feat(batcher): Notify the user that proof has been replaced

Author: maximopalopoli

crates/batcher/src/lib.rs

@@ -1496,13 +1496,25 @@ impl Batcher {
         // Close old sink in old entry and replace it with the new one
         {
             if let Some(messaging_sink) = replacement_entry.messaging_sink {
-                let mut old_sink = messaging_sink.write().await;
-                if let Err(e) = old_sink.close().await {
-                    // we dont want to exit here, just log the error
-                    warn!("Error closing sink: {e:?}");
-                } else {
-                    info!("Old websocket sink closed");
-                }
+                tokio::spawn(async move {
+                    // Before closing the old sink, send a message to the client notifying that their proof
+                    // has been replaced
+                    send_message(
+                        messaging_sink.clone(),
+                        SubmitProofResponseMessage::ProofReplaced,
+                    ).await;
+
+                    // Note: This shuts down the sink, but does not wait for it to close, so the other side
+                    // might not receive the message. However, we don't want to wait here since it would
+                    // block the batcher.
+                    let mut old_sink = messaging_sink.write().await;
+                    if let Err(e) = old_sink.close().await {
+                        // we dont want to exit here, just log the error
+                        warn!("Error closing sink: {e:?}");
+                    } else {
+                        info!("Old websocket sink closed");
+                    }
+                });
             } else {
                 warn!(
                     "Old websocket sink was empty. This should only happen in testing environments"

crates/sdk/src/common/errors.rs

@@ -99,6 +99,7 @@ pub enum SubmitError {
     BatchQueueLimitExceededError,
     GenericError(String),
     UserFundsUnlocked,
+    ProofReplaced,
 }
 
 impl From<tokio_tungstenite::tungstenite::Error> for SubmitError {
@@ -213,9 +214,9 @@ impl fmt::Display for SubmitError {
                 write!(f, "Batcher responded with invalid batch inclusion data. Can't verify your proof was correctly included in the batch.")
             }
             SubmitError::BatchQueueLimitExceededError => {
-                write!(f, "Error while adding entry to batch, queue limit exeeded.")
+                write!(f, "Error while adding entry to batch, queue limit exceeded.")
             }
-
+            SubmitError::ProofReplaced => write!(f, "Proof has been replaced by a higher fee for the same proof"),
             SubmitError::GetNonceError(e) => write!(f, "Error while getting nonce {}", e),
             SubmitError::UserFundsUnlocked => write!(
                 f,

crates/sdk/src/common/types.rs

@@ -454,6 +454,7 @@ pub enum SubmitProofResponseMessage {
     UnderpricedProof,
     ServerBusy,
     UserFundsUnlocked,
+    ProofReplaced,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]

crates/sdk/src/communication/messaging.rs

@@ -279,6 +279,10 @@ async fn handle_batcher_response(msg: Message) -> Result<BatchInclusionData, Sub
             error!("User funds have been unlocked and proofs removed from queue. Funds have not been spent.");
             Err(SubmitError::UserFundsUnlocked)
         }
+        Ok(SubmitProofResponseMessage::ProofReplaced) => {
+            error!("Proof has been replaced by a higher fee for the same proof. Funds have not been spent.");
+            Err(SubmitError::ProofReplaced)
+        }
         Err(e) => {
             error!(
                 "Error while deserializing batch inclusion data: {}. Funds have not been spent.",