wip

Author: mgeisler

Cargo.lock

@@ -9,6 +9,7 @@ members = [
   "src/borrowing",
   "src/control-flow-basics",
   "src/error-handling",
+  "src/concurrency",
   "src/concurrency/sync-exercises",
   "src/concurrency/async-exercises",
   "src/concurrency/async-exercises/chat-async",

Cargo.toml

@@ -387,7 +387,7 @@
   - [Futures](concurrency/async/futures.md)
   - [Runtimes](concurrency/async/runtimes.md)
     - [Tokio](concurrency/async/runtimes/tokio.md)
-  - [Tasks](concurrency/async/tasks.md)
+    <!-- - [Tasks](concurrency/async/tasks.md) -->
 - [Channels and Control Flow](concurrency/async-control-flow.md)
   - [Async Channels](concurrency/async-control-flow/channels.md)
   - [Join](concurrency/async-control-flow/join.md)

src/SUMMARY.md

@@ -4,7 +4,7 @@ minutes: 8
 
 # Async Channels
 
-Several crates have support for asynchronous channels. For instance `tokio`:
+Asynchronous channels are very similar to synchronous channels:
 
 ```rust,editable,compile_fail
 {{#include channels.rs}}

src/concurrency/async-control-flow/channels.md

@@ -2,12 +2,10 @@ use tokio::sync::mpsc;
 
 async fn ping_handler(mut input: mpsc::Receiver<()>) {
     let mut count = 0;
-
     while let Some(_) = input.recv().await {
         count += 1;
         println!("Received {count} pings so far.");
     }
-
     println!("ping_handler complete");
 }
 

src/concurrency/async-control-flow/channels.rs

@@ -29,13 +29,13 @@ You are going to need the following functions from `tokio` and
 [`tokio_websockets`][2]. Spend a few minutes to familiarize yourself with the
 API.
 
-- [StreamExt::next()][3] implemented by `WebSocketStream`: for asynchronously
+- [`StreamExt::next()`][3] implemented by `WebSocketStream`: for asynchronously
   reading messages from a Websocket Stream.
-- [SinkExt::send()][4] implemented by `WebSocketStream`: for asynchronously
+- [`SinkExt::send()`][4] implemented by `WebSocketStream`: for asynchronously
   sending messages on a Websocket Stream.
-- [Lines::next_line()][5]: for asynchronously reading user messages from the
+- [`Lines::next_line()`][5]: for asynchronously reading user messages from the
   standard input.
-- [Sender::subscribe()][6]: for subscribing to a broadcast channel.
+- [`Sender::subscribe()`][6]: for subscribing to a broadcast channel.
 
 ## Two binaries
 
@@ -58,9 +58,8 @@ _src/bin/server.rs_:
 {{#include chat-async/src/bin/server.rs:setup}}
 
 {{#include chat-async/src/bin/server.rs:handle_connection}}
-
     // TODO: For a hint, see the description of the task below.
-
+    Ok(())
 {{#include chat-async/src/bin/server.rs:main}}
 ```
 
@@ -72,7 +71,7 @@ _src/bin/client.rs_:
 {{#include chat-async/src/bin/client.rs:setup}}
 
     // TODO: For a hint, see the description of the task below.
-
+    Ok(())
 }
 ```
 

src/concurrency/async-exercises/chat-app.md

@@ -44,13 +44,11 @@ impl Philosopher {
         // Keep trying until we have both forks
         // ANCHOR_END: Philosopher-eat
         let (_left_fork, _right_fork) = loop {
-            tokio::task::yield_now().await;
             // Pick up forks...
             match (self.left_fork.try_lock(), self.right_fork.try_lock()) {
-                (Ok(left_fork), Ok(right_fork)) => (left_fork, right_fork),
+                (Ok(left_fork), Ok(right_fork)) => break (left_fork, right_fork),
                 (_, _) => continue,
             };
-            break (left_fork, right_fork);
         };
 
         // ANCHOR: Philosopher-eat-body

src/concurrency/async-exercises/dining-philosophers.rs

@@ -4,9 +4,9 @@ minutes: 5
 
 # Async Traits
 
-Async methods in traits are were stabilized in the 1.75 release. This required
-support for using return-position `impl Trait` in traits, as the desugaring for
-`async fn` includes `-> impl Future<Output = ...>`.
+Async methods in traits are were stabilized in the 1.75 release (December 2023).
+This required support for using return-position `impl Trait` in traits, as the
+desugaring for `async fn` includes `-> impl Future<Output = ...>`.
 
 However, even with the native support, there are some pitfalls around
 `async fn`:

src/concurrency/async-pitfalls/async-traits.md

@@ -1,5 +1,4 @@
 use async_trait::async_trait;
-use std::time::Instant;
 use tokio::time::{sleep, Duration};
 
 #[async_trait]
@@ -18,14 +17,11 @@ impl Sleeper for FixedSleeper {
     }
 }
 
-async fn run_all_sleepers_multiple_times(
-    sleepers: Vec<Box<dyn Sleeper>>,
-    n_times: usize,
-) {
-    for _ in 0..n_times {
+async fn run_all_sleepers_multiple_times(sleepers: Vec<Box<dyn Sleeper>>) {
+    for _ in 0..5 {
         println!("Running all sleepers...");
         for sleeper in &sleepers {
-            let start = Instant::now();
+            let start = std::time::Instant::now();
             sleeper.sleep().await;
             println!("Slept for {} ms", start.elapsed().as_millis());
         }
@@ -38,5 +34,5 @@ async fn main() {
         Box::new(FixedSleeper { sleep_ms: 50 }),
         Box::new(FixedSleeper { sleep_ms: 100 }),
     ];
-    run_all_sleepers_multiple_times(sleepers, 5).await;
+    run_all_sleepers_multiple_times(sleepers).await;
 }

src/concurrency/async-pitfalls/async-traits.rs

@@ -5,9 +5,11 @@ minutes: 20
 # `Pin`
 
 Async blocks and functions return types implementing the `Future` trait. The
-type returned is the result of a compiler transformation which turns local
+type returned is the result of a [compiler transformation] which turns local
 variables into data stored inside the future.
 
+[compiler transformation]: https://tokio.rs/tokio/tutorial/async
+
 Some of those variables can hold pointers to other local variables. Because of
 that, the future should never be moved to a different memory location, as it
 would invalidate those pointers.