tokio-rs/tokio
1
0
Fork 0
mirror of https://github.com/tokio-rs/tokio.git synced 2026-08-19 00:00:09 +02:00
Code Issues Packages Projects Releases Wiki Activity

tracing: replace future names with spawn locations in task spans (#3074)

Browse Source 
## Motivation

Currently, the per-task `tracing` spans generated by tokio's `tracing`
feature flag include the `std::any::type_name` of the future that was
spawned. When future combinators and/or libraries like Tower are in use,
these future names can get _quite_ long. Furthermore, when formatting
the `tracing` spans with their parent spans as context, any other task
spans in the span context where the future was spawned from can _also_
include extremely long future names.

In some cases, this can result in extremely high memory use just to
store the future names. For example, in Linkerd, when we enable
`tokio=trace` to enable the task spans, there's a spawned task whose
future name is _232990 characters long_. A proxy with only 14 spawned
tasks generates a task list that's over 690 KB. Enabling task spans
under load results in the process getting OOM killed very quickly.

## Solution

This branch removes future type names from the spans generated by
`spawn`. As a replacement, to allow identifying which `spawn` call a
span corresponds to, the task span now contains the source code location
where `spawn` was called, when the compiler supports the
`#[track_caller]` attribute. Since `track_caller` was stabilized in Rust
1.46.0, and our minimum supported Rust version is 1.45.0, we can't
assume that `#[track_caller]` is always available. Instead, we have a
RUSTFLAGS cfg, `tokio_track_caller`, that guards whether or not we use
it. I've also added a `build.rs` that detects the compiler minor
version, and sets the cfg flag automatically if the current compiler
version is >= 1.46. This means users shouldn't have to enable
`tokio_track_caller` manually.

Here's the trace output from the `chat` example, before this change:
![Screenshot_20201030_110157](https://user-images.githubusercontent.com/2796466/97741071-6d408800-1a9f-11eb-9ed6-b25e72f58c7b.png)
...and after:
![Screenshot_20201030_110303](https://user-images.githubusercontent.com/2796466/97741112-7e899480-1a9f-11eb-9197-c5a3f9ea1c05.png)

