Start finality relay spec-version guards for Rococo <> Wococo finality relays (#965)

* start finality relay guards

* comment

bridges/relays/bin-substrate/src/chains/rococo_headers_to_wococo.rs

@@ -21,7 +21,7 @@ use crate::finality_pipeline::{SubstrateFinalitySyncPipeline, SubstrateFinalityT
 use bp_header_chain::justification::GrandpaJustification;
 use codec::Encode;
 use relay_rococo_client::{Rococo, SyncHeader as RococoSyncHeader};
-use relay_substrate_client::{Chain, TransactionSignScheme};
+use relay_substrate_client::{Chain, Client, TransactionSignScheme};
 use relay_utils::metrics::MetricsParams;
 use relay_wococo_client::{SigningParams as WococoSigningParams, Wococo};
 use sp_core::{Bytes, Pair};
@@ -38,6 +38,13 @@ impl SubstrateFinalitySyncPipeline for RococoFinalityToWococo {
 		crate::chains::add_polkadot_kusama_price_metrics::<Self>(params)
 	}
 
+	fn start_relay_guards(target_client: &Client<Self::TargetChain>) {
+		relay_substrate_client::guard::abort_on_spec_version_change(
+			target_client.clone(),
+			bp_wococo::VERSION.spec_version,
+		)
+	}
+
 	fn transactions_author(&self) -> bp_wococo::AccountId {
 		(*self.target_sign.public().as_array_ref()).into()
 	}

bridges/relays/bin-substrate/src/chains/wococo_headers_to_rococo.rs

@@ -21,7 +21,7 @@ use crate::finality_pipeline::{SubstrateFinalitySyncPipeline, SubstrateFinalityT
 use bp_header_chain::justification::GrandpaJustification;
 use codec::Encode;
 use relay_rococo_client::{Rococo, SigningParams as RococoSigningParams};
-use relay_substrate_client::{Chain, TransactionSignScheme};
+use relay_substrate_client::{Chain, Client, TransactionSignScheme};
 use relay_utils::metrics::MetricsParams;
 use relay_wococo_client::{SyncHeader as WococoSyncHeader, Wococo};
 use sp_core::{Bytes, Pair};
@@ -38,6 +38,13 @@ impl SubstrateFinalitySyncPipeline for WococoFinalityToRococo {
 		crate::chains::add_polkadot_kusama_price_metrics::<Self>(params)
 	}
 
+	fn start_relay_guards(target_client: &Client<Self::TargetChain>) {
+		relay_substrate_client::guard::abort_on_spec_version_change(
+			target_client.clone(),
+			bp_rococo::VERSION.spec_version,
+		)
+	}
+
 	fn transactions_author(&self) -> bp_rococo::AccountId {
 		(*self.target_sign.public().as_array_ref()).into()
 	}

bridges/relays/bin-substrate/src/cli/relay_headers.rs

@@ -97,6 +97,7 @@ impl RelayHeaders {
 			let target_client = self.target.to_client::<Target>().await?;
 			let target_sign = self.target_sign.to_keypair::<Target>()?;
 			let metrics_params = Finality::customize_metrics(self.prometheus_params.into())?;
+			Finality::start_relay_guards(&target_client);
 
 			crate::finality_pipeline::run(
 				Finality::new(target_client.clone(), target_sign),

bridges/relays/bin-substrate/src/finality_pipeline.rs

@@ -46,6 +46,13 @@ pub trait SubstrateFinalitySyncPipeline: FinalitySyncPipeline {
 		Ok(params)
 	}
 
+	/// Start finality relay guards.
+	///
+	/// Different finality bridges may have different set of guards - e.g. on ephemeral chains we
+	/// don't need version guards, on test chains we don't care that much about relayer account
+	/// balance, ... So the implementation is left to the specific bridges.
+	fn start_relay_guards(_target_client: &Client<Self::TargetChain>) {}
+
 	/// Returns id of account that we're using to sign transactions at target chain.
 	fn transactions_author(&self) -> <Self::TargetChain as Chain>::AccountId;