Integrate litep2p into Polkadot SDK (#2944)

[litep2p](https://github.com/altonen/litep2p) is a libp2p-compatible P2P
networking library. It supports all of the features of `rust-libp2p`
that are currently being utilized by Polkadot SDK.

Compared to `rust-libp2p`, `litep2p` has a quite different architecture
which is why the new `litep2p` network backend is only able to use a
little of the existing code in `sc-network`. The design has been mainly
influenced by how we'd wish to structure our networking-related code in
Polkadot SDK: independent higher-levels protocols directly communicating
with the network over links that support bidirectional backpressure. A
good example would be `NotificationHandle`/`RequestResponseHandle`
abstractions which allow, e.g., `SyncingEngine` to directly communicate
with peers to announce/request blocks.

I've tried running `polkadot --network-backend litep2p` with a few
different peer configurations and there is a noticeable reduction in
networking CPU usage. For high load (`--out-peers 200`), networking CPU
usage goes down from ~110% to ~30% (80 pp) and for normal load
(`--out-peers 40`), the usage goes down from ~55% to ~18% (37 pp).

These should not be taken as final numbers because:

a) there are still some low-hanging optimization fruits, such as
enabling [receive window
auto-tuning](https://github.com/libp2p/rust-yamux/pull/176), integrating
`Peerset` more closely with `litep2p` or improving memory usage of the
WebSocket transport
b) fixing bugs/instabilities that incorrectly cause `litep2p` to do less
work will increase the networking CPU usage
c) verification in a more diverse set of tests/conditions is needed

Nevertheless, these numbers should give an early estimate for CPU usage
of the new networking backend.

This PR consists of three separate changes:
* introduce a generic `PeerId` (wrapper around `Multihash`) so that we
don't have use `NetworkService::PeerId` in every part of the code that
uses a `PeerId`
* introduce `NetworkBackend` trait, implement it for the libp2p network
stack and make Polkadot SDK generic over `NetworkBackend`
  * implement `NetworkBackend` for litep2p

The new library should be considered experimental which is why
`rust-libp2p` will remain as the default option for the time being. This
PR currently depends on the master branch of `litep2p` but I'll cut a
new release for the library once all review comments have been
addresses.

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Dmitry Markin <dmitry@markin.tech>
Co-authored-by: Alexandru Vasile <60601340+lexnv@users.noreply.github.com>
Co-authored-by: Alexandru Vasile <alexandru.vasile@parity.io>

templates/solochain/node/src/command.rs

@@ -183,7 +183,18 @@ pub fn run() -> sc_cli::Result<()> {
 		None => {
 			let runner = cli.create_runner(&cli.run)?;
 			runner.run_node_until_exit(|config| async move {
-				service::new_full(config).map_err(sc_cli::Error::Service)
+				match config.network.network_backend {
+					sc_network::config::NetworkBackendType::Libp2p => service::new_full::<
+						sc_network::NetworkWorker<
+							solochain_template_runtime::opaque::Block,
+							<solochain_template_runtime::opaque::Block as sp_runtime::traits::Block>::Hash,
+						>,
+					>(config)
+					.map_err(sc_cli::Error::Service),
+					sc_network::config::NetworkBackendType::Litep2p =>
+						service::new_full::<sc_network::Litep2pNetworkBackend>(config)
+							.map_err(sc_cli::Error::Service),
+				}
 			})
 		},
 	}

templates/solochain/node/src/service.rs

@@ -124,7 +124,11 @@ pub fn new_partial(config: &Configuration) -> Result<Service, ServiceError> {
 }
 
 /// Builds a new service for a full client.
-pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
+pub fn new_full<
+	N: sc_network::NetworkBackend<Block, <Block as sp_runtime::traits::Block>::Hash>,
+>(
+	config: Configuration,
+) -> Result<TaskManager, ServiceError> {
 	let sc_service::PartialComponents {
 		client,
 		backend,
@@ -136,14 +140,24 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 		other: (block_import, grandpa_link, mut telemetry),
 	} = new_partial(&config)?;
 
-	let mut net_config = sc_network::config::FullNetworkConfiguration::new(&config.network);
+	let mut net_config = sc_network::config::FullNetworkConfiguration::<
+		Block,
+		<Block as sp_runtime::traits::Block>::Hash,
+		N,
+	>::new(&config.network);
+	let metrics = N::register_notification_metrics(config.prometheus_registry());
 
+	let peer_store_handle = net_config.peer_store_handle();
 	let grandpa_protocol_name = sc_consensus_grandpa::protocol_standard_name(
 		&client.block_hash(0).ok().flatten().expect("Genesis block exists; qed"),
 		&config.chain_spec,
 	);
 	let (grandpa_protocol_config, grandpa_notification_service) =
-		sc_consensus_grandpa::grandpa_peers_set_config(grandpa_protocol_name.clone());
+		sc_consensus_grandpa::grandpa_peers_set_config::<_, N>(
+			grandpa_protocol_name.clone(),
+			metrics.clone(),
+			peer_store_handle,
+		);
 	net_config.add_notification_protocol(grandpa_protocol_config);
 
 	let warp_sync = Arc::new(sc_consensus_grandpa::warp_proof::NetworkProvider::new(
@@ -163,6 +177,7 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 			block_announce_validator_builder: None,
 			warp_sync_params: Some(WarpSyncParams::WithProvider(warp_sync)),
 			block_relay: None,
+			metrics,
 		})?;
 
 	if config.offchain_worker.enabled {
@@ -177,7 +192,7 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 				transaction_pool: Some(OffchainTransactionPoolFactory::new(
 					transaction_pool.clone(),
 				)),
-				network_provider: network.clone(),
+				network_provider: Arc::new(network.clone()),
 				enable_http_requests: true,
 				custom_extensions: |_| vec![],
 			})
@@ -205,7 +220,7 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 	};
 
 	let _rpc_handlers = sc_service::spawn_tasks(sc_service::SpawnTasksParams {
-		network: network.clone(),
+		network: Arc::new(network.clone()),
 		client: client.clone(),
 		keystore: keystore_container.keystore(),
 		task_manager: &mut task_manager,