From c6449fad59d0deeddfbd4b18481f4a30f01eb116 Mon Sep 17 00:00:00 2001
From: Chris Czub <chris@penumbralabs.xyz>
Date: Tue, 30 Apr 2024 16:22:23 -0400
Subject: [PATCH] Filter out fixed candidates from the recently accessed asset
 list

---
 .../dex/src/component/action_handler/swap.rs  | 10 ++++--
 .../dex/src/component/position_manager.rs     | 31 +++++++++++++++----
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/crates/core/component/dex/src/component/action_handler/swap.rs b/crates/core/component/dex/src/component/action_handler/swap.rs
index cbffd75b4d..86d4591c8c 100644
--- a/crates/core/component/dex/src/component/action_handler/swap.rs
+++ b/crates/core/component/dex/src/component/action_handler/swap.rs
@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use anyhow::{ensure, Result};
 use async_trait::async_trait;
 use cnidarium::StateWrite;
@@ -68,8 +70,12 @@ impl ActionHandler for Swap {
             .await;
 
         // Mark the assets for the swap's trading pair as accessed during this block.
-        state.add_recently_accessed_asset(swap.body.trading_pair.asset_1());
-        state.add_recently_accessed_asset(swap.body.trading_pair.asset_2());
+        let fixed_candidates = Arc::new(dex_params.fixed_candidates.clone());
+        state.add_recently_accessed_asset(
+            swap.body.trading_pair.asset_1(),
+            fixed_candidates.clone(),
+        );
+        state.add_recently_accessed_asset(swap.body.trading_pair.asset_2(), fixed_candidates);
 
         metrics::histogram!(crate::component::metrics::DEX_SWAP_DURATION)
             .record(swap_start.elapsed());
diff --git a/crates/core/component/dex/src/component/position_manager.rs b/crates/core/component/dex/src/component/position_manager.rs
index b34094c63c..b807815870 100644
--- a/crates/core/component/dex/src/component/position_manager.rs
+++ b/crates/core/component/dex/src/component/position_manager.rs
@@ -11,9 +11,12 @@ use penumbra_asset::{asset, Balance};
 use penumbra_proto::DomainType;
 use penumbra_proto::{StateReadProto, StateWriteProto};
 
-use crate::component::position_manager::{
-    base_liquidity_index::AssetByLiquidityIndex, inventory_index::PositionByInventoryIndex,
-    price_index::PositionByPriceIndex,
+use crate::component::{
+    dex::StateReadExt as _,
+    position_manager::{
+        base_liquidity_index::AssetByLiquidityIndex, inventory_index::PositionByInventoryIndex,
+        price_index::PositionByPriceIndex,
+    },
 };
 use crate::lp::Reserves;
 use crate::{
@@ -253,8 +256,15 @@ pub trait PositionManager: StateWrite + PositionRead {
 
         // Add the asset IDs from the new position's trading pair
         // to the candidate set for this block.
-        self.add_recently_accessed_asset(position.phi.pair.asset_1());
-        self.add_recently_accessed_asset(position.phi.pair.asset_2());
+        let routing_params = self.routing_params().await?;
+        self.add_recently_accessed_asset(
+            position.phi.pair.asset_1(),
+            routing_params.fixed_candidates.clone(),
+        );
+        self.add_recently_accessed_asset(
+            position.phi.pair.asset_2(),
+            routing_params.fixed_candidates,
+        );
 
         // Finally, record the new position state.
         self.record_proto(event::position_open(&position));
@@ -269,7 +279,11 @@ pub trait PositionManager: StateWrite + PositionRead {
     /// This ensures that assets associated with recently active positions
     /// will be eligible for arbitrage if mispriced positions are opened.
     #[tracing::instrument(level = "debug", skip_all)]
-    fn add_recently_accessed_asset(&mut self, asset_id: asset::Id) {
+    fn add_recently_accessed_asset(
+        &mut self,
+        asset_id: asset::Id,
+        fixed_candidates: Arc<Vec<asset::Id>>,
+    ) {
         let mut assets = self.recently_accessed_assets();
 
         // Limit the number of recently accessed assets to prevent blowing
@@ -278,6 +292,11 @@ pub trait PositionManager: StateWrite + PositionRead {
             return;
         }
 
+        // If the asset is already in the fixed candidate list, don't insert it.
+        if fixed_candidates.contains(&asset_id) {
+            return;
+        }
+
         assets.insert(asset_id);
         self.object_put(state_key::recently_accessed_assets(), assets);
     }