2 releases
0.1.1 | Apr 20, 2022 |
---|---|
0.1.0 | Apr 20, 2022 |
#8 in #polling
6KB
rust-future-wrap
A minimal crate that lets you wrap a future to track each poll and modify the outcome.
It only contains a single trait called WrapFuture
which adds a wrap
function to all types that
implement std::future::Future
. The wrap
takes a closure as an argument which will be called whenever the future is
polled. The closure receives the wrapped Pin<Future>
and is responsible for calling poll
on it with the received
waker context. The closure can return std::task::Poll<T>
of any type T
and can therefore modify the return type of
the wrapped future (similar to Future.map
).
Example
This examples shows how to track and limit the time spend on polling a future.
use std::future::Future;
use std::task::Poll;
use std::time::{Duration, Instant};
use tokio::runtime::Builder;
use tokio::time::sleep;
use future_wrap::WrapFuture;
async fn some_async_fn() {
sleep(Duration::from_secs(1)).await;
std::thread::sleep(Duration::from_millis(3));
sleep(Duration::from_secs(1)).await;
std::thread::sleep(Duration::from_millis(3));
sleep(Duration::from_secs(1)).await;
std::thread::sleep(Duration::from_millis(3));
sleep(Duration::from_secs(1)).await;
std::thread::sleep(Duration::from_millis(3));
sleep(Duration::from_secs(1)).await;
}
fn main() {
let runtime = Builder::new_current_thread()
.enable_time()
.build()
.unwrap();
runtime.block_on(async move {
let fut = some_async_fn();
let mut remaining_time = Duration::from_millis(10);
fut.wrap(|fut, cx| {
let poll_start = Instant::now();
println!("Poll start");
let res = fut.poll(cx);
println!("Poll end");
remaining_time = remaining_time.saturating_sub(poll_start.elapsed());
if remaining_time.is_zero() {
println!("Too much time spent on polls :(");
Poll::Ready(None)
} else {
res.map(|v| Some(v))
}
}).await;
});
}
Dependencies
~0.3–0.8MB
~18K SLoC