Tuning getStatusPeriod() function to be more precise in edge-cases.

Author: cheatfate

beacon_chain/sync/sync_overseer2.nim

@@ -970,20 +970,31 @@ proc getStatusPeriod*(
     peerFinalizedCheckpoint = peer.getFinalizedCheckpoint()
     secondsPerSlot = int(dag.cfg.timeParams.SECONDS_PER_SLOT)
 
+  if peerFinalizedCheckpoint.epoch < overseer.lastSeenCheckpoint.get.epoch:
+    # Peer is not in sync with the network.
+    return chronos.seconds(10 * secondsPerSlot)
+
   if localHead.slot.epoch() < peerFinalizedCheckpoint.epoch:
     # We are behind peer's finalized checkpoint, performing forward syncing.
     # 10 slots (mainnet: 2.minutes)
-    chronos.seconds(10 * secondsPerSlot)
-  else:
-    if peerHead.slot.epoch() - peerFinalizedCheckpoint.epoch >= 3:
-      # In periods of non-finality we try to follow every peer's head, in
-      # this case we should update peer's status very often.
-      # 1 slot (mainnet: 12.seconds)
-      chronos.seconds(1 * secondsPerSlot)
-    else:
-      # Node is optimistically synced or almost synced.
-      # 5 slots (mainnet: 1.minutes)
-      chronos.seconds(5 * secondsPerSlot)
+    return chronos.seconds(10 * secondsPerSlot)
+
+  if (localHead.slot >= peerHead.slot) and
+     (localHead.slot < overseer.lastSeenHead.get.slot):
+    # Peer's head slot is behind ours, but we still not in sync with network.
+    # So we need to refresh status information immediately.
+    return chronos.seconds(0)
+
+  if peerHead.slot < overseer.lastSeenHead.get.slot:
+    # Peer's head is behind network's peer head.
+    return chronos.seconds(1 * secondsPerSlot)
+
+  if localHead.slot == overseer.lastSeenHead.get.slot:
+    # Node is optimistically synced
+    return chronos.seconds(5 * secondsPerSlot)
+
+  # Node is almost synced, but still behind peer's head.
+  chronos.seconds(1 * secondsPerSlot)
 
 func getMissingSidecarsRoots(entry: SyncDagEntryRef): seq[BlockId] =
   var res: seq[BlockId]