Struct Trace 

pub struct Trace { /* private fields */ }

Joins each request to its trace, and puts the trace on the log line.

Outermost in the global stack, so every log emitted while handling the request carries the trace id — including the ones from middleware that rejected it, which are the lines you most want to find later.

MiddlewareStack::new().push(Trace::new()).push(RecordMetrics::new(metrics))

What it does without an exporter

Everything except send spans anywhere. The trace id is on the request, on the response and on every log line, so a request can be followed across services by grepping — which is most of the value, and it costs no dependency. The otlp feature adds the exporter.

Implementations

impl Trace

pub fn new() -> Trace

Sampling everything, and echoing the header back.

pub fn sampling(self, sample: bool) -> Trace

Whether to sample a trace this service starts.

Only applies when there is no incoming traceparent: a decision made upstream is honoured, because a trace sampled in half its services is a trace with holes in it.

pub fn respond_with_header(self, respond: bool) -> Trace

Whether to return traceparent on the response.

On by default, and it is what lets somebody paste a trace id from a browser’s network tab into a trace viewer. Turn it off if you would rather not tell a client your trace ids.

Trait Implementations

impl Default for Trace

fn default() -> Trace

Returns the “default value” for a type.

impl Middleware for Trace

fn handle<'life0, 'async_trait>( &'life0 self, request: Request, next: Next, ) -> Pin<Box<dyn Future<Output = Response> + Send + 'async_trait>>

where 'life0: 'async_trait, Trace: 'async_trait,

Handle the request, optionally calling next.

fn name(&self) -> &'static str

A label for diagnostics and route:list.