tweak rate limiting

beacon_chain/sync/branch_discovery.nim

@@ -107,10 +107,18 @@ proc discoverBranch(
     debug "Peer's head block root is already known"
     return
 
+  # Many peers disconnect on rate limit, we have to avoid getting hit by it
   const
-    maxRequestsPerBurst = 20
+    maxRequestsPerBurst = 15
-    burstDuration = chronos.seconds(40)
+    burstDuration = chronos.seconds(30)
   let bucket = TokenBucket.new(maxRequestsPerBurst, burstDuration)
+  template consumeTokens(numTokens: int) =
+    try:
+      await bucket.consume(numTokens)
+    except CancelledError as exc:
+      raise exc
+    except CatchableError as exc:
+      raiseAssert "TokenBucket.consume should not fail: " & $exc.msg
 
   var parentSlot = peerHeadSlot + 1
   logScope: parentSlot
@@ -123,17 +131,12 @@ proc discoverBranch(
       return
 
     debug "Discovering new branch from peer"
-    try:
+    consumeTokens(1)
-      await bucket.consume(1)
-    except CancelledError as exc:
-      raise exc
-    except CatchableError as exc:
-      raiseAssert "TokenBucket.consume should not fail: " & $exc.msg
     let rsp = await peer.beaconBlocksByRoot_v2(BlockRootsList @[blockRoot])
     if rsp.isErr:
       # `eth2_network` already descored according to the specific error
       debug "Failed to receive block", err = rsp.error
-      await sleepAsync(RESP_TIMEOUT_DUR)
+      consumeTokens(5)
       continue
     template blocks: untyped = rsp.get
 
@@ -141,7 +144,7 @@ proc discoverBranch(
     if blocks.len == 0:
       peer.updateScore(PeerScoreNoValues)
       debug "Received no blocks", numBlocks = blocks.len
-      await sleepAsync(RESP_TIMEOUT_DUR)
+      consumeTokens(5)
       continue
     if blocks.len > 1:
       peer.updateScore(PeerScoreBadResponse)
@@ -172,17 +175,12 @@ proc discoverBranch(
           debug "Failed to discover new branch from peer"
           return
 
-        try:
+        consumeTokens(1)
-          await bucket.consume(1)
-        except CancelledError as exc:
-          raise exc
-        except CatchableError as exc:
-          raiseAssert "TokenBucket.consume should not fail: " & $exc.msg
         let r = await peer.blobSidecarsByRoot(BlobIdentifierList blobIds)
         if r.isErr:
           # `eth2_network` already descored according to the specific error
           debug "Failed to receive blobs", err = r.error
-          await sleepAsync(RESP_TIMEOUT_DUR)
+          consumeTokens(5)
           continue
         template blobSidecars: untyped = r.unsafeGet
 
@@ -190,7 +188,7 @@ proc discoverBranch(
           peer.updateScore(PeerScoreMissingValues)
           debug "Received not all blobs",
             numBlobs = blobSidecars.len, expectedNumBlobs = blobIds.len
-          await sleepAsync(RESP_TIMEOUT_DUR)
+          consumeTokens(5)
           continue
         if blobSidecars.len > blobIds.len:
           peer.updateScore(PeerScoreBadResponse)
@@ -243,7 +241,9 @@ proc loop(self: ref BranchDiscovery) {.async: (raises: []).} =
   try:
     while true:
       await self[].isActive.wait()
-      await sleepAsync(RESP_TIMEOUT_DUR)
+
+      const pollInterval = chronos.seconds(2)
+      await sleepAsync(pollInterval)
 
       let peer =
         if self[].peerQueue.len > 0: