30 releases (12 stable)
1.6.1 | May 26, 2024 |
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1.5.1 | Nov 13, 2023 |
1.3.1 | Apr 7, 2023 |
1.3.0 | Nov 26, 2022 |
0.1.0 | Jun 15, 2019 |
#8 in Asynchronous
2,329,965 downloads per month
Used in 4,184 crates
(67 directly)
43KB
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blocking
A thread pool for isolating blocking I/O in async programs.
Sometimes there's no way to avoid blocking I/O. Consider files or stdin, which have weak async support on modern operating systems. While IOCP, AIO, and io_uring are possible solutions, they're not always available or ideal.
Since blocking is not allowed inside futures, we must move blocking I/O onto a special thread pool provided by this crate. The pool dynamically spawns and stops threads depending on the current number of running I/O jobs.
Note that there is a limit on the number of active threads. Once that limit is hit, a running job has to finish before others get a chance to run. When a thread is idle, it waits for the next job or shuts down after a certain timeout.
The default number of threads (set to 500) can be altered by setting BLOCKING_MAX_THREADS environment variable with value between 1 and 10000.
Examples
Read the contents of a file:
use blocking::unblock;
use std::fs;
let contents = unblock(|| fs::read_to_string("file.txt")).await?;
println!("{}", contents);
Read a file and pipe its contents to stdout:
use blocking::{unblock, Unblock};
use futures_lite::io;
use std::fs::File;
let input = unblock(|| File::open("file.txt")).await?;
let input = Unblock::new(input);
let mut output = Unblock::new(std::io::stdout());
io::copy(input, &mut output).await?;
Iterate over the contents of a directory:
use blocking::Unblock;
use futures_lite::prelude::*;
use std::fs;
let mut dir = Unblock::new(fs::read_dir(".")?);
while let Some(item) = dir.next().await {
println!("{}", item?.file_name().to_string_lossy());
}
Spawn a process:
use blocking::unblock;
use std::process::Command;
let out = unblock(|| Command::new("dir").output()).await?;
License
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
Dependencies
~1MB
~14K SLoC