fix: u64 overflow when updating relayer metrics (#471)

crates/relayer-utils/src/metric.rs

@@ -21,7 +21,7 @@ use webb_proposals::ResourceId;
 /// A struct for collecting metrics for particular resource.
 #[derive(Debug, Clone)]
 pub struct ResourceMetric {
-    /// Total gas spent on Resource.
+    /// Total gas spent (in gwei) on Resource.
     pub total_gas_spent: GenericCounter<AtomicF64>,
     /// Total fees earned on Resource.
     pub total_fee_earned: GenericCounter<AtomicF64>,
@@ -174,7 +174,7 @@ impl Metrics {
         let total_gas_spent_counter = register_counter!(
             format!("resource_{resource_hex}_total_gas_spent"),
             format!(
-                "The total number of gas spent on resource : {resource_hex}"
+                "The total number of gas (in gwei) spent on resource : {resource_hex}"
             )
         );
         // Total fee earned on particular resource.

crates/tx-relay/src/evm/mod.rs

@@ -2,6 +2,7 @@ use std::{sync::Arc, time::Duration};
 
 use tokio::sync::Mutex;
 use webb::evm::ethers::{
+    self,
     abi::Detokenize,
     prelude::{builders::ContractCall, Middleware},
 };
@@ -95,22 +96,26 @@ where
         finalized = true,
         tx_hash = %receipt.transaction_hash,
     );
+    // send the finalized status to the client.
+    let _ = stream
+        .send(Withdraw(WithdrawStatus::Finalized {
+            tx_hash: receipt.transaction_hash,
+        }))
+        .await;
     // gas spent by relayer on particular resource.
-    let gas_price = receipt.gas_used.unwrap_or_default();
+    let gas_used = receipt.gas_used.unwrap_or_default();
     let mut metrics = metrics.lock().await;
     let resource_metric = metrics
         .resource_metric_map
         .entry(resource_id)
         .or_insert_with(|| Metrics::register_resource_id_counters(resource_id));
-
-    resource_metric
-        .total_gas_spent
-        .inc_by(gas_price.as_u64() as f64);
-    drop(metrics);
-    let _ = stream
-        .send(Withdraw(WithdrawStatus::Finalized {
-            tx_hash: receipt.transaction_hash,
-        }))
-        .await;
+    // convert gas used to gwei.
+    let gas_used = ethers::utils::format_units(gas_used, "gwei")
+        .and_then(|gas| {
+            gas.parse::<f64>()
+                .map_err(|_| ethers::utils::ConversionError::ParseOverflow)
+        })
+        .unwrap_or_default();
+    resource_metric.total_gas_spent.inc_by(gas_used);
     Ok(())
 }