Collation fairness in backing subsystem

polkadot/node/core/backing/src/error.rs

@@ -108,6 +108,24 @@ pub enum Error {
 
 	#[error("Runtime API returned None for executor params")]
 	MissingExecutorParams,
+
+	#[error("No free slot in claim queue for candidate")]
+	NoFreeSlotInClaimQueue,
+
+	#[error("Failed to send claimed slots")]
+	SendClaimedSlots,
+
+	#[error("Falied to send `CanClaim` response")]
+	SendCanClaim,
+
+	#[error("ChainApiSubsystem channel closed before receipt")]
+	BlockHeader(#[source] oneshot::Canceled),
+
+	#[error("Can't get block header from ChainApiSubsystem")]
+	ChainApi(#[source] polkadot_node_subsystem::ChainApiError),
+
+	#[error("Block header not found for relay parent {0:?}")]
+	MissingBlockHeader(polkadot_primitives::Hash),
 }
 
 /// Utility for eating top level errors and log them.