Refactor WS handling code (#397)

* refactor: simplify handle_text message

* refactor: rename 'TransportMessage' to 'Instruction'

* nit: update docstring on tick method

* refactor: rename dispatch to service

* nit: rename WsServer.requests to WsServer.instructions for consistency

* refactor: simplify handle_text, remove unwrap

* nit: fix misspelled comment

ethers-providers/src/pubsub.rs

@@ -48,7 +48,7 @@ where
     ///
     /// ### Note
     /// Most providers treat `SubscriptionStream` IDs as global singletons.
-    /// Instanitating this directly with a known ID will likely cause any
+    /// Instantiating this directly with a known ID will likely cause any
     /// existing streams with that ID to end. To avoid this, start a new stream
     /// using [`Provider::subscribe`] instead of `SubscriptionStream::new`.
     pub fn new(id: U256, provider: &'a Provider<P>) -> Result<Self, P::Error> {

ethers-providers/src/transports/ws.rs

@@ -30,6 +30,30 @@ use tokio_tungstenite::{
 };
 use tracing::{error, warn};
 
+type Pending = oneshot::Sender<Result<serde_json::Value, JsonRpcError>>;
+type Subscription = mpsc::UnboundedSender<serde_json::Value>;
+
+/// Instructions for the `WsServer`.
+enum Instruction {
+    /// JSON-RPC request
+    Request {
+        id: u64,
+        request: String,
+        sender: Pending,
+    },
+    /// Create a new subscription
+    Subscribe { id: U256, sink: Subscription },
+    /// Cancel an existing subscription
+    Unsubscribe { id: U256 },
+}
+
+#[derive(Debug, serde::Deserialize)]
+#[serde(untagged)]
+enum Incoming {
+    Notification(Notification<serde_json::Value>),
+    Response(Response<serde_json::Value>),
+}
+
 /// A JSON-RPC Client over Websockets.
 ///
 /// ```no_run
@@ -43,25 +67,7 @@ use tracing::{error, warn};
 #[derive(Clone)]
 pub struct Ws {
     id: Arc<AtomicU64>,
-    requests: mpsc::UnboundedSender<TransportMessage>,
-}
-
-type Pending = oneshot::Sender<Result<serde_json::Value, JsonRpcError>>;
-type Subscription = mpsc::UnboundedSender<serde_json::Value>;
-
-enum TransportMessage {
-    Request {
-        id: u64,
-        request: String,
-        sender: Pending,
-    },
-    Subscribe {
-        id: U256,
-        sink: Subscription,
-    },
-    Unsubscribe {
-        id: U256,
-    },
+    instructions: mpsc::UnboundedSender<Instruction>,
 }
 
 impl Debug for Ws {
@@ -90,13 +96,13 @@ impl Ws {
 
         Self {
             id: Arc::new(AtomicU64::new(0)),
-            requests: sink,
+            instructions: sink,
         }
     }
 
     /// Returns true if the WS connection is active, false otherwise
     pub fn ready(&self) -> bool {
-        !self.requests.is_closed()
+        !self.instructions.is_closed()
     }
 
     /// Initializes a new WebSocket Client
@@ -107,8 +113,10 @@ impl Ws {
         Ok(Self::new(ws))
     }
 
-    fn send(&self, msg: TransportMessage) -> Result<(), ClientError> {
-        self.requests.unbounded_send(msg).map_err(to_client_error)
+    fn send(&self, msg: Instruction) -> Result<(), ClientError> {
+        self.instructions
+            .unbounded_send(msg)
+            .map_err(to_client_error)
     }
 }
 
@@ -125,14 +133,14 @@ impl JsonRpcClient for Ws {
 
         // send the message
         let (sender, receiver) = oneshot::channel();
-        let payload = TransportMessage::Request {
+        let payload = Instruction::Request {
             id: next_id,
             request: serde_json::to_string(&Request::new(next_id, method, params))?,
             sender,
         };
 
         // send the data
-        self.send(payload).map_err(to_client_error)?;
+        self.send(payload)?;
 
