store latest messaging height

pallet-ismp/rpc/src/lib.rs

@@ -127,6 +127,10 @@ where
     #[method(name = "ismp_queryStateMachineLatestHeight")]
     fn query_state_machine_latest_height(&self, id: StateMachineId) -> Result<u64>;
 
+    /// Query the most recent height at which we've processed requests for a state machine
+    #[method(name = "ismp_queryLatestMessagingHeight")]
+    fn query_latest_messaging_height(&self, id: StateMachineId) -> Result<u64>;
+
     /// Query ISMP Events that were deposited in a series of blocks
     /// Using String keys because HashMap fails to deserialize when key is not a String
     #[method(name = "ismp_queryEvents")]
@@ -390,4 +394,12 @@ where
         }
         Ok(events)
     }
+
+    fn query_latest_messaging_height(&self, id: StateMachineId) -> Result<u64> {
+        let api = self.client.runtime_api();
+        let at = self.client.info().best_hash;
+        api.latest_messaging_height(at, id).ok().flatten().ok_or_else(|| {
+            runtime_error_into_rpc_error("Error fetching latest state machine height")
+        })
+    }
 }

pallet-ismp/runtime-api/src/lib.rs

@@ -60,6 +60,9 @@ sp_api::decl_runtime_apis! {
         /// Return the latest height of the state machine
         fn latest_state_machine_height(id: StateMachineId) -> Option<u64>;
 
+        /// Return the most recent height we've processed requests for a state machine
+        fn latest_messaging_height(id: StateMachineId) -> Option<u64>;
+
         /// Get Request Leaf Indices
         fn get_request_leaf_indices(leaf_queries: Vec<LeafIndexQuery>) -> Vec<LeafIndex>;
 

pallet-ismp/src/lib.rs

@@ -65,7 +65,7 @@ use ismp_primitives::{
     mmr::{DataOrHash, Leaf, LeafIndex, NodeIndex},
     LeafIndexQuery,
 };
-use ismp_rs::{host::IsmpHost, messaging::Message};
+use ismp_rs::{consensus::StateMachineHeight, host::IsmpHost, messaging::Message};
 pub use pallet::*;
 use sp_runtime::RuntimeDebug;
 use sp_std::prelude::*;
@@ -170,10 +170,16 @@ pub mod pallet {
     /// Holds a map of state machines to the height at which they've been frozen due to byzantine
     /// behaviour
     #[pallet::storage]
-    #[pallet::getter(fn frozen_heights)]
+    #[pallet::getter(fn latest_messaging_heights)]
     pub type FrozenHeights<T: Config> =
         StorageMap<_, Blake2_128Concat, StateMachineId, u64, OptionQuery>;
 
+    /// Holds a map of state machines to the latest height we've processed requests for
+    #[pallet::storage]
+    #[pallet::getter(fn frozen_heights)]
+    pub type LatestMessagingHeight<T: Config> =
+        StorageMap<_, Blake2_128Concat, StateMachineId, u64, ValueQuery>;
+
     /// A mapping of ConsensusStateId to ConsensusClientId
     #[pallet::storage]
     pub type ConsensusStateClient<T: Config> =
@@ -468,7 +474,7 @@ impl<T: Config> Pallet<T> {
         let mut errors: Vec<HandlingError> = vec![];
         let total_weight = get_weight::<T>(&messages);
         for message in messages {
-            match handle_incoming_message(&host, message) {
+            match handle_incoming_message(&host, message.clone()) {
                 Ok(MessageResult::ConsensusMessage(res)) => {
                     // check if this is a trusted state machine
                     let is_trusted_state_machine = host
@@ -508,9 +514,25 @@ impl<T: Config> Pallet<T> {
                     }
                 }
                 Ok(MessageResult::Response(res)) => {
+                    let StateMachineHeight { id, height } = match message {
+                        Message::Request(ref request) => request.proof.height.clone(),
+                        _ => unreachable!(),
+                    };
+                    // update the messaging heights
+                    if LatestMessagingHeight::<T>::get(&id) > height {
+                        LatestMessagingHeight::<T>::insert(id, height);
+                    }
                     debug!(target: "ismp-modules", "Module Callback Results {:?}", ModuleCallbackResult::Response(res));
                 }
                 Ok(MessageResult::Request(res)) => {
+                    let StateMachineHeight { id, height } = match message {
+                        Message::Request(ref request) => request.proof.height.clone(),
+                        _ => unreachable!(),
+                    };
+                    // update the messaging heights
+                    if LatestMessagingHeight::<T>::get(&id) > height {
+                        LatestMessagingHeight::<T>::insert(id, height);
+                    }
                     debug!(target: "ismp-modules", "Module Callback Results {:?}", ModuleCallbackResult::Request(res));
                 }
                 Ok(MessageResult::Timeout(res)) => {