Snowbridge V2: Add OnNewCommitment hook to outbound-queue pallet

bridges/snowbridge/pallets/outbound-queue-v2/src/lib.rs

@@ -97,7 +97,7 @@ use sp_runtime::{
 	DigestItem,
 };
 use sp_std::prelude::*;
-pub use types::{PendingOrder, ProcessMessageOriginOf};
+pub use types::{OnNewCommitment, PendingOrder, ProcessMessageOriginOf};
 pub use weights::WeightInfo;
 use xcm::prelude::NetworkId;
 
@@ -137,6 +137,9 @@ pub mod pallet {
 		#[pallet::constant]
 		type MaxMessagesPerBlock: Get<u32>;
 
+		/// Hook that is called whenever there is a new commitment.
+		type OnNewCommitment: OnNewCommitment;
+
 		/// Convert a weight value into a deductible fee based.
 		type WeightToFee: WeightToFee<Balance = Self::Balance>;
 
@@ -321,6 +324,8 @@ pub mod pallet {
 			// Insert merkle root into the header digest
 			<frame_system::Pallet<T>>::deposit_log(digest_item);
 
+			T::OnNewCommitment::on_new_commitment(root);
+
 			Self::deposit_event(Event::MessagesCommitted { root, count });
 		}
 

bridges/snowbridge/pallets/outbound-queue-v2/src/mock.rs

@@ -116,6 +116,7 @@ impl crate::Config for Test {
 	type EthereumNetwork = EthereumNetwork;
 	type RewardKind = BridgeReward;
 	type DefaultRewardKind = DefaultMyRewardKind;
+	type OnNewCommitment = ();
 	#[cfg(feature = "runtime-benchmarks")]
 	type Helper = Test;
 }

bridges/snowbridge/pallets/outbound-queue-v2/src/types.rs

@@ -5,6 +5,7 @@ use codec::{Decode, Encode, MaxEncodedLen};
 use frame_support::traits::ProcessMessage;
 use scale_info::TypeInfo;
 pub use snowbridge_merkle_tree::MerkleProof;
+use sp_core::H256;
 use sp_runtime::RuntimeDebug;
 use sp_std::prelude::*;
 
@@ -21,3 +22,12 @@ pub struct PendingOrder<BlockNumber> {
 	#[codec(compact)]
 	pub fee: u128,
 }
+
+/// Hook that will be called when a new message commitment is constructed.
+pub trait OnNewCommitment {
+	fn on_new_commitment(commitment: H256);
+}
+
+impl OnNewCommitment for () {
+	fn on_new_commitment(_commitment: H256) {}
+}

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/bridge_to_ethereum_config.rs

@@ -192,6 +192,8 @@ impl snowbridge_pallet_outbound_queue_v2::Config for Runtime {
 	type RewardKind = BridgeReward;
 	type DefaultRewardKind = SnowbridgeReward;
 	type RewardPayment = BridgeRelayers;
+	// No consumers of this notifier on Bridge Hub.
+	type OnNewCommitment = ();
 	#[cfg(feature = "runtime-benchmarks")]
 	type Helper = Runtime;
 }

prdoc/pr_8053.prdoc

@@ -0,0 +1,10 @@
+title: Add `OnNewCommitment` hook to outbound-queue pallet
+doc:
+- audience: Runtime Dev
+  description: |-
+    Add a simple hook to outbound-queue-v2 pallet which allows to perform actions whenever there is a new commitment.
+crates: 
+- name: snowbridge-pallet-outbound-queue-v2
+  bump: major
+- name: bridge-hub-westend-runtime
+  bump: major