dex: add max_positions_per_pair to parameters

crates/core/app/src/params/change.rs

@@ -25,7 +25,6 @@ impl AppParameters {
         new.check_valid()?;
         // TODO: move the checks below into their respective components.
         // Tracked by #3593
-
         let AppParameters {
             chain_id,
             community_pool_params:
@@ -75,6 +74,7 @@ impl AppParameters {
                     is_enabled: _,
                     fixed_candidates: _,
                     max_hops: _,
+                    max_positions_per_pair: _,
                 },
             // IMPORTANT: Don't use `..` here! We want to ensure every single field is verified!
         } = self;
@@ -169,6 +169,7 @@ impl AppParameters {
                     is_enabled: _,
                     fixed_candidates: _,
                     max_hops: _,
+                    max_positions_per_pair: _,
                 },
             // IMPORTANT: Don't use `..` here! We want to ensure every single field is verified!
         } = self;
@@ -244,6 +245,7 @@ impl AppParameters {
                 *min_validator_stake >= 1_000_000u128.into(),
                 "the minimum validator stake must be at least 1penumbra",
             ),
+            // TODO(erwan): add a `max_positions_per_pair` check
         ])
     }
 

crates/core/component/dex/src/params.rs

@@ -10,6 +10,7 @@ pub struct DexParameters {
     pub is_enabled: bool,
     pub fixed_candidates: Vec<asset::Id>,
     pub max_hops: u32,
+    pub max_positions_per_pair: u32,
 }
 
 impl DomainType for DexParameters {
@@ -28,6 +29,7 @@ impl TryFrom<pb::DexParameters> for DexParameters {
                 .map(|id| id.try_into())
                 .collect::<Result<_, _>>()?,
             max_hops: msg.max_hops,
+            max_positions_per_pair: msg.max_positions_per_pair,
         })
     }
 }
@@ -42,6 +44,7 @@ impl From<DexParameters> for pb::DexParameters {
                 .map(Into::into)
                 .collect(),
             max_hops: params.max_hops,
+            max_positions_per_pair: params.max_positions_per_pair,
         }
     }
 }
@@ -63,6 +66,8 @@ impl Default for DexParameters {
                 cache.get_unit("test_btc").unwrap().id(),
             ],
             max_hops: 4,
+            // TODO(erwan): setting this to 10 for testing.
+            max_positions_per_pair: 10,
         }
     }
 }

crates/proto/src/gen/penumbra.core.component.dex.v1.rs

@@ -1509,6 +1509,11 @@ pub struct DexParameters {
     /// The number of hops to traverse while routing from A to B.
     #[prost(uint32, tag = "3")]
     pub max_hops: u32,
+    /// The maximum number of positions per trading pair.
+    /// If this number is exceeded, positions with the least
+    /// inventory get evicted from the DEX.
+    #[prost(uint32, tag = "4")]
+    pub max_positions_per_pair: u32,
 }
 impl ::prost::Name for DexParameters {
     const NAME: &'static str = "DexParameters";

crates/proto/src/gen/penumbra.core.component.dex.v1.serde.rs

@@ -1052,6 +1052,9 @@ impl serde::Serialize for DexParameters {
         if self.max_hops != 0 {
             len += 1;
         }
+        if self.max_positions_per_pair != 0 {
+            len += 1;
+        }
         let mut struct_ser = serializer.serialize_struct("penumbra.core.component.dex.v1.DexParameters", len)?;
         if self.is_enabled {
             struct_ser.serialize_field("isEnabled", &self.is_enabled)?;
@@ -1062,6 +1065,9 @@ impl serde::Serialize for DexParameters {
         if self.max_hops != 0 {
             struct_ser.serialize_field("maxHops", &self.max_hops)?;
         }
+        if self.max_positions_per_pair != 0 {
+            struct_ser.serialize_field("maxPositionsPerPair", &self.max_positions_per_pair)?;
+        }
         struct_ser.end()
     }
 }
@@ -1078,13 +1084,16 @@ impl<'de> serde::Deserialize<'de> for DexParameters {
             "fixedCandidates",
             "max_hops",
             "maxHops",
+            "max_positions_per_pair",
+            "maxPositionsPerPair",
         ];
 
         #[allow(clippy::enum_variant_names)]
         enum GeneratedField {
             IsEnabled,
             FixedCandidates,
             MaxHops,
+            MaxPositionsPerPair,
             __SkipField__,
         }
         impl<'de> serde::Deserialize<'de> for GeneratedField {
@@ -1110,6 +1119,7 @@ impl<'de> serde::Deserialize<'de> for DexParameters {
                             "isEnabled" | "is_enabled" => Ok(GeneratedField::IsEnabled),
                             "fixedCandidates" | "fixed_candidates" => Ok(GeneratedField::FixedCandidates),
                             "maxHops" | "max_hops" => Ok(GeneratedField::MaxHops),
+                            "maxPositionsPerPair" | "max_positions_per_pair" => Ok(GeneratedField::MaxPositionsPerPair),
                             _ => Ok(GeneratedField::__SkipField__),
                         }
                     }
@@ -1132,6 +1142,7 @@ impl<'de> serde::Deserialize<'de> for DexParameters {
                 let mut is_enabled__ = None;
                 let mut fixed_candidates__ = None;
                 let mut max_hops__ = None;
+                let mut max_positions_per_pair__ = None;
                 while let Some(k) = map_.next_key()? {
                     match k {
                         GeneratedField::IsEnabled => {
@@ -1154,6 +1165,14 @@ impl<'de> serde::Deserialize<'de> for DexParameters {
                                 Some(map_.next_value::<::pbjson::private::NumberDeserialize<_>>()?.0)
                             ;
                         }
+                        GeneratedField::MaxPositionsPerPair => {
+                            if max_positions_per_pair__.is_some() {
+                                return Err(serde::de::Error::duplicate_field("maxPositionsPerPair"));
+                            }
+                            max_positions_per_pair__ = 
+                                Some(map_.next_value::<::pbjson::private::NumberDeserialize<_>>()?.0)
+                            ;
+                        }
                         GeneratedField::__SkipField__ => {
                             let _ = map_.next_value::<serde::de::IgnoredAny>()?;
                         }
@@ -1163,6 +1182,7 @@ impl<'de> serde::Deserialize<'de> for DexParameters {
                     is_enabled: is_enabled__.unwrap_or_default(),
                     fixed_candidates: fixed_candidates__.unwrap_or_default(),
                     max_hops: max_hops__.unwrap_or_default(),
+                    max_positions_per_pair: max_positions_per_pair__.unwrap_or_default(),
                 })
             }
         }

proto/penumbra/penumbra/core/component/dex/v1/dex.proto

@@ -702,6 +702,10 @@ message DexParameters {
   repeated asset.v1.AssetId fixed_candidates = 2;
   // The number of hops to traverse while routing from A to B.
   uint32 max_hops = 3;
+  // The maximum number of positions per trading pair.
+  // If this number is exceeded, positions with the least
+  // inventory get evicted from the DEX.
+  uint32 max_positions_per_pair = 4;
 }
 
 message GenesisContent {