Function cumulus_client_service::start_relay_chain_tasks

pub fn start_relay_chain_tasks<Block, Client, Backend, RCInterface>(
    _: StartRelayChainTasksParams<'_, Block, Client, RCInterface>,
) -> Result<()>
where
    Block: BlockT,
    Client: Finalizer<Block, Backend> + UsageProvider<Block> + Send + Sync + BlockBackend<Block> + BlockchainEvents<Block> + 'static,
    for<'a> &'a Client: BlockImport<Block>,
    Backend: BackendT<Block> + 'static,
    RCInterface: RelayChainInterface + Clone + 'static,

Start necessary consensus tasks related to the relay chain.

Parachain nodes need to track the state of the relay chain and use the relay chain’s data availability service to fetch blocks if they don’t arrive via the normal p2p layer (i.e. when authors withhold their blocks deliberately).

This function spawns work for those side tasks.