Fix Asset Hub collator crashing when starting from genesis

[georgepisaltu]

Fixes #1566

Description

When running polkadot-parachain --chain asset-hub-* with no DB, the node would crash because it would try to access Aura API which wasn't available in the genesis shell runtime that Asset Hub started with. More details on the issue here.

This PR makes the node start with a relay chain driven consensus which doesn't call into AuraApi::slot_duration, then after the API becomes available (after the runtime is upgraded to the proper Asset Hub), it uses the Aura consensus.

Checklist

• My PR includes a detailed description as outlined in the "Description" section above
• My PR follows the labeling requirements of this project (at minimum one label for T
  required)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[bkchr]

Generally looking good, but some of the details need to improve.

[bkchr]

Suggested change

	let parachain_inherent = parachain_inherent.ok_or_else(|| {
	Box::<dyn std::error::Error + Send + Sync>::from(
	"Failed to create parachain inherent",
	)
	})?;
	Ok(parachain_inherent)
	parachain_inherent.ok_or_else(|| {
	Box::<dyn std::error::Error + Send + Sync>::from(
	"Failed to create parachain inherent",
	)
	})

[bkchr]

Suggested change

	let collation = {
	let last_head_hash = match collator
	.header_hash(request.persisted_validation_data().clone())
	{
	Some(header_hash) => header_hash,
	None => {
	request.complete(None);
	continue
	},
	};
	// Check if we have upgraded to an Aura compatible runtime and transition if
	// necessary.
	if client
	.runtime_api()
	.has_api::<dyn AuraApi<Block, AuraId>>(last_head_hash)
	.unwrap_or(false)
	{
	// Respond to this request before transitioning to Aura.
	request.complete(None);
	break
	}
	collator
	.clone()
	.produce_candidate(
	*request.relay_parent(),
	request.persisted_validation_data().clone(),
	)
	.await
	};
	request.complete(collation);
	let last_head_hash = match collator
	.header_hash(request.persisted_validation_data().clone())
	{
	Some(header_hash) => header_hash,
	None => {
	request.complete(None);
	continue
	},
	};
	// Check if we have upgraded to an Aura compatible runtime and transition if
	// necessary.
	if client
	.runtime_api()
	.has_api::<dyn AuraApi<Block, AuraId>>(last_head_hash)
	.unwrap_or(false)
	{
	// Respond to this request before transitioning to Aura.
	request.complete(None);
	break
	}
	request.complete(None);

[bkchr]

No need to try to produce any blocks.

[bkchr]

We actually don't need all of this code. Just decode the header manually and then check if the runtime api is there.

[georgepisaltu]

Done.

[bkchr]

Actually revert all the changes in this file.

[georgepisaltu]

Done.

[bkchr]

Please fix the last issues and then you can merge it! Ty!

[bkchr]

Suggested change

	if !collator_service.check_block_status(last_head_hash, &last_header) {
	request.complete(None);
	continue
	}

No need to do this.

[bkchr]

No unwrap. Please print the error and return.

[georgepisaltu]

Good catch, I forgot about this.

[bkchr]

Suggested change

	spawner.spawn("cumulus-asset-hub-collator", None, collation_future);
	spawner.spawn_essential("cumulus-asset-hub-collator", None, collation_future);

[bkchr]

Suggested change

	let spawner = task_manager.spawn_handle();
	let spawner = task_manager.spawn_essential_handle();