add exception handlers to transaction exchange code

nimbus/sync/handlers.nim

@@ -67,6 +67,8 @@ proc addToKnownByPeer(ctx: EthWireRef, txHashes: openArray[Hash256], peer: Peer,
 proc sendNewTxHashes(ctx: EthWireRef,
                      txHashes: seq[Hash256],
                      peers: seq[Peer]): Future[void] {.async.} =
+  try:
+
     for peer in peers:
       # Add to known tx hashes and get hashes still to send to peer
       var hashesToSend: seq[Hash256]
@@ -76,16 +78,28 @@ proc sendNewTxHashes(ctx: EthWireRef,
       if hashesToSend.len > 0:
         await peer.newPooledTransactionHashes(hashesToSend)
 
+  except TransportError:
+    debug "Transport got closed during sendNewTxHashes"
+  except CatchableError as e:
+    debug "Exception in sendNewTxHashes", exc = e.name, err = e.msg
+
 proc sendTransactions(ctx: EthWireRef,
                       txHashes: seq[Hash256],
                       txs: seq[Transaction],
                       peers: seq[Peer]): Future[void] {.async.} =
+  try:
+
     for peer in peers:
       # This is used to avoid re-sending along pooledTxHashes
       # announcements/re-broadcasts
       ctx.addToKnownByPeer(txHashes, peer)
       await peer.transactions(txs)
 
+  except TransportError:
+    debug "Transport got closed during sendTransactions"
+  except CatchableError as e:
+    debug "Exception in sendTransactions", exc = e.name, err = e.msg
+
 proc inPool(ctx: EthWireRef, txHash: Hash256): bool =
   let res = ctx.txPool.getItem(txHash)
   res.isOk
@@ -292,6 +306,8 @@ proc fetchTransactions(ctx: EthWireRef, reqHashes: seq[Hash256], peer: Peer): Fu
   debug "fetchTx: requesting txs",
     number = reqHashes.len
 
+  try:
+
     let res = await peer.getPooledTransactions(reqHashes)
     if res.isNone:
       error "not able to get pooled transactions"
@@ -308,13 +324,20 @@ proc fetchTransactions(ctx: EthWireRef, reqHashes: seq[Hash256], peer: Peer): Fu
 
     ctx.txPool.jobAddTxs(txs.transactions)
 
+  except TransportError:
+    debug "Transport got closed during fetchTransactions"
+    return
+  except CatchableError as e:
+    debug "Exception in fetchTransactions", exc = e.name, err = e.msg
+    return
+
   var newTxHashes = newSeqOfCap[Hash256](reqHashes.len)
   for txHash in reqHashes:
     if ctx.inPoolAndOk(txHash):
       newTxHashes.add txHash
 
   let peers = ctx.getPeers(peer)
-  if peers.len == 0:
+  if peers.len == 0 or newTxHashes.len == 0:
     return
 
   await ctx.sendNewTxHashes(newTxHashes, peers)