NoMonitor and removed clock check for SyncManager. (#3420)

* Add `NoMonitor` flag to stop SyncManager from monitoring sync situation.

* Remove `toleranceValue` and `PeerScoreHeadTooNew`.

Co-authored-by: Etan Kissling <etan@status.im>

beacon_chain/networking/peer_scores.nim

@@ -17,8 +17,6 @@ const
   PeerScoreInvalidRequest* = -500
     ## This peer is sending malformed or nonsensical data
 
-  PeerScoreHeadTooNew* = -100
-    ## The peer reports a head newer than our wall clock slot
   PeerScoreNoStatus* = -100
     ## Peer did not answer `status` request.
   PeerScoreStaleStatus* = -50

beacon_chain/sync/sync_manager.nim

@@ -38,6 +38,9 @@ type
     Sleeping, WaitingPeer, UpdatingStatus, Requesting, Downloading, Queueing,
     Processing
 
+  SyncManagerFlag* {.pure.} = enum
+    NoMonitor
+
   SyncWorker*[A, B] = object
     future: Future[void]
     status: SyncWorkerStatus
@@ -46,7 +49,6 @@ type
     pool: PeerPool[A, B]
     responseTimeout: chronos.Duration
     maxHeadAge: uint64
-    toleranceValue: uint64
     getLocalHeadSlot: GetSlotCallback
     getLocalWallSlot: GetSlotCallback
     getSafeSlot: GetSlotCallback
@@ -66,6 +68,7 @@ type
     syncStatus*: string
     direction: SyncQueueKind
     ident*: string
+    flags: set[SyncManagerFlag]
 
   SyncMoment* = object
     stamp*: chronos.Moment
@@ -118,7 +121,7 @@ proc newSyncManager*[A, B](pool: PeerPool[A, B],
                            blockVerifier: BlockVerifier,
                            maxHeadAge = uint64(SLOTS_PER_EPOCH * 1),
                            chunkSize = uint64(SLOTS_PER_EPOCH),
-                           toleranceValue = uint64(1),
+                           flags: set[SyncManagerFlag] = {},
                            ident = "main"
                            ): SyncManager[A, B] =
   let (getFirstSlot, getLastSlot, getSafeSlot) = case direction
@@ -140,7 +143,8 @@ proc newSyncManager*[A, B](pool: PeerPool[A, B],
     blockVerifier: blockVerifier,
     notInSyncEvent: newAsyncEvent(),
     direction: direction,
-    ident: ident
+    ident: ident,
+    flags: flags
   )
   res.initQueue()
   res
@@ -256,17 +260,6 @@ proc syncStep[A, B](man: SyncManager[A, B], index: int, peer: A) {.async.} =
     headSlot = man.getLocalHeadSlot()
     wallSlot = man.getLocalWallSlot()
 
-    if peerSlot > wallSlot + man.toleranceValue:
-      # If the peer reports a head slot higher than our wall slot, something is
-      # wrong: our clock is off or the peer is on a different network (or
-      # dishonest)
-      peer.updateScore(PeerScoreHeadTooNew)
-
-      warn "Peer reports a head newer than our wall clock - clock out of sync?",
-            wall_clock_slot = wallSlot, remote_head_slot = peerSlot,
-            local_head_slot = headSlot, tolerance_value = man.toleranceValue
-      return
-
   if man.remainingSlots() <= man.maxHeadAge:
     logScope:
       peer = peer
@@ -491,6 +484,21 @@ proc toTimeLeftString*(d: Duration): string =
       res = res & "00m"
     res
 
+proc syncClose[A, B](man: SyncManager[A, B], guardTaskFut: Future[void],
+                     speedTaskFut: Future[void]) {.async.} =
+  guardTaskFut.cancel()
+  speedTaskFut.cancel()
+  await allFutures(guardTaskFut, speedTaskFut)
+  let pendingTasks =
+    block:
+      var res: seq[Future[void]]
+      for worker in man.workers:
+        doAssert(worker.status in {Sleeping, WaitingPeer})
+        worker.future.cancel()
+        res.add(worker.future)
+      res
+  await allFutures(pendingTasks)
+
 proc syncLoop[A, B](man: SyncManager[A, B]) {.async.} =
   logScope:
     sync_ident = man.ident
@@ -595,6 +603,15 @@ proc syncLoop[A, B](man: SyncManager[A, B]) {.async.} =
         case man.direction
         of SyncQueueKind.Forward:
           if man.inProgress:
+            if SyncManagerFlag.NoMonitor in man.flags:
+              await man.syncClose(guardTaskFut, averageSpeedTaskFut)
+              man.inProgress = false
+              debug "Forward synchronization process finished, exiting",
+                    wall_head_slot = wallSlot, local_head_slot = headSlot,
+                    difference = (wallSlot - headSlot),
+                    max_head_age = man.maxHeadAge
+              break
+            else:
               man.inProgress = false
               debug "Forward synchronization process finished, sleeping",
                     wall_head_slot = wallSlot, local_head_slot = headSlot,
@@ -611,19 +628,7 @@ proc syncLoop[A, B](man: SyncManager[A, B]) {.async.} =
           # workers, guard task and speed calculation task).
           # We first need to cancel and wait for guard task, because otherwise
           # it will be able to restore cancelled workers.
-          guardTaskFut.cancel()
-          averageSpeedTaskFut.cancel()
-          await allFutures(guardTaskFut, averageSpeedTaskFut)
-          let pendingTasks =
-            block:
-              var res: seq[Future[void]]
-              for worker in man.workers:
-                # Because `pending == 0` there should be no active workers.
-                doAssert(worker.status in {Sleeping, WaitingPeer})
-                worker.future.cancel()
-                res.add(worker.future)
-              res
-          await allFutures(pendingTasks)
+          await man.syncClose(guardTaskFut, averageSpeedTaskFut)
           man.inProgress = false
           debug "Backward synchronization process finished, exiting",
                 wall_head_slot = wallSlot, local_head_slot = headSlot,