Do not perform client update if consensus state already exists

crates/relayer/src/foreign_client.rs

@@ -123,7 +123,7 @@ define_error! {
                 height: Height,
             }
             |e| {
-                format_args!("client {} is already up-to-date with chain {}@{}",
+                format_args!("client {} is already up-to-date with chain {} at height {}",
                     e.client_id, e.chain_id, e.height)
             },
 
@@ -1131,6 +1131,24 @@ impl<DstChain: ChainHandle, SrcChain: ChainHandle> ForeignClient<DstChain, SrcCh
             }
         );
 
+        let consensus_state = self.dst_chain().query_consensus_state(
+            QueryConsensusStateRequest {
+                client_id: self.id().clone(),
+                consensus_height: target_height,
+                query_height: QueryHeight::Latest,
+            },
+            IncludeProof::No,
+        );
+
+        if let Ok((consensus_state, _)) = consensus_state {
+            debug!("consensus state already exists at height {target_height}, skipping update");
+            trace!(?consensus_state, "consensus state");
+
+            // If the client already stores a consensus state for the target height,
+            // there is no need to update the client
+            return Ok(vec![]);
+        }
+
         let src_application_latest_height = || {
             self.src_chain().query_latest_height().map_err(|e| {
                 ForeignClientError::client_create(
@@ -1149,6 +1167,7 @@ impl<DstChain: ChainHandle, SrcChain: ChainHandle> ForeignClient<DstChain, SrcCh
                     "dst_chain": self.dst_chain().id(),
                 }
             );
+
             // Wait for the source network to produce block(s) & reach `target_height`.
             while src_application_latest_height()? < target_height {
                 thread::sleep(Duration::from_millis(100));