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 BLOCKINGMAXTHREADS environment variable with value between 1 and 10000.
Read the contents of a file:
```rust use blocking::unblock; use std::fs;
let contents = unblock(|| fs::readtostring("file.txt")).await?; println!("{}", contents); ```
Read a file and pipe its contents to stdout:
```rust 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:
```rust use blocking::Unblock; use futures_lite::prelude::*; use std::fs;
let mut dir = Unblock::new(fs::readdir(".")?); while let Some(item) = dir.next().await { println!("{}", item?.filename().tostringlossy()); } ```
Spawn a process:
```rust use blocking::unblock; use std::process::Command;
let out = unblock(|| Command::new("dir").output()).await?; ```
Licensed under either of
at your option.
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.