Update the release profile

Co-authored-by: xermicus <cyrill@parity.io>

Cargo.toml

@@ -78,15 +78,3 @@ features = [
 inherits = "release"
 lto = true
 codegen-units = 1
-
-# We set the `panic` behavior to `unwind` in both the `release` and `dev` profiles since our async 
-# runtime attempts to catch panics and it can only catch panics if we compile our code with unwind
-# as the panic behavior. For more information, please see the `catch_unwind` documentation where it
-# mentions that panics can only be caught if they unwind and not if they abort:
-# https://doc.rust-lang.org/std/panic/fn.catch_unwind.html#notes
-
-[profile.release]
-panic = "unwind"
-
-[profile.dev]
-panic = "unwind"

crates/node-interaction/src/blocking_executor.rs

@@ -51,35 +51,37 @@ impl BlockingExecutor {
     where
         R: Send + 'static,
     {
-        // A static of the state associated with the async runtime. This is initialized on the first
-        // access of the state.
+        // Note: The blocking executor is a singleton and therefore we store its state in a static
+        // so that it's assigned only once. Additionally, when we set the state of the executor we
+        // spawn the thread where the async runtime runs.
         static STATE: Lazy<ExecutorState> = Lazy::new(|| {
             tracing::trace!("Initializing the BlockingExecutor state");
 
-            // Creating a multiple-producer-single-consumer channel which allows all of the other
-            // threads to communicate with this one async runtime thread.
+            // All communication with the tokio runtime thread happens over mspc channels where the
+            // producers here are the threads that want to run async tasks and the consumer here is
+            // the tokio runtime thread.
             let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel::<TaskMessage>();
 
-            // We spawn a new thread which will house the async runtime and will always be listening
-            // for new tasks coming in and executing them as they come in.
             thread::spawn(move || {
-                // Creating the tokio runtime on this current thread.
                 let runtime = Builder::new_current_thread()
                     .enable_all()
                     .build()
                     .expect("Failed to create the async runtime");
 
                 runtime.block_on(async move {
-                    // Keep getting new task messages from all of the other threads.
                     while let Some(TaskMessage {
                         future: task,
                         response_tx: response_channel,
                     }) = rx.recv().await
                     {
-                        // Spawn off each job so that the receive loop is not blocked.
                         tracing::trace!("Received a new future to execute");
                         tokio::spawn(async move {
+                            // One of the things that the blocking executor does is that it allows
+                            // us to catch panics if they occur. By wrapping the given future in an
+                            // AssertUnwindSafe::catch_unwind we are able to catch all panic unwinds
+                            // in the given future and convert them into errors.
                             let task = AssertUnwindSafe(task).catch_unwind();
+
                             let result = task.await;
                             let _ = response_channel.send(result);
                         });
@@ -87,31 +89,32 @@ impl BlockingExecutor {
                 })
             });
 
-            // Creating the state of the async runtime.
             ExecutorState { tx }
         });
 
-        // Creating a one-shot channel for this task that will be used to send and receive the
-        // response of the task.
+        // We need to perform blocking synchronous communication between the current thread and the
+        // tokio runtime thread with the result of the async computation and the oneshot channels
+        // from tokio allows us to do that. The sender side of the channel will be given to the
+        // tokio runtime thread to send the result when the computation is completed and the receive
+        // side of the channel will be kept with this thread to await for the response of the async
+        // task to come back.
         let (response_tx, response_rx) =
             oneshot::channel::<Result<Box<dyn Any + Send>, Box<dyn Any + Send>>>();
 
-        // Converting the future from the shape that it is in into the shape that the runtime is
-        // expecting it to be in.
+        // The tokio runtime thread expects a Future<Output = Box<dyn Any + Send>> + Send to be
+        // sent to it to execute. However, this function has a typed Future<Output = R> + Send and
+        // therefore we need to change the type of the future to fit what the runtime thread expects
+        // in the task message. In doing this conversion, we lose some of the type information since
+        // we're converting R => dyn Any. However, we will perform down-casting on the result to
+        // convert it back into R.
         let future = Box::pin(async move { Box::new(future.await) as Box<dyn Any + Send> });
 
-        // Sending the task to the runtime,
-        let task = TaskMessage {
-            future,
-            response_tx,
-        };
-
+        let task = TaskMessage::new(future, response_tx);
         if let Err(error) = STATE.tx.send(task) {
             tracing::error!(?error, "Failed to send the task to the blocking executor");
             anyhow::bail!("Failed to send the task to the blocking executor: {error:?}")
         }
 
-        // Await for the result of the execution to come back over the channel.
         let result = match response_rx.blocking_recv() {
             Ok(result) => result,
             Err(error) => {
@@ -141,6 +144,7 @@ impl BlockingExecutor {
         }
     }
 }
+
 /// Represents the state of the async runtime. This runtime is designed to be a singleton runtime
 /// which means that in the current running program there's just a single thread that has an async
 /// runtime.
@@ -163,6 +167,18 @@ struct TaskMessage {
     response_tx: oneshot::Sender<Result<Box<dyn Any + Send>, Box<dyn Any + Send>>>,
 }
 
+impl TaskMessage {
+    pub fn new(
+        future: Pin<Box<dyn Future<Output = Box<dyn Any + Send>> + Send>>,
+        response_tx: oneshot::Sender<Result<Box<dyn Any + Send>, Box<dyn Any + Send>>>,
+    ) -> Self {
+        Self {
+            future,
+            response_tx,
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;