From 9f37ffdc621bc25be0ee8bc0d503f6aed8b927a7 Mon Sep 17 00:00:00 2001
From: Etan Kissling <etan@status.im>
Date: Wed, 27 Mar 2024 16:00:02 +0100
Subject: [PATCH] suspend light client sync while branch discovery is in
 progress

---
 beacon_chain/beacon_node_light_client.nim  |  6 ++++
 beacon_chain/light_client.nim              | 12 ++++++--
 beacon_chain/nimbus_beacon_node.nim        |  6 ++++
 beacon_chain/sync/light_client_manager.nim | 33 ++++++++++++----------
 4 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/beacon_chain/beacon_node_light_client.nim b/beacon_chain/beacon_node_light_client.nim
index 3f0af21e2..9a63649ab 100644
--- a/beacon_chain/beacon_node_light_client.nim
+++ b/beacon_chain/beacon_node_light_client.nim
@@ -125,6 +125,12 @@ proc startLightClient*(node: BeaconNode) =
 
   node.lightClient.start()
 
+proc stopLightClient*(node: BeaconNode) {.async: (raises: []).} =
+  if not node.config.syncLightClient:
+    return
+
+  await node.lightClient.stop()
+
 proc installLightClientMessageValidators*(node: BeaconNode) =
   let eth2Processor =
     if node.config.lightClientDataServe:
diff --git a/beacon_chain/light_client.nim b/beacon_chain/light_client.nim
index e757be813..977947cbc 100644
--- a/beacon_chain/light_client.nim
+++ b/beacon_chain/light_client.nim
@@ -43,7 +43,7 @@ type
     getBeaconTime: GetBeaconTimeFn
     store: ref ForkedLightClientStore
     processor: ref LightClientProcessor
-    manager: LightClientManager
+    manager: ref LightClientManager
     gossipState: GossipState
     onFinalizedHeader*, onOptimisticHeader*: LightClientHeaderCallback
     bootstrapObserver*: LightClientBootstrapObserver
@@ -173,7 +173,7 @@ proc createLightClient(
       else:
         GENESIS_SLOT.sync_committee_period
 
-  lightClient.manager = LightClientManager.init(
+  lightClient.manager = LightClientManager.new(
     lightClient.network, rng, getTrustedBlockRoot,
     bootstrapVerifier, updateVerifier, finalityVerifier, optimisticVerifier,
     isLightClientStoreInitialized, isNextSyncCommitteeKnown,
@@ -215,10 +215,18 @@ proc createLightClient*(
     cfg, forkDigests, getBeaconTime, genesis_validators_root, finalizationMode)
 
 proc start*(lightClient: LightClient) =
+  if lightClient.manager.isRunning:
+    return
   notice "Starting light client",
     trusted_block_root = lightClient.trustedBlockRoot
   lightClient.manager.start()
 
+proc stop*(lightClient: LightClient) {.async: (raises: [], raw: true).} =
+  if not lightClient.manager.isRunning:
+    return
+  notice "Stopping light client"
+  lightClient.manager.stop()
+
 proc resetToFinalizedHeader*(
     lightClient: LightClient,
     header: ForkedLightClientHeader,
diff --git a/beacon_chain/nimbus_beacon_node.nim b/beacon_chain/nimbus_beacon_node.nim
index 96945882b..0471ddc73 100644
--- a/beacon_chain/nimbus_beacon_node.nim
+++ b/beacon_chain/nimbus_beacon_node.nim
@@ -1584,6 +1584,12 @@ proc onSlotEnd(node: BeaconNode, slot: Slot) {.async.} =
   if not node.syncManager.inProgress:
     await node.branchDiscovery.stop()
 
+  # Light client is stopped while branch discovery is ongoing
+  if node.branchDiscovery.state != BranchDiscoveryState.Stopped:
+    node.startLightClient()
+  else:
+    await node.stopLightClient()
+
 func formatNextConsensusFork(
     node: BeaconNode, withVanityArt = false): Opt[string] =
   let consensusFork =
diff --git a/beacon_chain/sync/light_client_manager.nim b/beacon_chain/sync/light_client_manager.nim
index 7abc451bf..0c18fc057 100644
--- a/beacon_chain/sync/light_client_manager.nim
+++ b/beacon_chain/sync/light_client_manager.nim
@@ -67,7 +67,7 @@ type
     getBeaconTime: GetBeaconTimeFn
     loopFuture: Future[void].Raising([CancelledError])
 
-func init*(
+func new*(
     T: type LightClientManager,
     network: Eth2Node,
     rng: ref HmacDrbgContext,
@@ -81,9 +81,9 @@ func init*(
     getFinalizedPeriod: GetSyncCommitteePeriodCallback,
     getOptimisticPeriod: GetSyncCommitteePeriodCallback,
     getBeaconTime: GetBeaconTimeFn
-): LightClientManager =
+): ref LightClientManager =
   ## Initialize light client manager.
-  LightClientManager(
+  (ref LightClientManager)(
     network: network,
     rng: rng,
     getTrustedBlockRoot: getTrustedBlockRoot,
@@ -99,16 +99,16 @@ func init*(
   )
 
 proc isGossipSupported*(
-    self: LightClientManager,
+    self: ref LightClientManager,
     period: SyncCommitteePeriod
 ): bool =
   ## Indicate whether the light client is sufficiently synced to accept gossip.
-  if not self.isLightClientStoreInitialized():
+  if not self[].isLightClientStoreInitialized():
     return false
 
   period.isGossipSupported(
-    finalizedPeriod = self.getFinalizedPeriod(),
-    isNextSyncCommitteeKnown = self.isNextSyncCommitteeKnown())
+    finalizedPeriod = self[].getFinalizedPeriod(),
+    isNextSyncCommitteeKnown = self[].isNextSyncCommitteeKnown())
 
 # https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.5/specs/altair/light-client/p2p-interface.md#getlightclientbootstrap
 proc doRequest(
@@ -381,13 +381,16 @@ proc loop(self: LightClientManager) {.async: (raises: [CancelledError]).} =
       isNextSyncCommitteeKnown = self.isNextSyncCommitteeKnown(),
       didLatestSyncTaskProgress = didProgress)
 
-proc start*(self: var LightClientManager) =
-  ## Start light client manager's loop.
-  doAssert self.loopFuture == nil
-  self.loopFuture = self.loop()
+func isRunning*(self: ref LightClientManager): bool =
+  self[].loopFuture != nil
 
-proc stop*(self: var LightClientManager) {.async: (raises: []).} =
+proc start*(self: ref LightClientManager) =
+  ## Start light client manager's loop.
+  doAssert self[].loopFuture == nil
+  self[].loopFuture = self[].loop()
+
+proc stop*(self: ref LightClientManager) {.async: (raises: []).} =
   ## Stop light client manager's loop.
-  if self.loopFuture != nil:
-    await noCancel self.loopFuture.cancelAndWait()
-    self.loopFuture = nil
+  if self[].loopFuture != nil:
+    await noCancel self[].loopFuture.cancelAndWait()
+    self[].loopFuture = nil