Double grandpa gossip duration for Kusama and test networks (#5448)

* Double grandpa gossip duration.

* Make resend period slightly larger.

So it won't get triggered by additional grandpa delay.

* Bump other values as well.

* Don't change gossip duration on Polkadot.

(and Westend as it is meant to be a testbed for Polkadot)

polkadot/node/service/src/lib.rs

@@ -1180,9 +1180,22 @@ where
 		}
 	}
 
+	// Reduce grandpa load on Kusama and test networks. This will slow down finality by
+	// approximately one slot duration, but will reduce load. We would like to see the impact on
+	// Kusama, see: https://github.com/paritytech/polkadot/issues/5464
+	let gossip_duration = if chain_spec.is_versi() ||
+		chain_spec.is_wococo() ||
+		chain_spec.is_rococo() ||
+		chain_spec.is_kusama()
+	{
+		Duration::from_millis(2000)
+	} else {
+		Duration::from_millis(1000)
+	};
+
 	let config = grandpa::Config {
 		// FIXME substrate#1578 make this available through chainspec
-		gossip_duration: Duration::from_millis(1000),
+		gossip_duration,
 		justification_period: 512,
 		name: Some(name),
 		observer_enabled: false,