3 releases (breaking)
0.3.0 | Feb 23, 2022 |
---|---|
0.2.0 | Feb 21, 2022 |
0.1.0 | Jan 27, 2022 |
#10 in #tangle
71KB
1K
SLoC
trace-tools
Tracing and diagnostic tools for async, using tokio
and tracing
.
The crate consists of a few components:
- The
Observe
trait - A
tracing::Subscriber
implementation, as well as usefulLayer
s. - Diagnostic utilities (currently just one, in
Flamegrapher
). #[observe]
attribute procedural macro.
The Observe
trait
This trait provides the ability to wrap futures with an instrumentation span, similar to the tracing_futures::Instrument
trait. This span has some default properties that make it easy to register and filter in a subscriber:
tracing::trace_span!(
target: "trace_tools::observe",
"observed",
observed.name = <my_function_name>,
loc.file = <caller_file>,
loc.line = <caller_line>,
loc.col = <caller_column>,
);
Crucially, this span contains identical fields to those generated internally by tokio
for task spawns (when compiled with --cfg tokio_unstable
, which means that subscribers can interact with spans generated by Observe
in the same way that they can with tokio
s internal spans.
Subscriber implementation
trace-tools
provides a subscriber and two Layer
s for dealing with spans and events:
- Flamegraph layer: produces a folded stack file detailing instrumented span stacks (either instrumented internally by
tokio
or bytrace-tools
) that can be used to generate a flamegraph of all observed code. - Logging layer: allows
log
records to be converted intotracing
events, and recreates full logging functionality (equivalent tofern-logger
) within the subscriber itself, since it is impossible to set two loggers/subscribers at once. This means that logging remains consistent whether usingtrace-tools
or not. - Console layer (enabled by the
tokio-console
feature): builds aconsole_subscriber::ConsoleLayer
(from tokio'sconsole
project) to collect task metrics and broadcast them. With this layer enabled, you can run theconsole
binary and observe all asynchronous tasks in real-time. Note: only spans associated with tasks are observed in this way, not all spans;trace_tools::observe
spans will not appear.
The subscriber can be initialised through a builder that can either set the global subscriber or return a Layered
instance that can be further extended with more Layer
s.
Setting as the default subscriber:
// `Flamegrapher` handle returned, for building a flamegraph at the end of the run.
let flamegrapher = trace_tools::subscriber::build()
.with_flamegraph_layer(stack_filename)
.with_log_layer(log_config)
.init()?
.unwrap();
Returning a Layered
struct:
let (subscriber, flamegrapher) = trace_tools::subscriber::build()
.with_flamegraph_layer(stack_filename)
.with_log_layer(log_config)
.finish()?;
// Extend the subscriber with external layers.
let subscriber = subscriber.with(console_layer);
// Set the global subscriber.
subscriber.init();
Flamegrapher
Produces a flamegraph using the given folded stack file, using the inferno
crate.
let flamegrapher = trace_tools::subscriber::build()
.with_flamegraph_layer(stack_filename)
.init()?
.unwrap();
// Run some instrumented code...
// ...
// ...
// Programatically create the flamegraph file.
flamegrapher
.with_graph_file("flamegraph.svg")?
.write_flamegraph()?;
#[observe]
attribute
trace-tools
provides a simple attribute proc-macro for instrumenting functions and futures with a span that specifies the trace_tools::observe
target. The location fields in the span will describe the location of the tagged function or future, and the observed.name
field will specify the function name:
use trace_tools::observe;
#[observe]
pub async fn say_hello() {
println!("hello");
}
This is equivalent to the following:
trace_tools::Observe(say_hello(), "say_hello").await;
This macro can be used with regular, non-async
functions too, unlike the Observe
trait.
tokio-console
feature
The tokio-console
feature enables the console layer. Note that this makes use of unstable tokio
features in order to work. As such, this also crate must be built with RUSTFLAGS="--cfg tokio_unstable"
to use the feature.
Examples
There is an example for each layer in trace-tools/examples
. The flamegraph example produces this interactive graph:
Dependencies
~6–16MB
~213K SLoC