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.
## 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 <[email protected]>
Co-authored-by: 
Liam Aharon <[email protected]>
Co-authored-by: 
joe petrowski <[email protected]>
Co-authored-by: 
Kian Paimani <[email protected]>
Co-authored-by: command-bot <>