refactor(relay): move stream-handling away from {In,Out}boundUpgrade

Fixes: #4075.

Pull-Request: #4275.

Cargo.toml

@@ -19,6 +19,7 @@ members = [
     "interop-tests",
     "misc/allow-block-list",
     "misc/connection-limits",
+    "misc/futures-bounded",
     "misc/keygen",
     "misc/memory-connection-limits",
     "misc/metrics",
@@ -69,6 +70,7 @@ resolver = "2"
 rust-version = "1.65.0"
 
 [workspace.dependencies]
+futures-bounded = { version = "0.1.0", path = "misc/futures-bounded" }
 libp2p = { version = "0.52.3", path = "libp2p" }
 libp2p-allow-block-list = { version = "0.2.0", path = "misc/allow-block-list" }
 libp2p-autonat = { version = "0.11.0", path = "protocols/autonat" }

misc/futures-bounded/CHANGELOG.md

@@ -0,0 +1,3 @@
+## 0.1.0 - unreleased
+
+Initial release.

misc/futures-bounded/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "futures-bounded"
+version = "0.1.0"
+edition = "2021"
+rust-version.workspace = true
+license = "MIT"
+repository = "https://github.com/libp2p/rust-libp2p"
+keywords = ["futures", "async", "backpressure"]
+categories = ["data-structures", "asynchronous"]
+description = "Utilities for bounding futures in size and time."
+publish = false # TEMP FIX until https://github.com/obi1kenobi/cargo-semver-checks-action/issues/53 is fixed.
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+futures-util = { version = "0.3.28" }
+futures-timer = "3.0.2"
+
+[dev-dependencies]
+tokio = { version = "1.29.1", features = ["macros", "rt"] }

misc/futures-bounded/src/lib.rs

@@ -0,0 +1,28 @@
+mod map;
+mod set;
+
+pub use map::{FuturesMap, PushError};
+pub use set::FuturesSet;
+use std::fmt;
+use std::fmt::Formatter;
+use std::time::Duration;
+
+/// A future failed to complete within the given timeout.
+#[derive(Debug)]
+pub struct Timeout {
+    limit: Duration,
+}
+
+impl Timeout {
+    fn new(duration: Duration) -> Self {
+        Self { limit: duration }
+    }
+}
+
+impl fmt::Display for Timeout {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        write!(f, "future failed to complete within {:?}", self.limit)
+    }
+}
+
+impl std::error::Error for Timeout {}

