gossip: choose a random subset on send instead of limiting connections (#2776)

* gossip: choose random subset on send

* naming bikeshed

polkadot/node/network/protocol/src/lib.rs

@@ -40,6 +40,9 @@ pub mod request_response;
 
 /// A version of the protocol.
 pub type ProtocolVersion = u32;
+/// The minimum amount of peers to send gossip messages to.
+pub const MIN_GOSSIP_PEERS: usize = 25;
+
 
 /// An error indicating that this the over-arching message type had the wrong variant
 #[derive(Debug, Clone, Copy, PartialEq)]

polkadot/node/network/protocol/src/peer_set.rs

@@ -57,7 +57,8 @@ impl PeerSet {
 				notifications_protocol: protocol,
 				max_notification_size,
 				set_config: sc_network::config::SetConfig {
-					in_peers: 25,
+					// we want our gossip subset to always include reserved peers
+					in_peers: super::MIN_GOSSIP_PEERS as u32 / 2,
 					out_peers: 0,
 					reserved_nodes: Vec::new(),
 					non_reserved_mode: sc_network::config::NonReservedPeerMode::Accept,