tracing-timing 0.1.0

Inter-event timing metrics on top of tracing.

This crate provides a tracing::Subscriber that keeps statistics on inter-event timing information. More concretely, given code like this:

use tracing::*;
use tracing_timing::{Builder, Histogram};
let subscriber = Builder::from(|| Histogram::new_with_max(1_000_000, 2).unwrap()).build();
let dispatcher = Dispatch::new(subscriber);
dispatcher::with_default(&dispatcher, || {
    trace_span!("request").in_scope(|| {
        // do a little bit of work
        trace!("fast");
        // do a lot of work
        trace!("slow");
    })
});

You can produce something like this:

fast:
  50µs |
 100µs |
 150µs | ****
 200µs | ************
 250µs | *************
 300µs | *****
 350µs | ****
 400µs | *
 450µs |
 500µs |

slow:
 550µs |
 600µs |
 650µs | ******
 700µs | **********************
 750µs | *********
 800µs | **
 850µs | *
 900µs |

When TimingSubscriber is used as the tracing::Dispatch, the time between each event in a span is measured using quanta, and is recorded in "high dynamic range histograms" using hdrhistogram's multi-threaded recording facilities. The recorded timing information is grouped using the SpanGroup and EventGroup traits, allowing you to combine recorded statistics across spans and events.