Function setup_with_sampler

pub fn setup_with_sampler<S: Fn(&SpanCtxt) -> bool + Send + Sync + 'static>(
    sampler: S,
) -> Setup<DefaultEmitter, TraceparentFilter<S>, TraceparentCtxt<DefaultCtxt>>

Start a builder for a distributed-trace-aware pipeline with a sampler.

The sampler will be called once for each trace when it’s started. If the sampler returns true, the trace will be emitted. If the sampler returns false, the trace will be discarded.

use std::sync::atomic::{AtomicUsize, Ordering};

fn main() {
    let rt = emit_traceparent::setup_with_sampler({
        let counter = AtomicUsize::new(0);

        move |_| {
            // Sample 1 in every 10 traces
            counter.fetch_add(1, Ordering::Relaxed) % 10 == 0
        }
    })
    .emit_to(emit_term::stdout())
    .init();

    // Your app code goes here

    rt.blocking_flush(std::time::Duration::from_secs(30));
}

Note that other events emitted within an unsampled trace will still be emitted. You can add the in_sampled_trace_filter filter to filter out events in unsampled traces:

use std::sync::atomic::{AtomicUsize, Ordering};

fn main() {
    let rt = emit_traceparent::setup_with_sampler({
        let counter = AtomicUsize::new(0);

        move |_| {
            // Sample 1 in every 10 traces
            counter.fetch_add(1, Ordering::Relaxed) % 10 == 0
        }
    })
    // The `true` here tells us to include events outside traces
    // If we pass `false` then any event outside a trace will be discarded
    .and_emit_when(emit_traceparent::in_sampled_trace_filter(true))
    .emit_to(emit_term::stdout())
    .init();

    // Your app code goes here

    rt.blocking_flush(std::time::Duration::from_secs(30));
}

The true parameter passed to in_sampled_trace_filter here includes events that aren’t in any trace. Passing false will also filter out events that aren’t part of any trace.