2 stable releases
1.0.1 | Jan 16, 2024 |
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0.1.0 |
|
#478 in Asynchronous
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38KB
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Futures-Ratelimit
Bounded versions of FuturesUnordered
/FuturesOrdered
This crate provides bounded versions of FuturesUnordered
/FuturesOrdered
.
The usual futures' FuturesUnordered
/FuturesOrdered
structs don't provide any means to limit how many
futures are polled at any given time. While you can use semaphores or any other
forms of resource locking, that won't stop the async runtime from potentially
polling (and thus, wasting CPU) too many futures at once. You can use channels, but
that feels cumbersome and means extra code and added overhead.
This crate provides types that behave just like the usual futures
-(un)ordered types,
except that you can specify a maximum number of futures that can be polled at any
given time. This allows you to create and submit tons of futures without
overwhelming the async runtime. 100% drop-in replacements for FuturesOrdered
and
FuturesUnordered
are also provided.
The logic behind this crate is rather simple: we override the underlying' poll_next()
,
and, when necessary, pop a new future from either an iterator or a queue (at your
choice). This means that we'll always be running exactly N futures (or less, if
the futures source has been exhausted).
The wrapped types have been designed such that the checks (to pop for more futures) are executed only when needed, thus making everything as efficient as it gets.
Basic example:
use futures_ratelimit::ordered::FuturesOrderedBounded;
use futures_ratelimit::common::Passthrough;
use futures::StreamExt;
async fn dummy() -> u64{
42
}
let mut fut_unordered = FuturesOrderedBounded::new(5);
for _ in 0..10 {
fut_unordered.push_back(dummy());
}
// The internal FuturesOrderedBounded will have 5 futures at most.
tokio_test::block_on(async move{
assert_eq!(fut_unordered.borrow_inner().len(), 5);
while let Some(value) = fut_unordered.next().await {
println!("{}", value);
assert!(fut_unordered.borrow_inner().len() <= 5);
}
assert_eq!(fut_unordered.borrow_inner().len(), 0);
assert!(fut_unordered.borrow_inner().is_empty());
});
Make sure to check out the docs for examples!
LICENSE
MIT
Notes
The name of this library is intentionally misleading. It was supposed to be
futures-bounded
, but that name is already being used in crates.io by someone else and
rate-limit
kinda conveys the same meaning.
Dependencies
~1–1.6MB
~33K SLoC