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use tracing::field;
use std::{error, fmt, sync::mpsc};
use tracing_tunnel::{TracingEvent, TracingEventSender};
#[derive(Debug)]
struct Overflow;
impl fmt::Display for Overflow {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(formatter, "integer overflow")
}
}
impl error::Error for Overflow {}
#[tracing::instrument(target = "fib", ret, err)]
fn compute(count: usize) -> Result<u64, Overflow> {
let (mut x, mut y) = (0_u64, 1_u64);
for i in 0..count {
tracing::debug!(target: "fib", i, current = x, "performing iteration");
(x, y) = (y, x.checked_add(y).ok_or(Overflow)?);
}
Ok(x)
}
const PHI: f64 = 1.618033988749895; // (1 + sqrt(5)) / 2
pub fn fib(count: usize) {
let span = tracing::info_span!("fib", approx = field::Empty);
let _entered = span.enter();
let approx = PHI.powi(count as i32) / 5.0_f64.sqrt();
let approx = approx.round();
span.record("approx", approx);
tracing::warn!(count, "count looks somewhat large");
match compute(count) {
Ok(result) => {
tracing::info!(result, "computed Fibonacci number");
}
Err(err) => {
tracing::error!(error = &err as &dyn error::Error, "computation failed");
}
}
}
pub fn record_events(count: usize) -> Vec<TracingEvent> {
let (events_sx, events_rx) = mpsc::sync_channel(256);
// ^ The channel capacity should allow for *all* events since we start collecting events
// after they all are emitted.
let sender = TracingEventSender::new(move |event| {
events_sx.send(event).unwrap();
});
tracing::subscriber::with_default(sender, || fib(count));
events_rx.iter().collect()
}
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