(router: var RestRouter, node: BeaconNode) =
   # https://ethereum.github.io/beacon-APIs/#/Events/eventstream
+  # https://github.com/ethereum/beacon-APIs/pull/181
   router.api(MethodGet, "/eth/v1/events") do (
     topics: seq[EventTopic]) -> RestApiResponse:
     let eventTopics =
       block:
         if topics.isErr():
           return RestApiResponse.jsonError(Http400, "Invalid topics value",
                                            $topics.error())
-        let res = validateEventTopics(topics.get())
+        let res = validateEventTopics(topics.get(),
+                                      node.dag.lightClientDataServe)
         if res.isErr():
           return RestApiResponse.jsonError(Http400, "Invalid topics value",
                                            $res.error())
@@ -164,6 +149,16 @@ proc installEventApiHandlers*(router: var RestRouter, node: BeaconNode) =
           let handler = response.eventHandler(node.eventBus.contribQueue,
                                               "contribution_and_proof")
           res.add(handler)
+        if EventTopic.LightClientFinalityUpdate in eventTopics:
+          doAssert node.dag.lightClientDataServe
+          let handler = response.eventHandler(node.eventBus.finUpdateQueue,
+                                              "light_client_finality_update_v0")
+          res.add(handler)
+        if EventTopic.LightClientOptimisticUpdate in eventTopics:
+          doAssert node.dag.lightClientDataServe
+          let handler = response.eventHandler(node.eventBus.optUpdateQueue,
+                                              "light_client_optimistic_update_v0")
+          res.add(handler)
         res
 
     discard await one(handlers)

beacon_chain/rpc/rest_light_client_api.nim

@@ -0,0 +1,94 @@
+# beacon_chain
+# Copyright (c) 2021-2022 Status Research & Development GmbH
+# Licensed and distributed under either of
+#   * 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.
+
+{.push raises: [Defect].}
+
+import chronicles
+import ../beacon_node,
+       ./rest_utils
+
+logScope: topics = "rest_light_client"
+
+proc installLightClientApiHandlers*(router: var RestRouter, node: BeaconNode) =
+  # https://github.com/ethereum/beacon-APIs/pull/181
+  router.api(MethodGet,
+             "/eth/v0/beacon/light_client/bootstrap/{block_root}") do (
+    block_root: Eth2Digest) -> RestApiResponse:
+    doAssert node.dag.lightClientDataServe
+    let vroot = block:
+      if block_root.isErr():
+        return RestApiResponse.jsonError(Http400, InvalidBlockRootValueError,
+                                         $block_root.error())
+      block_root.get()
+
+    let bootstrap = node.dag.getLightClientBootstrap(vroot)
+    if bootstrap.isOk:
+      return RestApiResponse.jsonResponse(bootstrap)
+    else:
+      return RestApiResponse.jsonError(Http404, LCBootstrapUnavailable)
+
+  # https://github.com/ethereum/beacon-APIs/pull/181
+  router.api(MethodGet,
+             "/eth/v0/beacon/light_client/updates") do (
+    start_period: Option[SyncCommitteePeriod], count: Option[uint64]
+    ) -> RestApiResponse:
+    doAssert node.dag.lightClientDataServe
+    let vstart = block:
+      if start_period.isNone():
+        return RestApiResponse.jsonError(Http400, MissingStartPeriodValueError)
+      let rstart = start_period.get()
+      if rstart.isErr():
+        return RestApiResponse.jsonError(Http400, InvalidSyncPeriodError,
+                                         $rstart.error())
+      rstart.get()
+    let vcount = block:
+      if count.isNone():
+        return RestApiResponse.jsonError(Http400, MissingCountValueError)
+      let rcount = count.get()
+      if rcount.isErr():
+        return RestApiResponse.jsonError(Http400, InvalidCountError,
+                                         $rcount.error())
+      rcount.get()
+    let
+      headPeriod = node.dag.head.slot.sync_committee_period
+       # Limit number of updates in response
+      maxSupportedCount =
+        if vstart > headPeriod:
+          0'u64
+        else:
+          min(headPeriod + 1 - vstart, MAX_REQUEST_LIGHT_CLIENT_UPDATES)
+      numPeriods = min(vcount, maxSupportedCount)
+      onePastPeriod = vstart + numPeriods
+
+    var updates = newSeqOfCap[LightClientUpdate](numPeriods)
+    for period in startPeriod..<onePastPeriod:
+      let update = node.dag.getLightClientUpdateForPeriod(period)
+      if update.isSome:
+        updates.add update.get
+    return RestApiResponse.jsonResponse(updates)
+
+  # https://github.com/ethereum/beacon-APIs/pull/181
+  router.api(MethodGet,
+             "/eth/v0/beacon/light_client/finality_update") do (
+    ) -> RestApiResponse:
+    doAssert node.dag.lightClientDataServe
+    let finality_update = node.dag.getLightClientFinalityUpdate()
+    if finality_update.isSome:
+      return RestApiResponse.jsonResponse(finality_update)
+    else:
+      return RestApiResponse.jsonError(Http404, LCFinUpdateUnavailable)
+
+  # https://github.com/ethereum/beacon-APIs/pull/181
+  router.api(MethodGet,
+             "/eth/v0/beacon/light_client/optimistic_update") do (
+    ) -> RestApiResponse:
+    doAssert node.dag.lightClientDataServe
+    let optimistic_update = node.dag.getLightClientOptimisticUpdate()
+    if optimistic_update.isSome:
+      return RestApiResponse.jsonResponse(optimistic_update)
+    else:
+      return RestApiResponse.jsonError(Http404, LCOptUpdateUnavailable)

beacon_chain/rpc/rest_utils.nim

@@ -1,3 +1,12 @@
+# beacon_chain
+# Copyright (c) 2022 Status Research & Development GmbH
+# Licensed and distributed under either of
+#   * 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.
+
+{.push raises: [Defect].}
+
 import std/[options, macros],
        stew/byteutils, presto,
        ../spec/[forks],
@@ -37,6 +46,8 @@ proc validate(key: string, value: string): int =
     0
   of "{validator_id}":
     0
+  of "{block_root}":
+    0
   else:
     1
 

beacon_chain/spec/eth2_apis/eth2_rest_serialization.nim

@@ -1,3 +1,4 @@
+# beacon_chain
 # Copyright (c) 2018-2022 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
@@ -2186,6 +2187,11 @@ proc decodeString*(t: typedesc[Epoch], value: string): Result[Epoch, cstring] =
   let res = ? Base10.decode(uint64, value)
   ok(Epoch(res))
 
+proc decodeString*(t: typedesc[SyncCommitteePeriod],
+                   value: string): Result[SyncCommitteePeriod, cstring] =
+  let res = ? Base10.decode(uint64, value)
+  ok(SyncCommitteePeriod(res))
+
 proc decodeString*(t: typedesc[uint64],
                    value: string): Result[uint64, cstring] =
   Base10.decode(uint64, value)

beacon_chain/spec/eth2_apis/rest_types.nim

@@ -33,7 +33,7 @@ const
 type
   EventTopic* {.pure.} = enum
     Head, Block, Attestation, VoluntaryExit, FinalizedCheckpoint, ChainReorg,
-    ContributionAndProof
+    ContributionAndProof, LightClientFinalityUpdate, LightClientOptimisticUpdate
 
   EventTopics* = set[EventTopic]