grandpa: add voting rule to pause new votes for a period (#904)

* grandpa: add voting rule to pause new votes for a period

* grandpa: increase delay

* grandpa: parse custom pause delay from cli

* grandpa: log scheduled pause on startup

* grandpa: rename parameter to grandpa_pause

* grandpa: make pause voting rule generic on block

* grandpa: add test for pause voting rule

* grandpa: add hardcoded pause

* collator: fix test compilation

polkadot/cli/src/cli.rs

@@ -75,4 +75,13 @@ pub struct Cli {
 	#[allow(missing_docs)]
 	#[structopt(long = "enable-authority-discovery")]
 	pub authority_discovery_enabled: bool,
+
+	/// Setup a GRANDPA scheduled voting pause.
+	///
+	/// This parameter takes two values, namely a block number and a delay (in
+	/// blocks). After the given block number is finalized the GRANDPA voter
+	/// will temporarily stop voting for new blocks until the given delay has
+	/// elapsed (i.e. until a block at height `pause_block + delay` is imported).
+	#[structopt(long = "grandpa-pause", number_of_values(2))]
+	pub grandpa_pause: Vec<u32>,
 }

polkadot/cli/src/command.rs

@@ -31,6 +31,14 @@ pub fn run(version: VersionInfo) -> sc_cli::Result<()> {
 	config.impl_name = "parity-polkadot";
 	let force_kusama = opt.run.force_kusama;
 
+	let grandpa_pause = if opt.grandpa_pause.is_empty() {
+		None
+	} else {
+		// should be enforced by cli parsing
+		assert_eq!(opt.grandpa_pause.len(), 2);
+		Some((opt.grandpa_pause[0], opt.grandpa_pause[1]))
+	};
+
 	match opt.subcommand {
 		None => {
 			opt.run.base.init(&version)?;
@@ -61,7 +69,7 @@ pub fn run(version: VersionInfo) -> sc_cli::Result<()> {
 					service::kusama_runtime::RuntimeApi,
 					service::KusamaExecutor,
 					service::kusama_runtime::UncheckedExtrinsic,
-				>(config, opt.authority_discovery_enabled)
+				>(config, opt.authority_discovery_enabled, grandpa_pause)
 			} else {
 				info!("Native runtime: {}", service::PolkadotExecutor::native_version().runtime_version);
 
@@ -69,7 +77,7 @@ pub fn run(version: VersionInfo) -> sc_cli::Result<()> {
 					service::polkadot_runtime::RuntimeApi,
 					service::PolkadotExecutor,
 					service::polkadot_runtime::UncheckedExtrinsic,
-				>(config, opt.authority_discovery_enabled)
+				>(config, opt.authority_discovery_enabled, grandpa_pause)
 			}
 		},
 		Some(Subcommand::Base(cmd)) => {
@@ -123,6 +131,7 @@ pub fn run(version: VersionInfo) -> sc_cli::Result<()> {
 fn run_service_until_exit<R, D, E>(
 	config: service::Configuration,
 	authority_discovery_enabled: bool,
+	grandpa_pause: Option<(u32, u32)>,
 ) -> sc_cli::Result<()>
 where
 	R: ConstructRuntimeApi<Block, service::TFullClient<Block, R, D>>
@@ -151,7 +160,14 @@ where
 		_ =>
 			sc_cli::run_service_until_exit(
 				config,
-				|config| service::new_full::<R, D, E>(config, None, None, authority_discovery_enabled, 6000)
+				|config| service::new_full::<R, D, E>(
+					config,
+					None,
+					None,
+					authority_discovery_enabled,
+					6000,
+					grandpa_pause,
+				)
 					.map(|(s, _)| s),
 			),
 	}