feat: custom lag error

Author: LeoPatOZ

src/error.rs

@@ -33,6 +33,9 @@ pub enum ScannerError {
 
     #[error("Subscription closed")]
     SubscriptionClosed,
+
+    #[error("Subscriptions Lagged too often")]
+    SubscriptionLagged,
 }
 
 impl From<RobustProviderError> for ScannerError {
@@ -42,6 +45,7 @@ impl From<RobustProviderError> for ScannerError {
             RobustProviderError::RpcError(err) => ScannerError::RpcError(err),
             RobustProviderError::BlockNotFound(block) => ScannerError::BlockNotFound(block),
             RobustProviderError::Closed => ScannerError::SubscriptionClosed,
+            RobustProviderError::SubscriptionLagged => ScannerError::SubscriptionLagged,
         }
     }
 }

src/robust_provider/error.rs

@@ -1,3 +1,4 @@
+use crate::robust_provider::subscription::MAX_LAG_COUNT;
 use std::sync::Arc;
 
 use alloy::{
@@ -17,6 +18,8 @@ pub enum Error {
     BlockNotFound(BlockId),
     #[error("Subscription closed")]
     Closed,
+    #[error("Subscription lag exceeded maximum consecutive lag count: {MAX_LAG_COUNT:?}")]
+    SubscriptionLagged,
 }
 
 impl From<RpcError<TransportErrorKind>> for Error {

src/robust_provider/subscription.rs

@@ -8,7 +8,6 @@ use alloy::{
     network::Network,
     providers::{Provider, RootProvider},
     pubsub::Subscription,
-    transports::{RpcError, TransportErrorKind},
 };
 use tokio::{sync::broadcast::error::RecvError, time::timeout};
 use tokio_stream::Stream;
@@ -124,11 +123,7 @@ impl<N: Network> RobustSubscription<N> {
 
                 if self.consecutive_lags >= MAX_LAG_COUNT {
                     warn!("Too many consecutive lags, switching provider");
-                    let error = RpcError::Transport(TransportErrorKind::Custom(
-                        "Encountered too much lag".into(),
-                    ))
-                    .into();
-                    self.switch_to_fallback(error).await?;
+                    self.switch_to_fallback(Error::SubscriptionLagged).await?;
                 }
             }
         }
@@ -324,6 +319,9 @@ mod tests {
             Error::Closed => {
                 panic!("Unexpected Closed error");
             }
+            Error::SubscriptionLagged => {
+                panic!("Unexpected SubscriptionLagged error");
+            }
         }
     }