misc/futures-bounded/src/map.rs

@@ -0,0 +1,268 @@
+use std::future::Future;
+use std::hash::Hash;
+use std::mem;
+use std::pin::Pin;
+use std::task::{Context, Poll, Waker};
+use std::time::Duration;
+
+use futures_timer::Delay;
+use futures_util::future::BoxFuture;
+use futures_util::stream::FuturesUnordered;
+use futures_util::{FutureExt, StreamExt};
+
+use crate::Timeout;
+
+/// Represents a map of [`Future`]s.
+///
+/// Each future must finish within the specified time and the map never outgrows its capacity.
+pub struct FuturesMap<ID, O> {
+    timeout: Duration,
+    capacity: usize,
+    inner: FuturesUnordered<TaggedFuture<ID, TimeoutFuture<BoxFuture<'static, O>>>>,
+    empty_waker: Option<Waker>,
+    full_waker: Option<Waker>,
+}
+
+/// Error of a future pushing
+#[derive(PartialEq, Debug)]
+pub enum PushError<F> {
+    /// The length of the set is equal to the capacity
+    BeyondCapacity(F),
+    /// The set already contains the given future's ID
+    ReplacedFuture(F),
+}
+
+impl<ID, O> FuturesMap<ID, O> {
+    pub fn new(timeout: Duration, capacity: usize) -> Self {
+        Self {
+            timeout,
+            capacity,
+            inner: Default::default(),
+            empty_waker: None,
+            full_waker: None,
+        }
+    }
+}
+
+impl<ID, O> FuturesMap<ID, O>
+where
+    ID: Clone + Hash + Eq + Send + Unpin + 'static,
+{
+    /// Push a future into the map.
+    ///
+    /// This method inserts the given future with defined `future_id` to the set.
+    /// If the length of the map is equal to the capacity, this method returns [PushError::BeyondCapacity],
+    /// that contains the passed future. In that case, the future is not inserted to the map.
+    /// If a future with the given `future_id` already exists, then the old future will be replaced by a new one.
+    /// In that case, the returned error [PushError::ReplacedFuture] contains the old future.
+    pub fn try_push<F>(&mut self, future_id: ID, future: F) -> Result<(), PushError<BoxFuture<O>>>
+    where
+        F: Future<Output = O> + Send + 'static,
+    {
+        if self.inner.len() >= self.capacity {
+            return Err(PushError::BeyondCapacity(future.boxed()));
+        }
+
+        if let Some(waker) = self.empty_waker.take() {
+            waker.wake();
+        }
+
+        match self.inner.iter_mut().find(|tagged| tagged.tag == future_id) {
+            None => {
+                self.inner.push(TaggedFuture {
+                    tag: future_id,
+                    inner: TimeoutFuture {
+                        inner: future.boxed(),
+                        timeout: Delay::new(self.timeout),
+                    },
+                });
+
+                Ok(())
+            }
+            Some(existing) => {
+                let old_future = mem::replace(
+                    &mut existing.inner,
+                    TimeoutFuture {
+                        inner: future.boxed(),
+                        timeout: Delay::new(self.timeout),
+                    },
+                );
+
+                Err(PushError::ReplacedFuture(old_future.inner))
+            }
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    #[allow(unknown_lints, clippy::needless_pass_by_ref_mut)] // &mut Context is idiomatic.
+    pub fn poll_ready_unpin(&mut self, cx: &mut Context<'_>) -> Poll<()> {
+        if self.inner.len() < self.capacity {
+            return Poll::Ready(());
+        }
+
+        self.full_waker = Some(cx.waker().clone());
+
+        Poll::Pending
+    }
+
+    pub fn poll_unpin(&mut self, cx: &mut Context<'_>) -> Poll<(ID, Result<O, Timeout>)> {
+        let maybe_result = futures_util::ready!(self.inner.poll_next_unpin(cx));
+
+        match maybe_result {
+            None => {
+                self.empty_waker = Some(cx.waker().clone());
+                Poll::Pending
+            }
+            Some((id, Ok(output))) => Poll::Ready((id, Ok(output))),
+            Some((id, Err(_timeout))) => Poll::Ready((id, Err(Timeout::new(self.timeout)))),
+        }
+    }
+}
+
+struct TimeoutFuture<F> {
+    inner: F,
+    timeout: Delay,
+}
+
+impl<F> Future for TimeoutFuture<F>
+where
+    F: Future + Unpin,
+{
+    type Output = Result<F::Output, ()>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        if self.timeout.poll_unpin(cx).is_ready() {
+            return Poll::Ready(Err(()));
+        }
+
+        self.inner.poll_unpin(cx).map(Ok)
+    }
+}
+
+struct TaggedFuture<T, F> {
+    tag: T,
+    inner: F,
+}
+
+impl<T, F> Future for TaggedFuture<T, F>
+where
+    T: Clone + Unpin,
+    F: Future + Unpin,
+{
+    type Output = (T, F::Output);
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let output = futures_util::ready!(self.inner.poll_unpin(cx));
+
+        Poll::Ready((self.tag.clone(), output))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::future::{pending, poll_fn, ready};
+    use std::pin::Pin;
+    use std::time::Instant;
+
+    use super::*;
+
+    #[test]
+    fn cannot_push_more_than_capacity_tasks() {
+        let mut futures = FuturesMap::new(Duration::from_secs(10), 1);
+
+        assert!(futures.try_push("ID_1", ready(())).is_ok());
+        matches!(
+            futures.try_push("ID_2", ready(())),
+            Err(PushError::BeyondCapacity(_))
+        );
+    }
+
+    #[test]
+    fn cannot_push_the_same_id_few_times() {
+        let mut futures = FuturesMap::new(Duration::from_secs(10), 5);
+
+        assert!(futures.try_push("ID", ready(())).is_ok());
+        matches!(
+            futures.try_push("ID", ready(())),
+            Err(PushError::ReplacedFuture(_))
+        );
+    }
+
+    #[tokio::test]
+    async fn futures_timeout() {
+        let mut futures = FuturesMap::new(Duration::from_millis(100), 1);
+
+        let _ = futures.try_push("ID", pending::<()>());
+        Delay::new(Duration::from_millis(150)).await;
+        let (_, result) = poll_fn(|cx| futures.poll_unpin(cx)).await;
+
+        assert!(result.is_err())
+    }
+
+    // Each future causes a delay, `Task` only has a capacity of 1, meaning they must be processed in sequence.
+    // We stop after NUM_FUTURES tasks, meaning the overall execution must at least take DELAY * NUM_FUTURES.
+    #[tokio::test]
+    async fn backpressure() {
+        const DELAY: Duration = Duration::from_millis(100);
+        const NUM_FUTURES: u32 = 10;
+
+        let start = Instant::now();
+        Task::new(DELAY, NUM_FUTURES, 1).await;
+        let duration = start.elapsed();
+
+        assert!(duration >= DELAY * NUM_FUTURES);
+    }
+
+    struct Task {
+        future: Duration,
+        num_futures: usize,
+        num_processed: usize,
+        inner: FuturesMap<u8, ()>,
+    }
+
+    impl Task {
+        fn new(future: Duration, num_futures: u32, capacity: usize) -> Self {
+            Self {
+                future,
+                num_futures: num_futures as usize,
+                num_processed: 0,
+                inner: FuturesMap::new(Duration::from_secs(60), capacity),
+            }
+        }
+    }
+
+    impl Future for Task {
+        type Output = ();
+
+        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+            let this = self.get_mut();
+
+            while this.num_processed < this.num_futures {
+                if let Poll::Ready((_, result)) = this.inner.poll_unpin(cx) {
+                    if result.is_err() {
+                        panic!("Timeout is great than future delay")
+                    }
+
+                    this.num_processed += 1;
+                    continue;
+                }
+
+                if let Poll::Ready(()) = this.inner.poll_ready_unpin(cx) {
+                    // We push the constant future's ID to prove that user can use the same ID
+                    // if the future was finished
+                    let maybe_future = this.inner.try_push(1u8, Delay::new(this.future));
+                    assert!(maybe_future.is_ok(), "we polled for readiness");
+
+                    continue;
+                }
+
+                return Poll::Pending;
+            }
+
+            Poll::Ready(())
+        }
+    }
+}