WIP

Author: davidbarsky

.gitignore

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+/target
+Cargo.lock

Cargo.toml

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+[package]
+name = "tracing-tree"
+version = "0.1.0"
+authors = ["David Barsky <me@davidbarsky.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+tracing = "0.1.11"
+tracing-subscriber = { git = "https://github.com/tokio-rs/tracing" }
+quanta = "0.3.1"
+termcolor = "1.0.5"

examples/basic.rs

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+use tracing::{info, instrument, span, Level};
+use tracing_subscriber::layer::SubscriberExt;
+use tracing_subscriber::{registry::Registry, Layer};
+use tracing_tree::TreeLayer;
+
+fn main() {
+    let subscriber = Registry::default().with(TreeLayer::default());
+    tracing::subscriber::set_global_default(subscriber).expect("Unable to set a global default");
+    call_a("david");
+}
+
+#[instrument]
+fn call_a(name: &str) {
+    info!(name, "got a name");
+    call_b(name)
+}
+
+#[instrument]
+fn call_b(name: &str) {
+    info!(name, "got a name");
+}

src/lib.rs

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+use quanta::Clock;
+use std::fmt::Debug;
+use tracing::{
+    span::{Attributes, Id, Record},
+    Event, Level, Metadata, Subscriber,
+};
+use tracing_subscriber::{
+    layer::{Context, Layer},
+    registry::LookupSpan,
+};
+
+#[derive(Debug, Default)]
+pub struct TreeLayer {
+    clock: Clock,
+}
+
+#[derive(Debug)]
+struct Data {
+    start: u64,
+    level: Level,
+}
+
+impl<S> Layer<S> for TreeLayer
+where
+    S: Subscriber + for<'span> LookupSpan<'span> + Debug,
+{
+    fn new_span(&self, attrs: &Attributes, id: &Id, ctx: Context<S>) {
+        let start = self.clock.now();
+        let level = attrs.metadata().level();
+        dbg!(attrs);
+        let data = Data {
+            start,
+            level: level.clone(),
+        };
+        let span = ctx.span(id).expect("in new_span but span does not exist");
+        span.extensions_mut().insert(data);
+    }
+
+    fn on_event(&self, event: &Event<'_>, _ctx: Context<S>) {
+        dbg!(event);
+    }
+
+    fn on_close(&self, id: Id, ctx: Context<S>) {
+        let end = self.clock.now();
+        let span = ctx.span(&id).expect("in on_close but span does not exist");
+        let mut ext = span.extensions_mut();
+        let data = ext
+            .get_mut::<Data>()
+            .expect("span does not have metric data");
+
+        let elapsed = self.clock.delta(data.start, end);
+    }
+}