         // wait for the response
         let res = receiver.await?;
@@ -150,7 +158,7 @@ impl PubsubClient for Ws {
 
     fn subscribe<T: Into<U256>>(&self, id: T) -> Result<Self::NotificationStream, ClientError> {
         let (sink, stream) = mpsc::unbounded();
-        self.send(TransportMessage::Subscribe {
+        self.send(Instruction::Subscribe {
             id: id.into(),
             sink,
         })?;
@@ -158,13 +166,13 @@ impl PubsubClient for Ws {
     }
 
     fn unsubscribe<T: Into<U256>>(&self, id: T) -> Result<(), ClientError> {
-        self.send(TransportMessage::Unsubscribe { id: id.into() })
+        self.send(Instruction::Unsubscribe { id: id.into() })
     }
 }
 
 struct WsServer<S> {
     ws: Fuse<S>,
-    requests: Fuse<mpsc::UnboundedReceiver<TransportMessage>>,
+    instructions: Fuse<mpsc::UnboundedReceiver<Instruction>>,
 
     pending: BTreeMap<u64, Pending>,
     subscriptions: BTreeMap<U256, Subscription>,
@@ -179,12 +187,12 @@ where
         + Unpin,
 {
     /// Instantiates the Websocket Server
-    fn new(ws: S, requests: mpsc::UnboundedReceiver<TransportMessage>) -> Self {
+    fn new(ws: S, requests: mpsc::UnboundedReceiver<Instruction>) -> Self {
         Self {
             // Fuse the 2 steams together, so that we can `select` them in the
             // Stream implementation
             ws: ws.fuse(),
-            requests: requests.fuse(),
+            instructions: requests.fuse(),
             pending: BTreeMap::default(),
             subscriptions: BTreeMap::default(),
         }
@@ -197,13 +205,13 @@ where
     {
         let f = async move {
             loop {
-                match self.process().await {
+                match self.tick().await {
                     Err(ClientError::UnexpectedClose) => {
                         tracing::error!("{}", ClientError::UnexpectedClose);
                         break;
                     }
-                    Err(_) => {
-                        panic!("WS Server panic");
+                    Err(e) => {
+                        panic!("WS Server panic: {}", e);
                     }
                     _ => {}
                 }
@@ -213,63 +221,84 @@ where
         tokio::spawn(f);
     }
 
-    /// Processes 1 item selected from the incoming `requests` or `ws`
-    #[allow(clippy::single_match)]
-    async fn process(&mut self) -> Result<(), ClientError> {
-        futures_util::select! {
-            // Handle requests
-            msg = self.requests.select_next_some() => {
-                self.handle_request(msg).await?;
-            },
-            // Handle ws messages
-            msg = self.ws.next() => match msg {
-                Some(Ok(msg)) => self.handle_ws(msg).await?,
-                // TODO: Log the error?
-                Some(Err(_)) => {},
-                None => {
-                    return Err(ClientError::UnexpectedClose);
-                },
-            }
-        };
+    // dispatch an RPC request
+    async fn service_request(
+        &mut self,
+        id: u64,
+        request: String,
+        sender: Pending,
+    ) -> Result<(), ClientError> {
+        if self.pending.insert(id, sender).is_some() {
+            warn!("Replacing a pending request with id {:?}", id);
+        }
 
+        if let Err(e) = self.ws.send(Message::Text(request)).await {
+            error!("WS connection error: {:?}", e);
+            self.pending.remove(&id);
+        }
         Ok(())
     }
 
