Use Message Queue as DMP and XCMP dispatch queue (#1246)

(imported from https://github.com/paritytech/cumulus/pull/2157)

## Changes

This MR refactores the XCMP, Parachains System and DMP pallets to use
the [MessageQueue](https://github.com/paritytech/substrate/pull/12485)
for delayed execution of incoming messages. The DMP pallet is entirely
replaced by the MQ and thereby removed. This allows for PoV-bounded
execution and resolves a number of issues that stem from the current
work-around.

All System Parachains adopt this change.  
The most important changes are in `primitives/core/src/lib.rs`,
`parachains/common/src/process_xcm_message.rs`,
`pallets/parachain-system/src/lib.rs`, `pallets/xcmp-queue/src/lib.rs`
and the runtime configs.

### DMP Queue Pallet

The pallet got removed and its logic refactored into parachain-system.
Overweight message management can be done directly through the MQ
pallet.

Final undeployment migrations are provided by
`cumulus_pallet_dmp_queue::UndeployDmpQueue` and `DeleteDmpQueue` that
can be configured with an aux config trait like:

```rust
parameter_types! {
	pub const DmpQueuePalletName: &'static str = \"DmpQueue\" < CHANGE ME;
	pub const RelayOrigin: AggregateMessageOrigin = AggregateMessageOrigin::Parent;
}

impl cumulus_pallet_dmp_queue::MigrationConfig for Runtime {
	type PalletName = DmpQueuePalletName;
	type DmpHandler = frame_support::traits::EnqueueWithOrigin<MessageQueue, RelayOrigin>;
	type DbWeight = <Runtime as frame_system::Config>::DbWeight;
}

// And adding them to your Migrations tuple:
pub type Migrations = (
	...
	cumulus_pallet_dmp_queue::UndeployDmpQueue<Runtime>,
	cumulus_pallet_dmp_queue::DeleteDmpQueue<Runtime>,
);
```

### XCMP Queue pallet

Removed all dispatch queue functionality. Incoming XCMP messages are now
either: Immediately handled if they are Signals, enqueued into the MQ
pallet otherwise.

New config items for the XCMP queue pallet:
```rust
/// The actual queue implementation that retains the messages for later processing.
type XcmpQueue: EnqueueMessage<ParaId>;

/// How a XCM over HRMP from a sibling parachain should be processed.
type XcmpProcessor: ProcessMessage<Origin = ParaId>;

/// The maximal number of suspended XCMP channels at the same time.
#[pallet::constant]
type MaxInboundSuspended: Get<u32>;
```

How to configure those:

```rust
// Use the MessageQueue pallet to store messages for later processing. The `TransformOrigin` is needed since
// the MQ pallet itself operators on `AggregateMessageOrigin` but we want to enqueue `ParaId`s.
type XcmpQueue = TransformOrigin<MessageQueue, AggregateMessageOrigin, ParaId, ParaIdToSibling>;

// Process XCMP messages from siblings. This is type-safe to only accept `ParaId`s. They will be dispatched
// with origin `Junction::Sibling(…)`.
type XcmpProcessor = ProcessFromSibling<
	ProcessXcmMessage<
		AggregateMessageOrigin,
		xcm_executor::XcmExecutor<xcm_config::XcmConfig>,
		RuntimeCall,
	>,
>;

// Not really important what to choose here. Just something larger than the maximal number of channels.
type MaxInboundSuspended = sp_core::ConstU32<1_000>;
```

The `InboundXcmpStatus` storage item was replaced by
`InboundXcmpSuspended` since it now only tracks inbound queue suspension
and no message indices anymore.

Now only sends the most recent channel `Signals`, as all prio ones are
out-dated anyway.

### Parachain System pallet

For `DMP` messages instead of forwarding them to the `DMP` pallet, it
now pushes them to the configured `DmpQueue`. The message processing
which was triggered in `set_validation_data` is now being done by the MQ
pallet `on_initialize`.

XCMP messages are still handed off to the `XcmpMessageHandler`
(XCMP-Queue pallet) - no change here.

New config items for the parachain system pallet:
```rust
/// Queues inbound downward messages for delayed processing. 
///
/// Analogous to the `XcmpQueue` of the XCMP queue pallet.
type DmpQueue: EnqueueMessage<AggregateMessageOrigin>;
``` 

How to configure:
```rust
/// Use the MQ pallet to store DMP messages for delayed processing.
type DmpQueue = MessageQueue;
``` 

## Message Flow

The flow of messages on the parachain side. Messages come in from the
left via the `Validation Data` and finally end up at the `Xcm Executor`
on the right.

![Untitled
(1)](https://github.com/paritytech/cumulus/assets/10380170/6cf8b377-88c9-4aed-96df-baace266e04d)

## Further changes

- Bumped the default suspension, drop and resume thresholds in
`QueueConfigData::default()`.
- `XcmpQueue::{suspend_xcm_execution, resume_xcm_execution}` errors when
they would be a noop.
- Properly validate the `QueueConfigData` before setting it.
- Marked weight files as auto-generated so they wont auto-expand in the
MR files view.
- Move the `hypothetical` asserts to `frame_support` under the name
`experimental_hypothetically`

Questions:
- [ ] What about the ugly `#[cfg(feature = \"runtime-benchmarks\")]` in
the runtimes? Not sure how to best fix. Just having them like this makes
tests fail that rely on the real message processor when the feature is
enabled.
- [ ] Need a good weight for `MessageQueueServiceWeight`. The scheduler
already takes 80% so I put it to 10% but that is quite low.

