[EASY] Make gas offset configurable

src/domain/dex/mod.rs

@@ -108,6 +108,7 @@ impl Swap {
         gas_price: auction::GasPrice,
         sell_token: Option<auction::Price>,
         simulator: &infra::dex::Simulator,
+        gas_offset: eth::Gas,
     ) -> Option<solution::Solution> {
         let gas = if order.class == order::Class::Limit {
             match simulator.gas(order.owner(), &self).await {
@@ -141,7 +142,7 @@ impl Swap {
             interactions,
             gas,
         }
-        .into_solution(gas_price, sell_token)
+        .into_solution(gas_price, sell_token, gas_offset)
     }
 
     pub fn satisfies(&self, order: &domain::order::Order) -> bool {

src/domain/solution.rs

@@ -116,15 +116,13 @@ pub struct Single {
 }
 
 impl Single {
-    /// An approximation for the overhead of executing a trade in a settlement.
-    const SETTLEMENT_OVERHEAD: u64 = 106_391;
-
     /// Creates a full solution for a single order solution given gas and sell
     /// token prices.
     pub fn into_solution(
         self,
         gas_price: auction::GasPrice,
         sell_token: Option<auction::Price>,
+        gas_offset: eth::Gas,
     ) -> Option<Solution> {
         let Self {
             order,
@@ -147,7 +145,7 @@ impl Single {
             Fee::Surplus(
                 sell_token?.ether_value(eth::Ether(
                     swap.0
-                        .checked_add(Self::SETTLEMENT_OVERHEAD.into())?
+                        .checked_add(gas_offset.0)?
                         .checked_mul(gas_price.0 .0)?,
                 ))?,
             )
@@ -198,7 +196,7 @@ impl Single {
             ]),
             trades: vec![Trade::Fulfillment(Fulfillment::new(order, executed, fee)?)],
             interactions,
-            gas: Some(eth::Gas(Self::SETTLEMENT_OVERHEAD.into()) + self.gas),
+            gas: Some(gas_offset + self.gas),
         })
     }
 }

src/domain/solver/dex/mod.rs

@@ -6,6 +6,7 @@ use {
         domain::{
             auction,
             dex::{self, slippage},
+            eth,
             order::{self, Order},
             solution,
             solver::dex::fills::Fills,
@@ -38,6 +39,10 @@ pub struct Dex {
 
     /// Handles 429 Too Many Requests error with a retry mechanism
     rate_limiter: rate_limit::RateLimiter,
+
+    /// Amount of gas that gets added to each swap to tweak the cost coverage of
+    /// the solver.
+    gas_offset: eth::Gas,
 }
 
 /// The amount of time we aim the solver to finish before the final deadline is
@@ -61,6 +66,7 @@ impl Dex {
             concurrent_requests: config.concurrent_requests,
             fills: Fills::new(config.smallest_partial_fill),
             rate_limiter,
+            gas_offset: config.gas_offset,
         }
     }
 
@@ -177,7 +183,13 @@ impl Dex {
         let swap = self.try_solve(order, &dex_order, tokens, gas_price).await?;
         let sell = tokens.reference_price(&order.sell.token);
         let Some(solution) = swap
-            .into_solution(order.clone(), gas_price, sell, &self.simulator)
+            .into_solution(
+                order.clone(),
+                gas_price,
+                sell,
+                &self.simulator,
+                self.gas_offset,
+            )
             .await
         else {
             tracing::debug!("no solution for swap");

src/infra/config/dex/file.rs

@@ -58,6 +58,12 @@ struct Config {
 
     /// Settings specific to the wrapped dex API.
     dex: toml::Value,
+
+    /// Amount of gas that gets added to each swap to adjust the cost coverage
+    /// of the solver.
+    #[serde(default = "default_gas_offset")]
+    #[serde_as(as = "serialize::U256")]
+    gas_offset: eth::U256,
 }
 
 fn default_relative_slippage() -> BigDecimal {
@@ -84,6 +90,12 @@ fn default_max_back_off() -> Duration {
     Duration::from_secs(8)
 }
 
+fn default_gas_offset() -> eth::U256 {
+    // Rough estimation of the gas overhead of settling a single
+    // trade via the settlement contract.
+    106_391.into()
+}
+
 /// Loads the base solver configuration from a TOML file.
 ///
 /// # Panics
@@ -137,6 +149,7 @@ pub async fn load<T: DeserializeOwned>(path: &Path) -> (super::Config, T) {
             config.max_back_off,
         )
         .unwrap(),
+        gas_offset: eth::Gas(config.gas_offset),
     };
     (config, dex)
 }

src/infra/config/dex/mod.rs

@@ -23,4 +23,5 @@ pub struct Config {
     pub concurrent_requests: NonZeroUsize,
     pub smallest_partial_fill: eth::Ether,
     pub rate_limiting_strategy: rate_limit::Strategy,
+    pub gas_offset: eth::Gas,
 }