Aviod iteration all the time to the beginning

bridges/modules/messages/src/lib.rs

@@ -640,18 +640,16 @@ pub mod pallet {
 
 				// collect message_nonces that were supposed to be pruned
 				let mut unpruned_message_nonces = Vec::new();
-				let mut nonce_to_check = expected_last_prunned_nonce;
-				loop {
+				const MAX_MESSAGES_ITERATION: u64 = 16;
+				let start_nonce =
+					expected_last_prunned_nonce.checked_sub(MAX_MESSAGES_ITERATION).unwrap_or(0);
+				for current_nonce in start_nonce..=expected_last_prunned_nonce {
+					// check a message for current_nonce
 					if OutboundMessages::<T, I>::contains_key(MessageKey {
 						lane_id,
-						nonce: nonce_to_check,
+						nonce: current_nonce,
 					}) {
-						unpruned_message_nonces.push(nonce_to_check);
-					}
-					if let Some(new_nonce_to_check) = nonce_to_check.checked_sub(One::one()) {
-						nonce_to_check = new_nonce_to_check;
-					} else {
-						break;
+						unpruned_message_nonces.push(current_nonce);
 					}
 				}
 

bridges/modules/messages/src/tests/pallet_tests.rs

@@ -38,14 +38,14 @@ use bp_runtime::{BasicOperatingMode, PreComputedSize, RangeInclusiveExt, Size};
 use bp_test_utils::generate_owned_bridge_module_tests;
 use codec::Encode;
 use frame_support::{
-	assert_noop, assert_ok,
+	assert_err, assert_noop, assert_ok,
 	dispatch::Pays,
 	storage::generator::{StorageMap, StorageValue},
 	weights::Weight,
 };
 use frame_system::{EventRecord, Pallet as System, Phase};
 use sp_core::Get;
-use sp_runtime::DispatchError;
+use sp_runtime::{BoundedVec, DispatchError};
 
 fn get_ready_for_events() {
 	System::<TestRuntime>::set_block_number(1);
@@ -983,3 +983,33 @@ fn maybe_outbound_lanes_count_returns_correct_value() {
 		Some(mock::ActiveOutboundLanes::get().len() as u32)
 	);
 }
+
+#[test]
+fn do_try_state_for_outbound_lanes_works() {
+	run_test(|| {
+		let lane_id = TEST_LANE_ID;
+
+		// setup delivered nonce 1
+		OutboundLanes::<TestRuntime>::insert(
+			lane_id,
+			OutboundLaneData {
+				oldest_unpruned_nonce: 2,
+				latest_received_nonce: 1,
+				latest_generated_nonce: 0,
+			},
+		);
+		// store message for nonce 1
+		OutboundMessages::<TestRuntime>::insert(
+			MessageKey { lane_id, nonce: 1 },
+			BoundedVec::default(),
+		);
+		assert_err!(
+			Pallet::<TestRuntime>::do_try_state(),
+			sp_runtime::TryRuntimeError::Other("Found unpruned lanes!")
+		);
+
+		// remove message for nonce 1
+		OutboundMessages::<TestRuntime>::remove(MessageKey { lane_id, nonce: 1 });
+		assert_ok!(Pallet::<TestRuntime>::do_try_state());
+	})
+}