TODO:
- [x] Remove c&p code after
https://github.com/paritytech/polkadot/pull/6271
- [x] Use `HandleMessage` once it is public in Substrate
- [x] fix `runtime-benchmarks` feature
https://github.com/paritytech/polkadot/pull/6966
- [x] Benchmarks
- [x] Tests
- [ ] Migrate `InboundXcmpStatus` to `InboundXcmpSuspended`
- [x] Possibly cleanup Migrations (DMP+XCMP)
- [x] optional: create `TransformProcessMessageOrigin` in Substrate and
replace `ProcessFromSibling`
- [ ] Rerun weights on ref HW

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: command-bot <>

substrate/frame/support/src/lib.rs

@@ -51,7 +51,9 @@ pub mod __private {
 	pub use sp_metadata_ir as metadata_ir;
 	#[cfg(feature = "std")]
 	pub use sp_runtime::{bounded_btree_map, bounded_vec};
-	pub use sp_runtime::{traits::Dispatchable, RuntimeDebug, StateVersion};
+	pub use sp_runtime::{
+		traits::Dispatchable, DispatchError, RuntimeDebug, StateVersion, TransactionOutcome,
+	};
 	#[cfg(feature = "std")]
 	pub use sp_state_machine::BasicExternalities;
 	pub use sp_std;
@@ -781,6 +783,31 @@ macro_rules! assert_error_encoded_size {
 	} => {};
 }
 
+/// Do something hypothetically by rolling back any changes afterwards.
+///
+/// Returns the original result of the closure.
+#[macro_export]
+#[cfg(feature = "experimental")]
+macro_rules! hypothetically {
+	( $e:expr ) => {
+		$crate::storage::transactional::with_transaction(|| -> $crate::__private::TransactionOutcome<Result<_, $crate::__private::DispatchError>> {
+			$crate::__private::TransactionOutcome::Rollback(Ok($e))
+		},
+		).expect("Always returning Ok; qed")
+	};
+}
+
+/// Assert something to be *hypothetically* `Ok`, without actually committing it.
+///
+/// Reverts any storage changes made by the closure.
+#[macro_export]
+#[cfg(feature = "experimental")]
+macro_rules! hypothetically_ok {
+	($e:expr $(, $args:expr)* $(,)?) => {
+		$crate::assert_ok!($crate::hypothetically!($e) $(, $args)*);
+	};
+}
+
 #[doc(hidden)]
 pub use serde::{Deserialize, Serialize};
 

substrate/frame/support/src/traits.rs

@@ -113,7 +113,8 @@ pub use preimages::{Bounded, BoundedInline, FetchResult, QueryPreimage, StorePre
 mod messages;
 pub use messages::{
 	EnqueueMessage, EnqueueWithOrigin, ExecuteOverweightError, HandleMessage, NoopServiceQueues,
-	ProcessMessage, ProcessMessageError, QueuePausedQuery, ServiceQueues, TransformOrigin,
+	ProcessMessage, ProcessMessageError, QueueFootprint, QueuePausedQuery, ServiceQueues,
+	TransformOrigin,
 };
 
 mod safe_mode;

substrate/frame/support/src/traits/messages.rs

@@ -116,6 +116,15 @@ impl<OverweightAddr> ServiceQueues for NoopServiceQueues<OverweightAddr> {
 	}
 }
 
+/// The resource footprint of a queue.
+#[derive(Default, Copy, Clone, Eq, PartialEq, RuntimeDebug)]
+pub struct QueueFootprint {
+	/// The number of pages in the queue (including overweight pages).
+	pub pages: u32,
+	/// The storage footprint of the queue (including overweight messages).
+	pub storage: Footprint,
+}
+
 /// Can enqueue messages for multiple origins.
 pub trait EnqueueMessage<Origin: MaxEncodedLen> {
 	/// The maximal length any enqueued message may have.
@@ -134,7 +143,7 @@ pub trait EnqueueMessage<Origin: MaxEncodedLen> {
 	fn sweep_queue(origin: Origin);
 
 	/// Return the state footprint of the given queue.
-	fn footprint(origin: Origin) -> Footprint;
+	fn footprint(origin: Origin) -> QueueFootprint;
 }
 
 impl<Origin: MaxEncodedLen> EnqueueMessage<Origin> for () {
@@ -146,8 +155,8 @@ impl<Origin: MaxEncodedLen> EnqueueMessage<Origin> for () {
 	) {
 	}
 	fn sweep_queue(_: Origin) {}
-	fn footprint(_: Origin) -> Footprint {
-		Footprint::default()
+	fn footprint(_: Origin) -> QueueFootprint {
+		QueueFootprint::default()
 	}
 }
 
@@ -173,7 +182,7 @@ impl<E: EnqueueMessage<O>, O: MaxEncodedLen, N: MaxEncodedLen, C: Convert<N, O>>
 		E::sweep_queue(C::convert(origin));
 	}
 
-	fn footprint(origin: N) -> Footprint {
+	fn footprint(origin: N) -> QueueFootprint {
 		E::footprint(C::convert(origin))
 	}
 }
@@ -195,7 +204,7 @@ pub trait HandleMessage {
 	fn sweep_queue();
 
 	/// Return the state footprint of the queue.
-	fn footprint() -> Footprint;
+	fn footprint() -> QueueFootprint;
 }
 
 /// Adapter type to transform an [`EnqueueMessage`] with an origin into a [`HandleMessage`] impl.
@@ -220,7 +229,7 @@ where
 		E::sweep_queue(O::get());
 	}
 
-	fn footprint() -> Footprint {
+	fn footprint() -> QueueFootprint {
 		E::footprint(O::get())
 	}
 }