async-backtrace

Efficient, logical 'stack' traces of async functions.

Usage

To use, annotate your async functions with #[async_backtrace::framed], like so:

#[tokio::main]
async fn main() {
    tokio::select! {
        _ = tokio::spawn(async_backtrace::frame!(pending())) => {}
        _ = foo() => {}
    };
}

#[async_backtrace::framed]
async fn pending() {
    std::future::pending::<()>().await
}

#[async_backtrace::framed]
async fn foo() {
    bar().await;
}

#[async_backtrace::framed]
async fn bar() {
    futures::join!(fiz(), buz());
}

#[async_backtrace::framed]
async fn fiz() {
    tokio::task::yield_now().await;
}

#[async_backtrace::framed]
async fn buz() {
    println!("{}", baz().await);
}

#[async_backtrace::framed]
async fn baz() -> String {
    async_backtrace::taskdump_tree(true)
}

This example program will print out something along the lines of:

╼ taskdump::foo::{{closure}} at backtrace/examples/taskdump.rs:20:1
  └╼ taskdump::bar::{{closure}} at backtrace/examples/taskdump.rs:25:1
     ├╼ taskdump::buz::{{closure}} at backtrace/examples/taskdump.rs:35:1
     │  └╼ taskdump::baz::{{closure}} at backtrace/examples/taskdump.rs:40:1
     └╼ taskdump::fiz::{{closure}} at backtrace/examples/taskdump.rs:30:1
╼ taskdump::pending::{{closure}} at backtrace/examples/taskdump.rs:15:1

Minimizing Overhead

To minimize overhead, ensure that futures you spawn with your async runtime are marked with #[framed].

In other words, avoid doing this:

tokio::spawn(async {
    foo().await;
    bar().await;
}).await;

#[async_backtrace::framed] async fn foo() {}
#[async_backtrace::framed] async fn bar() {}

...and prefer doing this:

tokio::spawn(async_backtrace::location!().frame(async {
    foo().await;
    bar().await;
})).await;

#[async_backtrace::framed] async fn foo() {}
#[async_backtrace::framed] async fn bar() {}

Estimating Overhead

To estimate the overhead of adopting #[framed] in your application, refer to the benchmarks and interpretive guidance in ./backtrace/benches/frame_overhead.rs. You can run these benchmarks with cargo bench.

License

This project is licensed under the MIT license.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in async-backtrace by you, shall be licensed as MIT, without any additional terms or conditions.

tokio-rs/async-backtrace

tokio-rs

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