polkadot-node-subsystems: ChainApiBackend added + polkadot-debug image version fixed (#2411)

The out-dated version (bad tag) of [polkadot
image](https://github.com/paritytech/polkadot-sdk/blob/ede4a362622dfa69eb167eaa876246b1289f4b41/.gitlab/pipeline/zombienet/cumulus.yml#L31)
([docker
info](https://hub.docker.com/layers/paritypr/polkadot-debug/master/images/sha256:adb1658052cf671b50c90d5cece5c7a131efa1a95978249bd5cb85a5ad654f7a?context=explore))
was used. This PR fixes this.

See also:
https://github.com/paritytech/polkadot-sdk/pull/2411#issuecomment-1822632724

Also adds an abstraction that allows asynchronous backends to be passed to `ChainApiSubsystem`
---------

Co-authored-by: Sebastian Kunert <skunert49@gmail.com>

polkadot/node/subsystem-types/Cargo.toml

@@ -17,6 +17,7 @@ polkadot-node-jaeger = { path = "../jaeger" }
 orchestra = { version = "0.3.3", default-features = false, features=["futures_channel"] }
 sc-network = { path = "../../../substrate/client/network" }
 sp-api = { path = "../../../substrate/primitives/api" }
+sp-blockchain = { path = "../../../substrate/primitives/blockchain" }
 sp-consensus-babe = { path = "../../../substrate/primitives/consensus/babe" }
 sp-authority-discovery = { path = "../../../substrate/primitives/authority-discovery" }
 sc-client-api = { path = "../../../substrate/client/api" }

polkadot/node/subsystem-types/src/lib.rs

@@ -40,7 +40,7 @@ pub mod errors;
 pub mod messages;
 
 mod runtime_client;
-pub use runtime_client::{DefaultSubsystemClient, RuntimeApiSubsystemClient};
+pub use runtime_client::{ChainApiBackend, DefaultSubsystemClient, RuntimeApiSubsystemClient};
 
 pub use jaeger::*;
 pub use polkadot_node_jaeger as jaeger;

polkadot/node/subsystem-types/src/runtime_client.rs

@@ -18,17 +18,70 @@ use async_trait::async_trait;
 use polkadot_primitives::{
 	async_backing, runtime_api::ParachainHost, slashing, vstaging, Block, BlockNumber,
 	CandidateCommitments, CandidateEvent, CandidateHash, CommittedCandidateReceipt, CoreState,
-	DisputeState, ExecutorParams, GroupRotationInfo, Hash, Id, InboundDownwardMessage,
+	DisputeState, ExecutorParams, GroupRotationInfo, Hash, Header, Id, InboundDownwardMessage,
 	InboundHrmpMessage, OccupiedCoreAssumption, PersistedValidationData, PvfCheckStatement,
 	ScrapedOnChainVotes, SessionIndex, SessionInfo, ValidationCode, ValidationCodeHash,
 	ValidatorId, ValidatorIndex, ValidatorSignature,
 };
+use sc_client_api::HeaderBackend;
 use sc_transaction_pool_api::OffchainTransactionPoolFactory;
-use sp_api::{ApiError, ApiExt, ProvideRuntimeApi};
+use sp_api::{ApiError, ApiExt, HeaderT, NumberFor, ProvideRuntimeApi};
 use sp_authority_discovery::AuthorityDiscoveryApi;
+use sp_blockchain::Info;
 use sp_consensus_babe::{BabeApi, Epoch};
 use std::{collections::BTreeMap, sync::Arc};
 
+/// Offers header utilities.
+///
+/// This is a async wrapper trait for ['HeaderBackend'] to be used with the
+/// `ChainApiSubsystem`.
+// This trait was introduced to suit the needs of collators. Depending on their operating mode, they
+// might not have a client of the relay chain that can supply a synchronous HeaderBackend
+// implementation.
+#[async_trait]
+pub trait ChainApiBackend: Send + Sync {
+	/// Get block header. Returns `None` if block is not found.
+	async fn header(&self, hash: Hash) -> sp_blockchain::Result<Option<Header>>;
+	/// Get blockchain info.
+	async fn info(&self) -> sp_blockchain::Result<Info<Block>>;
+	/// Get block number by hash. Returns `None` if the header is not in the chain.
+	async fn number(
+		&self,
+		hash: Hash,
+	) -> sp_blockchain::Result<Option<<Header as HeaderT>::Number>>;
+	/// Get block hash by number. Returns `None` if the header is not in the chain.
+	async fn hash(&self, number: NumberFor<Block>) -> sp_blockchain::Result<Option<Hash>>;
+}
+
+#[async_trait]
+impl<T> ChainApiBackend for T
+where
+	T: HeaderBackend<Block>,
+{
+	/// Get block header. Returns `None` if block is not found.
+	async fn header(&self, hash: Hash) -> sp_blockchain::Result<Option<Header>> {
+		HeaderBackend::header(self, hash)
+	}
+
+	/// Get blockchain info.
+	async fn info(&self) -> sp_blockchain::Result<Info<Block>> {
+		Ok(HeaderBackend::info(self))
+	}
+
+	/// Get block number by hash. Returns `None` if the header is not in the chain.
+	async fn number(
+		&self,
+		hash: Hash,
+	) -> sp_blockchain::Result<Option<<Header as HeaderT>::Number>> {
+		HeaderBackend::number(self, hash)
+	}
+
+	/// Get block hash by number. Returns `None` if the header is not in the chain.
+	async fn hash(&self, number: NumberFor<Block>) -> sp_blockchain::Result<Option<Hash>> {
+		HeaderBackend::hash(self, number)
+	}
+}
+
 /// Exposes all runtime calls that are used by the runtime API subsystem.
 #[async_trait]
 pub trait RuntimeApiSubsystemClient {