cancel-safe-futures
Alternative futures adapters that are more cancel-safe.
What is this crate?
The futures library contains many adapters that make writing asynchronous Rust code more pleasant. However, some of those combinators make it hard to write code that can withstand cancellation in the case of timeouts, select! branches or similar.
For a more detailed explanation, see the documentation for [SinkExt::reserve].
This crate contains alternative adapters that are designed for use in scenarios where cancellation is expected.
Example
Attempt to send an item in a loop with a timeout:
use cancel_safe_futures::prelude::*;
use std::time::Duration;
let mut my_sink = /* ... */;
// This item is stored here and will be set to None once the loop exits successfully.
let mut item = Some("hello".to_owned());
let do_flush = false;
while item.is_some() {
match tokio::time::timeout(Duration::from_secs(10), my_sink.reserve()).await {
Ok(Ok(permit)) => {
let item = item.take().unwrap();
if !do_flush {
// permit.feed() feeds the item into the sink without flushing
// the sink afterwards. This is a synchronous method.
permit.feed(item)?;
} else {
// Alternatively, permit.send() writes the item into the sink
// synchronously, then returns a future which can be awaited to
// flush the sink.
permit.send(item)?.await?;
}
}
Ok(Err(error)) => return Err(error),
Err(timeout_error) => continue,
}
}
Optional features
The std and alloc features are defined and enabled by default, but not currently used. No-std users must turn off default features while importing this crate.
License
This project is available under the terms of either the Apache 2.0 license or the MIT license.
Portions derived from futures-rs, and used under the Apache 2.0 and MIT licenses.
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