How to use Rusts tracing_distributed - html

Question

I am trying to use the Rust tracing_distributed package, but I am getting strange and unhelpful errors when using it, and I am assuming I am using it wrong, but there is no documentation and there are no examples about how to use it. Here is an example of what I'm trying to do :
let trace = tracing_distributed::register_dist_tracing_root(traceId, remote_parent_span_id));
println!("trace value: {:?}", trace);
// the result of trace is: Err(NoEnabledSpan)
I have tried passing a few things in as the traceID and remote_parent_span_id including:
traceId = remote_parent_span_id = Some(tracing::Span::current())
As well as:
traceId = Some(tracing::Span::current())
remote_parent_span_id = ~someParentRequestIdGeneratedUpstream~
I know that the current span is not disabled from trying:
let span = tracing::Span::current();
if span.is_disabled() {
println!("CURRENT SPAN DISABELED");
}
So this leads me to think that the issue is coming from not having the subscriber set properly. I am trying to set the subscriber in an init function which is called before this function which looks like this:
let subscriber = tracing_subscriber::registry() // provide underlying span data store
.with(
tracing_subscriber::fmt::layer()
.json()
.with_span_events(FmtSpan::ACTIVE)
.event_format(stackdriver::StackDriverEventFormat::default())
.with_filter(tracing_subscriber::filter::dynamic_filter_fn(
move |m, c| filter_layer.enabled(m, c.to_owned()),
)),
);
let _ = tracing::subscriber::set_global_default(subscriber)
.map_err(|_err| eprintln!("Unable to set global default subscriber"));
Would anyone be willing to provide me with an example of how to use this library? Or can anyone see what I'm doing wrong here? I have tried everything I can think of.

Answer 1

tracing-distributed has a test which demonstrates how to create and use TelemetryLayer.
I made a demo based on it. In this demo, NoEnabledSpan may be caused by missing #[instrument], which creates a Span for function foo. Hope this will help you find the actual cause.
Also tracing-honeycomb is a great use case for tracing-distributed, better check it out.
use std::sync::{Arc, Mutex};
use tracing::{Id, info};
use tracing::instrument;
use tracing_distributed::{Event, Span, Telemetry, TelemetryLayer};
use tracing_subscriber::layer::SubscriberExt;
use tracing_subscriber::registry;
#[derive(Default, Debug)]
pub struct BlackholeVisitor;
#[derive(PartialEq, Eq, Hash, Copy, Clone, Debug)]
pub struct TraceId(pub(crate) u128);
type SpanId = tracing::Id;
impl tracing::field::Visit for BlackholeVisitor {
fn record_debug(&mut self, _: &tracing::field::Field, _: &dyn std::fmt::Debug) {}
}
/// Mock telemetry capability
pub struct TestTelemetry {
spans: Arc<Mutex<Vec<Span<BlackholeVisitor, SpanId, TraceId>>>>,
events: Arc<Mutex<Vec<Event<BlackholeVisitor, SpanId, TraceId>>>>,
}
impl TestTelemetry {
pub fn new(
spans: Arc<Mutex<Vec<Span<BlackholeVisitor, SpanId, TraceId>>>>,
events: Arc<Mutex<Vec<Event<BlackholeVisitor, SpanId, TraceId>>>>,
) -> Self {
TestTelemetry { spans, events }
}
}
impl Telemetry for TestTelemetry {
type Visitor = BlackholeVisitor;
type TraceId = TraceId;
type SpanId = SpanId;
fn mk_visitor(&self) -> Self::Visitor {
BlackholeVisitor
}
fn report_span(&self, span: Span<BlackholeVisitor, SpanId, TraceId>) {
// succeed or die. failure is unrecoverable (mutex poisoned)
let mut spans = self.spans.lock().unwrap();
spans.push(span);
}
fn report_event(&self, event: Event<BlackholeVisitor, SpanId, TraceId>) {
// succeed or die. failure is unrecoverable (mutex poisoned)
let mut events = self.events.lock().unwrap();
events.push(event);
}
}
#[instrument]
fn foo() {
let trace = tracing_distributed::register_dist_tracing_root(TraceId(123), Option::<Id>::None);
println!("trace value: {:?}", trace);
info!("test");
}
fn main() {
let spans = Arc::new(Mutex::new(Vec::new()));
let events = Arc::new(Mutex::new(Vec::new()));
let cap = TestTelemetry::new(spans.clone(), events.clone());
let telemetry_layer = TelemetryLayer::new("test_svc_name", cap, |x| x);
let subscriber = registry::Registry::default()
.with(tracing_subscriber::fmt::Layer::default())
.with(telemetry_layer);
// dbg!(&subscriber);
tracing::subscriber::set_global_default(subscriber).expect("setting global default failed");
foo();
dbg!(&spans);
dbg!(&events);
}
crate versions:
tracing = "0.1.32"
tracing-distributed = "0.4.0"
tracing-subscriber = "0.3.10"