Closes #3073

Signed-off-by: Eliza Weisman <[email protected]>
This commit is contained in:
Eliza Weisman
2020-11-01 10:48:44 -08:00
committed by GitHub
parent 2b23aa7389
commit fede3db76a
8 changed files with 63 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tokio/Cargo.toml
+5 -2
View File
@@ -102,7 +102,7 @@ mio = { version = "0.7.3", optional = true }
num_cpus = { version = "1.8.0", optional = true }
parking_lot = { version = "0.11.0", optional = true } # Not in full
slab = { version = "0.4.1", optional = true }
tracing = { version = "0.1.16", default-features = false, features = ["std"], optional = true } # Not in full
tracing = { version = "0.1.21", default-features = false, features = ["std"], optional = true } # Not in full
[target.'cfg(unix)'.dependencies]
libc = { version = "0.2.42", optional = true }
@@ -126,9 +126,12 @@ tempfile = "3.1.0"
[target.'cfg(loom)'.dev-dependencies]
loom = { version = "0.3.5", features = ["futures", "checkpoint"] }
[build-dependencies]
autocfg = "1" # Needed for conditionally enabling `track-caller`
[package.metadata.docs.rs]
all-features = true
rustdoc-args = ["--cfg", "docsrs"]
[package.metadata.playground]
features = ["full"]
features = ["full"]
tokio/build.rs
+22
View File
@@ -0,0 +1,22 @@
use autocfg::AutoCfg;
fn main() {
match AutoCfg::new() {
Ok(ac) => {
// The #[track_caller] attribute was stabilized in rustc 1.46.0.
if ac.probe_rustc_version(1, 46) {
autocfg::emit("tokio_track_caller")
}
}
Err(e) => {
// If we couldn't detect the compiler version and features, just
// print a warning. This isn't a fatal error: we can still build
// Tokio, we just can't enable cfgs automatically.
println!(
"cargo:warning=tokio: failed to detect compiler features: {}",
e
);
}
}
}
tokio/src/runtime/handle.rs
+14 -1
View File
@@ -39,13 +39,26 @@ impl Handle {
// context::enter(self.clone(), f)
// }
/// Run the provided function on an executor dedicated to blocking operations.
/// Run the provided function on an executor dedicated to blocking
/// operations.
#[cfg_attr(tokio_track_caller, track_caller)]
pub(crate) fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R>
where
F: FnOnce() -> R + Send + 'static,
{
#[cfg(feature = "tracing")]
let func = {
#[cfg(tokio_track_caller)]
let location = std::panic::Location::caller();
#[cfg(tokio_track_caller)]
let span = tracing::trace_span!(
target: "tokio::task",
"task",
kind = %"blocking",
function = %std::any::type_name::<F>(),
spawn.location = %format_args!("{}:{}:{}", location.file(), location.line(), location.column()),
);
#[cfg(not(tokio_track_caller))]
let span = tracing::trace_span!(
target: "tokio::task",
"task",
tokio/src/runtime/mod.rs
+4
View File
@@ -357,11 +357,14 @@ cfg_rt! {
/// });
/// # }
/// ```
#[cfg_attr(tokio_track_caller, track_caller)]
pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
where
F: Future + Send + 'static,
F::Output: Send + 'static,
{
#[cfg(feature = "tracing")]
let future = crate::util::trace::task(future, "task");
match &self.kind {
#[cfg(feature = "rt-multi-thread")]
Kind::ThreadPool(exec) => exec.spawn(future),
@@ -385,6 +388,7 @@ cfg_rt! {
/// println!("now running on a worker thread");
/// });
/// # }
#[cfg_attr(tokio_track_caller, track_caller)]
pub fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R>
where
F: FnOnce() -> R + Send + 'static,
tokio/src/task/blocking.rs
+1
View File
@@ -104,6 +104,7 @@ cfg_rt_multi_thread! {
/// # Ok(())
/// # }
/// ```
#[cfg_attr(tokio_track_caller, track_caller)]
pub fn spawn_blocking<F, R>(f: F) -> JoinHandle<R>
where
F: FnOnce() -> R + Send + 'static,
tokio/src/task/local.rs
+2
View File
@@ -190,6 +190,7 @@ cfg_rt! {
/// }).await;
/// }
/// ```
#[cfg_attr(tokio_track_caller, track_caller)]
pub fn spawn_local<F>(future: F) -> JoinHandle<F::Output>
where
F: Future + 'static,
@@ -273,6 +274,7 @@ impl LocalSet {
/// }
/// ```
/// [`spawn_local`]: fn@spawn_local
#[cfg_attr(tokio_track_caller, track_caller)]
pub fn spawn_local<F>(&self, future: F) -> JoinHandle<F::Output>
where
F: Future + 'static,
tokio/src/task/spawn.rs
+1
View File
@@ -122,6 +122,7 @@ cfg_rt! {
/// ```text
/// error[E0391]: cycle detected when processing `main`
/// ```
#[cfg_attr(tokio_track_caller, track_caller)]
pub fn spawn<T>(task: T) -> JoinHandle<T::Output>
where
T: Future + Send + 'static,
tokio/src/util/trace.rs
+14 -34
View File
@@ -1,47 +1,27 @@
cfg_trace! {
cfg_rt! {
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
use pin_project_lite::pin_project;
use tracing::Span;
pin_project! {
/// A future that has been instrumented with a `tracing` span.
#[derive(Debug, Clone)]
pub(crate) struct Instrumented<T> {
#[pin]
inner: T,
span: Span,
}
}
impl<T: Future> Future for Instrumented<T> {
type Output = T::Output;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let this = self.project();
let _enter = this.span.enter();
this.inner.poll(cx)
}
}
impl<T> Instrumented<T> {
pub(crate) fn new(inner: T, span: Span) -> Self {
Self { inner, span }
}
}
pub(crate) use tracing::instrument::Instrumented;
#[inline]
#[cfg_attr(tokio_track_caller, track_caller)]
pub(crate) fn task<F>(task: F, kind: &'static str) -> Instrumented<F> {
use tracing::instrument::Instrument;
#[cfg(tokio_track_caller)]
let location = std::panic::Location::caller();
#[cfg(tokio_track_caller)]
let span = tracing::trace_span!(
target: "tokio::task",
"task",
%kind,
future = %std::any::type_name::<F>(),
spawn.location = %format_args!("{}:{}:{}", location.file(), location.line(), location.column()),
);
Instrumented::new(task, span)
#[cfg(not(tokio_track_caller))]
let span = tracing::trace_span!(
target: "tokio::task",
"task",
%kind,
);
task.instrument(span)
}
}
}