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Use Message Queue as DMP and XCMP dispatch queue (#1246)
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(imported from paritytech/cumulus#2157)

## Changes

This MR refactores the XCMP, Parachains System and DMP pallets to use
the [MessageQueue](paritytech/substrate#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
paritytech/polkadot#6271
- [x] Use `HandleMessage` once it is public in Substrate
- [x] fix `runtime-benchmarks` feature
paritytech/polkadot#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 <>
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39 changes: 33 additions & 6 deletions Cargo.lock

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36 changes: 25 additions & 11 deletions cumulus/pallets/dmp-queue/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -3,19 +3,24 @@ name = "cumulus-pallet-dmp-queue"
version = "0.1.0"
authors.workspace = true
edition.workspace = true
repository.workspace = true
description = "Migrates messages from the old DMP queue pallet."
license = "Apache-2.0"

[package.metadata.docs.rs]
targets = ["x86_64-unknown-linux-gnu"]

[dependencies]
codec = { package = "parity-scale-codec", version = "3.0.0", features = [ "derive" ], default-features = false }
codec = { package = "parity-scale-codec", version = "3.0.0", default-features = false, features = ["derive"] }
log = { version = "0.4.20", default-features = false }
scale-info = { version = "2.10.0", default-features = false, features = ["derive"] }

# Substrate
frame-support = { path = "../../../substrate/frame/support", default-features = false}
frame-system = { path = "../../../substrate/frame/system", default-features = false}
sp-io = { path = "../../../substrate/primitives/io", default-features = false}
sp-runtime = { path = "../../../substrate/primitives/runtime", default-features = false}
sp-std = { path = "../../../substrate/primitives/std", default-features = false}
frame-benchmarking = { path = "../../../substrate/frame/benchmarking", default-features = false, optional = true }
frame-support = { path = "../../../substrate/frame/support", default-features = false }
frame-system = { path = "../../../substrate/frame/system", default-features = false }
sp-std = { path = "../../../substrate/primitives/std", default-features = false }
sp-runtime = { path = "../../../substrate/primitives/runtime", default-features = false }
sp-io = { path = "../../../substrate/primitives/io", default-features = false }

# Polkadot
xcm = { package = "staging-xcm", path = "../../../polkadot/xcm", default-features = false}
Expand All @@ -24,25 +29,34 @@ xcm = { package = "staging-xcm", path = "../../../polkadot/xcm", default-feature
cumulus-primitives-core = { path = "../../primitives/core", default-features = false }

[dev-dependencies]
sp-core = { path = "../../../substrate/primitives/core", default-features = false}
sp-version = { path = "../../../substrate/primitives/version", default-features = false}
sp-core = { path = "../../../substrate/primitives/core" }
sp-tracing = { path = "../../../substrate/primitives/tracing" }

[features]
default = [ "std" ]

std = [
"codec/std",
"cumulus-primitives-core/std",
"frame-benchmarking?/std",
"frame-support/std",
"frame-system/std",
"log/std",
"scale-info/std",
"sp-core/std",
"sp-io/std",
"sp-runtime/std",
"sp-std/std",
"sp-version/std",
"xcm/std",
]

runtime-benchmarks = [
"cumulus-primitives-core/runtime-benchmarks",
"frame-benchmarking/runtime-benchmarks",
"frame-support/runtime-benchmarks",
"frame-system/runtime-benchmarks",
"sp-runtime/runtime-benchmarks",
]

try-runtime = [
"frame-support/try-runtime",
"frame-system/try-runtime",
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