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On worker stop #1195

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On worker stop #1195

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21 changes: 21 additions & 0 deletions server/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ pub struct Builder {
pub(crate) enable_signal: bool,
pub(crate) shutdown_timeout: Duration,
pub(crate) on_worker_start: Box<dyn Fn() -> Pin<Box<dyn Future<Output = ()> + Send>> + Send + Sync>,
pub(crate) on_worker_stop: Box<dyn Fn() -> Pin<Box<dyn Future<Output = ()> + Send>> + Send + Sync>,
backlog: u32,
}

Expand All @@ -40,6 +41,7 @@ impl Builder {
enable_signal: true,
shutdown_timeout: Duration::from_secs(30),
on_worker_start: Box::new(|| Box::pin(async {})),
on_worker_stop: Box::new(|| Box::pin(async {})),
backlog: 2048,
}
}
Expand Down Expand Up @@ -131,6 +133,25 @@ impl Builder {
self
}

#[doc(hidden)]
/// Async callback called when worker thread is being shut down.
///
/// *. This API is subject to change with no stable guarantee.
pub fn on_worker_stop<F, Fut>(mut self, on_stop: F) -> Self
where
F: Fn() -> Fut + Send + Sync + 'static,
Fut: Future + Send + 'static,
{
self.on_worker_stop = Box::new(move || {
let fut = on_stop();
Box::pin(async {
fut.await;
})
});

self
}

pub fn listen<N, L, F, St>(mut self, name: N, listener: L, service: F) -> Self
where
N: AsRef<str>,
Expand Down
7 changes: 7 additions & 0 deletions server/src/server/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@ impl Server {
factories,
shutdown_timeout,
on_worker_start,
on_worker_stop,
..
} = builder;

Expand All @@ -60,6 +61,7 @@ impl Server {
let is_graceful_shutdown = Arc::new(AtomicBool::new(false));

let on_start_fut = on_worker_start();
let on_stop_fut = on_worker_stop();
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the closure executes eagerly on worker start meaning

|| {
// happens when worker start.
async {
    // happens when worker stop.
}
}

This can be a potential footgun.

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Yup it shot me as well. Should we make this more similar to tokio's on_thread_start/on_thread_stop callbacks that just fake a non-async function?

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My opinion is we make it accepting a future rather than a closure. Reason being worker itself runs in an async context already so there is no need to do async { closure().await } and we can just do async { future.await }.
on_worker_start and tokio's case are different because these APIs have access to non async context (or partially so )

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Unfortunately I can't think of how that would work since the future would need to be awaited multiple times, once per worker task thread and that's not a power that future's have. I think that's why you used a generator pattern where the callback vends a new future each time and why Tokio doesn't have this problem since a normal Fn can be invoked multiple times.

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If you don't mind waiting on this PR for a bit we can switch to async closure when Rust 1.85 release later this month. xitca as a whole would switch to Rust 1.85 and edition 2024 at the same time. After which we can use on_worker_stop(async || {}) so there is no accidental eager execution on the closure.


let fut = async {
on_start_fut.await;
Expand All @@ -78,6 +80,8 @@ impl Server {

worker::wait_for_stop(handles, services, shutdown_timeout, &is_graceful_shutdown).await;

on_stop_fut.await;

Ok::<_, io::Error>(())
};

Expand All @@ -96,6 +100,7 @@ impl Server {
factories,
shutdown_timeout,
on_worker_start,
on_worker_stop,
..
} = builder;

Expand Down Expand Up @@ -153,6 +158,8 @@ impl Server {
}

worker::wait_for_stop(handles, services, shutdown_timeout, &is_graceful_shutdown).await;

on_worker_stop().await;
};

#[cfg(not(feature = "io-uring"))]
Expand Down
10 changes: 10 additions & 0 deletions web/src/server.rs
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Expand Up @@ -166,6 +166,16 @@ where
self
}

#[doc(hidden)]
pub fn on_worker_stop<FS, Fut>(mut self, on_stop: FS) -> Self
where
FS: Fn() -> Fut + Send + Sync + 'static,
Fut: Future + Send + 'static,
{
self.builder = self.builder.on_worker_stop(on_stop);
self
}

#[cfg(not(target_family = "wasm"))]
pub fn bind<A, ResB, BE>(mut self, addr: A) -> std::io::Result<Self>
where
Expand Down