tokio-rs/tracing

use futures::future::{self, Future};
use tracing::{debug, info, span, Level};
use tracing_futures::{Instrument, WithSubscriber};

use tracing::*;
use tracing_subscriber::layer::{Layer, Context};
use tracing::span::Attributes;

struct MyLayer;

impl<S: Subscriber> Layer<S> for MyLayer {
    fn new_span(&self, attrs: &Attributes<'_>, created: &Id, ctx: Context<'_, S>) {
        let span = ctx.current_span();
        dbg!(created);
    }

    fn on_close(&self, dropped: Id, _ctx: Context<'_, S>) {
        dbg!(dropped);
    }
}

fn parent() -> impl Future<Item = (), Error = ()> {
    futures::lazy({ || {
        child()
    }}).and_then(|futures| {
        info!("and_then");
        Ok(())
    }).instrument(span!(Level::INFO, "parent_task"))
}

fn child() -> impl Future<Item = (), Error = ()> {
    futures::lazy(|| {
        info!("from child");
        Ok(())
    }).instrument(span!(Level::INFO, "child_task"))
}

fn main() {
    let subscriber = tracing_subscriber::fmt::Subscriber::default();
    let subscriber = Layer::with_subscriber(MyLayer, subscriber);
    tracing::subscriber::set_global_default(subscriber).expect("failed to set");

    tokio::run(parent());
}