*: Gate authority discovery module behind feature flag

cli/src/lib.rs

@@ -87,13 +87,21 @@ struct ValidationWorkerCommand {
 	pub mem_id: String,
 }
 
+#[derive(Debug, StructOpt, Clone)]
+pub struct PolkadotSubParams {
+	#[structopt(long = "enable-authority-discovery")]
+	pub authority_discovery_enabled: bool,
+}
+
+cli::impl_augment_clap!(PolkadotSubParams);
+
 /// Parses polkadot specific CLI arguments and run the service.
 pub fn run<W>(worker: W, version: cli::VersionInfo) -> error::Result<()> where
 	W: Worker,
 {
-	match cli::parse_and_prepare::<PolkadotSubCommands, NoCustom, _>(&version, "parity-polkadot", std::env::args()) {
+	match cli::parse_and_prepare::<PolkadotSubCommands, PolkadotSubParams, _>(&version, "parity-polkadot", std::env::args()) {
 		cli::ParseAndPrepare::Run(cmd) => cmd.run(load_spec, worker,
-		|worker, _cli_args, _custom_args, mut config| {
+		|worker, cli_args, custom_args, mut config| {
 			info!("{}", version.name);
 			info!("  version {}", config.full_version());
 			info!("  by {}, 2017-2019", version.author);
@@ -108,6 +116,7 @@ pub fn run<W>(worker: W, version: cli::VersionInfo) -> error::Result<()> where
 			info!("Node name: {}", config.name);
 			info!("Roles: {}", display_role(&config));
 			config.custom = worker.configuration();
+			config.custom.authority_discovery_enabled = custom_args.authority_discovery_enabled;
 			let runtime = Runtime::new().map_err(|e| format!("{:?}", e))?;
 			match config.roles {
 				service::Roles::LIGHT =>

service/src/lib.rs

@@ -54,13 +54,17 @@ pub struct CustomConfiguration {
 
 	/// Maximal `block_data` size.
 	pub max_block_data_size: Option<u64>,
+
+	/// Whether to enable or disable the authority discovery module.
+	pub authority_discovery_enabled: bool,
 }
 
 impl Default for CustomConfiguration {
 	fn default() -> Self {
 		Self {
 			collating_for: None,
 			max_block_data_size: None,
+			authority_discovery_enabled: false,
 		}
 	}
 }
@@ -164,6 +168,7 @@ pub fn new_full(config: Configuration<CustomConfiguration, GenesisConfig>)
 	};
 	let disable_grandpa = config.disable_grandpa;
 	let name = config.name.clone();
+	let authority_discovery_enabled = config.custom.authority_discovery_enabled;
 
 	// sentry nodes announce themselves as authorities to the network
 	// and should run the same protocols authorities do, but it should
@@ -283,18 +288,20 @@ pub fn new_full(config: Configuration<CustomConfiguration, GenesisConfig>)
 		let babe = babe::start_babe(babe_config)?;
 		service.spawn_essential_task(babe);
 
-		let future03_dht_event_rx = dht_event_rx.compat()
-			.map(|x| x.expect("<mpsc::channel::Receiver as Stream> never returns an error; qed"))
-			.boxed();
-		let authority_discovery = authority_discovery::AuthorityDiscovery::new(
-			service.client(),
-			service.network(),
-			service.keystore(),
-			future03_dht_event_rx,
-		);
-		let future01_authority_discovery = authority_discovery.map(|x| Ok(x)).compat();
+		if authority_discovery_enabled {
+			let future03_dht_event_rx = dht_event_rx.compat()
+				.map(|x| x.expect("<mpsc::channel::Receiver as Stream> never returns an error; qed"))
+				.boxed();
+			let authority_discovery = authority_discovery::AuthorityDiscovery::new(
+				service.client(),
+				service.network(),
+				service.keystore(),
+				future03_dht_event_rx,
+			);
+			let future01_authority_discovery = authority_discovery.map(|x| Ok(x)).compat();
 
-		service.spawn_task(future01_authority_discovery);
+			service.spawn_task(future01_authority_discovery);
+		}
 	}
 
 	// if the node isn't actively participating in consensus then it doesn't