-    async fn handle_request(&mut self, msg: TransportMessage) -> Result<(), ClientError> {
-        match msg {
-            TransportMessage::Request {
+    /// Dispatch a subscription request
+    async fn service_subscribe(&mut self, id: U256, sink: Subscription) -> Result<(), ClientError> {
+        if self.subscriptions.insert(id, sink).is_some() {
+            warn!("Replacing already-registered subscription with id {:?}", id);
+        }
+        Ok(())
+    }
+
+    /// Dispatch a unsubscribe request
+    async fn service_unsubscribe(&mut self, id: U256) -> Result<(), ClientError> {
+        if self.subscriptions.remove(&id).is_none() {
+            warn!(
+                "Unsubscribing from non-existent subscription with id {:?}",
+                id
+            );
+        }
+        Ok(())
+    }
+
+    /// Dispatch an outgoing message
+    async fn service(&mut self, instruction: Instruction) -> Result<(), ClientError> {
+        match instruction {
+            Instruction::Request {
                 id,
                 request,
                 sender,
-            } => {
-                if self.pending.insert(id, sender).is_some() {
-                    warn!("Replacing a pending request with id {:?}", id);
-                }
-
-                if let Err(e) = self.ws.send(Message::Text(request)).await {
-                    error!("WS connection error: {:?}", e);
-                    self.pending.remove(&id);
-                }
-            }
-            TransportMessage::Subscribe { id, sink } => {
-                if self.subscriptions.insert(id, sink).is_some() {
-                    warn!("Replacing already-registered subscription with id {:?}", id);
-                }
-            }
-            TransportMessage::Unsubscribe { id } => {
-                if self.subscriptions.remove(&id).is_none() {
-                    warn!(
-                        "Unsubscribing from non-existent subscription with id {:?}",
-                        id
-                    );
-                }
-            }
-        };
+            } => self.service_request(id, request, sender).await,
+            Instruction::Subscribe { id, sink } => self.service_subscribe(id, sink).await,
+            Instruction::Unsubscribe { id } => self.service_unsubscribe(id).await,
+        }
+    }
 
+    async fn handle_ping(&mut self, inner: Vec<u8>) -> Result<(), ClientError> {
+        self.ws.send(Message::Pong(inner)).await?;
         Ok(())
     }
 
-    async fn handle_ws(&mut self, resp: Message) -> Result<(), ClientError> {
+    async fn handle_text(&mut self, inner: String) -> Result<(), ClientError> {
+        match serde_json::from_str::<Incoming>(&inner) {
+            Err(_) => {}
+            Ok(Incoming::Response(resp)) => {
+                if let Some(request) = self.pending.remove(&resp.id) {
+                    request
+                        .send(resp.data.into_result())
+                        .map_err(to_client_error)?;
+                }
+            }
+            Ok(Incoming::Notification(notification)) => {
+                let id = notification.params.subscription;
+                if let Some(stream) = self.subscriptions.get(&id) {
+                    stream
+                        .unbounded_send(notification.params.result)
+                        .map_err(to_client_error)?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    async fn handle(&mut self, resp: Message) -> Result<(), ClientError> {
         match resp {
             Message::Text(inner) => self.handle_text(inner).await,
             Message::Ping(inner) => self.handle_ping(inner).await,
@@ -280,28 +309,25 @@ where
         }
     }
 
-    async fn handle_ping(&mut self, inner: Vec<u8>) -> Result<(), ClientError> {
-        self.ws.send(Message::Pong(inner)).await?;
-        Ok(())
-    }
+    /// Processes 1 instruction or 1 incoming websocket message
+    #[allow(clippy::single_match)]
+    async fn tick(&mut self) -> Result<(), ClientError> {
+        futures_util::select! {
+            // Handle requests
+            instruction = self.instructions.select_next_some() => {
+                self.service(instruction).await?;
+            },
+            // Handle ws messages
+            resp = self.ws.next() => match resp {
+                Some(Ok(resp)) => self.handle(resp).await?,
+                // TODO: Log the error?
+                Some(Err(_)) => {},
+                None => {
+                    return Err(ClientError::UnexpectedClose);
+                },
+            }
+        };
 
-    async fn handle_text(&mut self, inner: String) -> Result<(), ClientError> {
-        if let Ok(resp) = serde_json::from_str::<Response<serde_json::Value>>(&inner) {
-            if let Some(request) = self.pending.remove(&resp.id) {
-                request
-                    .send(resp.data.into_result())
-                    .map_err(to_client_error)?;
-            }
-        } else if let Ok(notification) =
-            serde_json::from_str::<Notification<serde_json::Value>>(&inner)
-        {
-            let id = notification.params.subscription;
-            if let Some(stream) = self.subscriptions.get(&id) {
-                stream
-                    .unbounded_send(notification.params.result)
-                    .map_err(to_client_error)?;
-            }
-        }
         Ok(())
     }
 }