client/beefy: fail initialization if state unavailable

client/beefy/src/lib.rs

@@ -376,17 +376,8 @@ where
 			break state
 		}
 
-		// Check if we should move up the chain.
-		let parent_hash = *header.parent_hash();
-		if *header.number() == One::one() ||
-			runtime
-				.runtime_api()
-				.validator_set(&BlockId::hash(parent_hash))
-				.ok()
-				.flatten()
-				.is_none()
-		{
-			// We've reached pallet genesis, initialize voter here.
+		if *header.number() == One::one() {
+			// We've reached chain genesis, initialize voter here.
 			let genesis_num = *header.number();
 			let genesis_set = expect_validator_set(runtime, BlockId::hash(header.hash()))
 				.and_then(genesis_set_sanity_check)?;
@@ -407,6 +398,19 @@ where
 			sessions.push_front(Rounds::new(*header.number(), active));
 		}
 
+		// Check if state is still available if we move up the chain.
+		let parent_hash = *header.parent_hash();
+		runtime
+			.runtime_api()
+			.validator_set(&BlockId::hash(parent_hash))
+			.ok()
+			.flatten()
+			.ok_or_else(|| {
+				let msg = format!("{}. Could not initialize BEEFY voter.", parent_hash);
+				error!(target: "beefy", "🥩 {}", msg);
+				ClientError::Consensus(sp_consensus::Error::StateUnavailable(msg))
+			})?;
+
 		// Move up the chain.
 		header = blockchain.expect_header(BlockId::Hash(parent_hash))?;
 	};