initial statistics collection setup

eth/common/eth_types.nim

@@ -168,6 +168,9 @@ type
     OK
     Error
 
+  NimbusStats* = object
+    num_peers*: int
+
 when BlockNumber is int64:
   ## The goal of these templates is to make it easier to switch
   ## the block number type to a different representation

eth/common/utils.nim

@@ -8,3 +8,5 @@ proc parseAddress*(hexString: string): EthAddress =
 proc `$`*(a: EthAddress): string =
   a.toHex()
 
+var nimbusStats*: NimbusStats
+

eth/p2p/peer_pool.nim

@@ -3,7 +3,7 @@
 
 import
   os, tables, times, random, sequtils, options,
-  chronos, chronicles, eth/[rlp, keys],
+  chronos, chronicles, eth/[rlp, keys, common],
   private/p2p_types, discovery, kademlia, rlpx
 
 const
@@ -110,6 +110,7 @@ proc getRandomBootnode(p: PeerPool): Option[Node] =
 proc addPeer*(pool: PeerPool, peer: Peer) =
   doAssert(peer.remote notin pool.connectedNodes)
   pool.connectedNodes[peer.remote] = peer
+  inc(nimbusStats.num_peers)
   for o in pool.observers.values:
     if not o.onPeerConnected.isNil:
       if o.protocol.isNil or peer.supports(o.protocol):

eth/p2p/rlpx.nim

@@ -787,8 +787,9 @@ proc removePeer(network: EthereumNode, peer: Peer) =
   # have been dropped already from the peers side.
   # E.g. when receiving a p2p.disconnect message from a peer, a race will happen
   # between which side disconnects first.
-  if network.peerPool != nil and not peer.remote.isNil:
+  if network.peerPool != nil and not peer.remote.isNil and peer.remote in network.peerPool.connectedNodes:
     network.peerPool.connectedNodes.del(peer.remote)
+    dec(nimbusStats.num_peers)
 
     # Note: we need to do this check as disconnect (and thus removePeer)
     # currently can get called before the dispatcher is initialized.