From bc59f94c1bc56f810dc51f0d9d04b3cdbb177e3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jon=20H=C3=A4ggblad?= <jon.haggblad@gmail.com>
Date: Mon, 6 May 2024 11:56:30 +0200
Subject: [PATCH] Pass errors up the call stack

---
 common/client-core/src/client/mix_traffic/mod.rs  | 15 +++++++--------
 .../src/client/mix_traffic/transceiver.rs         |  6 ++++++
 common/client-core/src/error.rs                   |  8 ++++++++
 common/client-libs/gateway-client/src/error.rs    |  3 +++
 .../gateway-client/src/socket_state.rs            |  6 +++---
 5 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/common/client-core/src/client/mix_traffic/mod.rs b/common/client-core/src/client/mix_traffic/mod.rs
index 133794b225..6b52d40c01 100644
--- a/common/client-core/src/client/mix_traffic/mod.rs
+++ b/common/client-core/src/client/mix_traffic/mod.rs
@@ -85,18 +85,21 @@ impl MixTrafficController {
                 error!("Failed to send sphinx packet(s) to the gateway: {err}");
                 self.consecutive_gateway_failure_count += 1;
                 if self.consecutive_gateway_failure_count == MAX_FAILURE_COUNT {
-                    // todo: in the future this should initiate a 'graceful' shutdown or try
-                    // to reconnect?
-                    panic!("failed to send sphinx packet to the gateway {MAX_FAILURE_COUNT} times in a row - assuming the gateway is dead. Can't do anything about it yet :(")
+                    Err(ClientCoreError::GatewayMaxRetriesExceeded)
+                } else {
+                    Err(ClientCoreError::GatewayClientSendError {
+                        gateway_client_error: err.to_string(),
+                    })
                 }
             }
             Ok(_) => {
                 trace!("We *might* have managed to forward sphinx packet(s) to the gateway!");
                 self.consecutive_gateway_failure_count = 0;
+                Ok(())
             }
         };
         info!("JON: MixTrafficController: done sending sphinx packets to the gateway");
-        Ok(r)
+        r
     }
 
     pub fn start_with_shutdown(mut self, mut shutdown: nym_task::TaskClient) {
@@ -120,10 +123,6 @@ impl MixTrafficController {
                             if let Err(err) = self.on_messages(mix_packets).await {
                                 log::error!("MixTrafficController: failed to send mix packets to the gateway: {err}");
                             }
-                            // let r = tokio::time::timeout(tokio::time::Duration::from_secs(4), self.on_messages(mix_packets)).await;
-                            // if r.is_err() {
-                            //     error!("MixTrafficController: Failed to send mix packets to the gateway");
-                            // }
                             log::info!("JON: MixTrafficController: done with mix_rx recv");
                         },
                         None => {
diff --git a/common/client-core/src/client/mix_traffic/transceiver.rs b/common/client-core/src/client/mix_traffic/transceiver.rs
index b7202f031a..9bb970ed36 100644
--- a/common/client-core/src/client/mix_traffic/transceiver.rs
+++ b/common/client-core/src/client/mix_traffic/transceiver.rs
@@ -19,6 +19,12 @@ use futures::channel::{mpsc, oneshot};
 #[error(transparent)]
 pub struct ErasedGatewayError(Box<dyn std::error::Error + Send + Sync>);
 
+impl ErasedGatewayError {
+    pub fn downcast<T: std::error::Error + 'static>(&self) -> Option<&T> {
+        self.0.downcast_ref::<T>()
+    }
+}
+
 fn erase_err<E: std::error::Error + Send + Sync + 'static>(err: E) -> ErasedGatewayError {
     ErasedGatewayError(Box::new(err))
 }
diff --git a/common/client-core/src/error.rs b/common/client-core/src/error.rs
index bdfecfda5e..195e5a8c35 100644
--- a/common/client-core/src/error.rs
+++ b/common/client-core/src/error.rs
@@ -78,6 +78,9 @@ pub enum ClientCoreError {
         source: tungstenite::Error,
     },
 
+    #[error("max number of retries for gateway connection has been exceeded")]
+    GatewayMaxRetriesExceeded,
+
     #[cfg(target_arch = "wasm32")]
     #[error("failed to establish gateway connection (wasm)")]
     GatewayJsConnectionFailure,
@@ -88,6 +91,11 @@ pub enum ClientCoreError {
     #[error("timed out while trying to establish gateway connection")]
     GatewayConnectionTimeout,
 
+    #[error("failed to send sphinx packet to the gateway: {gateway_client_error}")]
+    GatewayClientSendError {
+        gateway_client_error: String,
+    },
+
     #[error("no ping measurements for the gateway ({identity}) performed")]
     NoGatewayMeasurements { identity: String },
 
diff --git a/common/client-libs/gateway-client/src/error.rs b/common/client-libs/gateway-client/src/error.rs
index e2d9aae77c..28fd5900d0 100644
--- a/common/client-libs/gateway-client/src/error.rs
+++ b/common/client-libs/gateway-client/src/error.rs
@@ -74,6 +74,9 @@ pub enum GatewayClientError {
     #[error("Timed out")]
     Timeout,
 
+    #[error("timeout sending ws message to the gateway")]
+    TimeoutOnSendingWs,
+
     #[error("Failed to send mixnet message")]
     MixnetMsgSenderFailedToSend,
 
diff --git a/common/client-libs/gateway-client/src/socket_state.rs b/common/client-libs/gateway-client/src/socket_state.rs
index 592aa392c6..29756eedf5 100644
--- a/common/client-libs/gateway-client/src/socket_state.rs
+++ b/common/client-libs/gateway-client/src/socket_state.rs
@@ -222,14 +222,14 @@ impl PartiallyDelegated {
         // Ok(r?)
         let r = tokio::time::timeout(Duration::from_secs(3), self.sink_half.send(msg)).await;
         let rr = match r {
-            Ok(rr) => rr,
+            Ok(rr) => Ok(rr?),
             Err(_) => {
                 log::error!("JON: PartiallyDelegated::send_without_response - timeout sending a message");
-                Ok(())
+                Err(GatewayClientError::TimeoutOnSendingWs)
             }
         };
         log::info!("JON: PartiallyDelegated::send_without_response - sent a message: {rr:?}");
-        Ok(rr?)
+        rr
     }
 
     pub(crate) async fn batch_send_without_response(