tracing-texray 
First, a word of warning: This is alpha software. Don't run this in prod or anywhere where a panic would ruin your day.
tracing-texray is a tracing layer to introspect spans and events in plain text. By examine-ing a specific span, a full tree will be output when that span exits. Using code like the following (actual program elided):
fn main() {
// initialize & install as the global subscriber
tracing_texray::init();
// examine the `load_data` span:
tracing_texray::examine(tracing::info_span!("load_data")).in_scope(|| {
do_a_thing()
});
}
fn do_a_thing() {
// ...
}
You would see the following output printed to stderr:
load_data 52ms ├────────────────────────────────┤
download_results{uri: www.crates.io} 11ms ├─────┤
>URI resolved ┼
>connected ┼
compute_stats 10ms ├─────┤
render_response 6ms ├──┤
In cases where a more powerful solution like tracing-chrome is not required, tracing-texray can render lightweight timeline of what happened when.
Usage
tracing-texray combines two pieces: a global subscriber, and local span examination. By default, tracing-texray won't print anything—it just sits in the background. But: once a span is examine'd, tracing-texray will track the span and all of its children. When the span exits, span diagnostics will be printed to stderr (or another impl io::Write as configured).
First, the layer must be installed globally:
use std::time::Duration;
use tracing_texray::TeXRayLayer;
use tracing_subscriber::{Registry, EnvFilter, layer::SubscriberExt};
fn main() {
// Option A: Exclusively using tracing_texray:
tracing_texray::init();
// Option B: install the layer in combination with other layers, eg. tracing_subscriber::fmt:
let subscriber = Registry::default()
.with(EnvFilter::try_from_default_env().expect("invalid env filter"))
.with(tracing_subscriber::fmt::layer())
.with(
TeXRayLayer::new()
// by default, all metadata fields will be printed. If this is too noisy,
// fitler only the fields you care about
.only_show_fields(&["name", "operation", "service"])
// only print spans longer than a certain duration
.min_duration(Duration::from_millis(100)),
);
tracing::subscriber::set_global_default(subscriber).unwrap();
}
Next, wrap any spans you want to track with examine:
use tracing::info_span;
use tracing_texray::examine;
fn somewhere_deep_in_my_program() {
tracing_texray::examine(info_span!("do_a_thing")).in_scope(|| {
for id in 0..5 {
some_other_function(id);
}
})
}
fn some_other_function(id: usize) {
info_span!("inner_task", id = %id).in_scope(|| tracing::info!("buzz"));
// ...
}
When the do_a_thing span exits, output like the following will be printed:
do_a_thing 509μs ├───────────────────────────────────────────────────┤
inner_task{id: 0} 92μs ├────────┤
>buzz ┼
inner_task{id: 1} 36μs ├──┤
>buzz ┼
inner_task{id: 2} 35μs ├──┤
>buzz ┼
inner_task{id: 3} 36μs ├──┤
>buzz ┼
inner_task{id: 4} 35μs ├──┤
>buzz ┼
15 Nov 3, 2022
2 Dec 27, 2021
42 Dec 3, 2022
5 Oct 24, 2022
5 Oct 31, 2023
776 Jan 1, 2023
2 Aug 14, 2022
0 Dec 22, 2021
11 Aug 10, 2022
7 Oct 8, 2022
12 Dec 6, 2022
7 May 14, 2023
5 Jan 3, 2023
17 Jun 7, 2022
9 Nov 23, 2022
31 Jan 4, 2023
412 Oct 18, 2023
10 Sep 23, 2021