mirror of https://github.com/fralalonde/dipstick
182 lines
5.9 KiB
Rust
182 lines
5.9 KiB
Rust
use std::mem;
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use core::*;
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use core::Kind::*;
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use std::sync::atomic::AtomicUsize;
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use std::sync::atomic::Ordering::*;
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use std::usize;
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use self::ScoreType::*;
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#[derive(Debug, Clone, Copy)]
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/// Possibly aggregated scores.
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pub enum ScoreType {
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/// Number of times the metric was used.
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Count(u64),
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/// Sum of metric values reported.
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Sum(u64),
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/// Biggest value reported.
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Max(u64),
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/// Smallest value reported.
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Min(u64),
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/// Average value (hit count / sum, non-atomic)
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Mean(f64),
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/// Mean rate (hit count / period length in seconds, non-atomic)
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Rate(f64),
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}
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/// A snapshot of multiple scores for a single metric.
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pub type ScoreSnapshot = (Kind, String, Vec<ScoreType>);
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/// A metric that holds aggregated values.
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/// Some fields are kept public to ease publishing.
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#[derive(Debug)]
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pub struct Scoreboard {
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namespace: Namespace,
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/// The kind of metric.
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kind: Kind,
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/// The metric's name.
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name: String,
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scores: [AtomicUsize; 5],
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}
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impl Scoreboard {
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/// Create a new Scoreboard to track summary values of a metric
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pub fn new(namespace: Namespace, kind: Kind, name: String) -> Self {
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Scoreboard {
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namespace,
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kind,
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name,
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scores: unsafe { mem::transmute(Scoreboard::blank(accurate_clock_micros() as usize)) },
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}
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}
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#[inline]
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fn blank(now: usize) -> [usize; 5] {
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[now, 0, 0, usize::MIN, usize::MAX]
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}
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/// Update scores with new value
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pub fn update(&self, value: Value) -> () {
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// TODO report any concurrent updates / resets for measurement of contention
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let value = value as usize;
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self.scores[1].fetch_add(1, AcqRel);
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match self.kind {
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Marker => {}
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_ => {
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// optimization - these fields are unused for Marker stats
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self.scores[2].fetch_add(value, AcqRel);
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swap_if(&self.scores[3], value, |new, current| new > current);
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swap_if(&self.scores[4], value, |new, current| new < current);
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}
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}
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}
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/// Reset scores to zero, return previous values
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fn snapshot(&self, now: usize, scores: &mut [usize; 5]) -> bool {
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// NOTE copy timestamp, count AND sum _before_ testing for data to reduce concurrent discrepancies
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scores[0] = self.scores[0].swap(now, AcqRel);
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scores[1] = self.scores[1].swap(0, AcqRel);
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scores[2] = self.scores[2].swap(0, AcqRel);
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// if hit count is zero, then no values were recorded.
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if scores[1] == 0 {
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return false;
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}
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scores[3] = self.scores[3].swap(usize::MIN, AcqRel);
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scores[4] = self.scores[4].swap(usize::MAX, AcqRel);
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true
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}
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/// Map raw scores (if any) to applicable statistics
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pub fn reset(&self) -> Option<ScoreSnapshot> {
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let now: usize = accurate_clock_micros() as usize;
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let mut scores = Scoreboard::blank(now);
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if self.snapshot(now, &mut scores) {
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let duration_seconds = (now - scores[0]) as f64 / 1_000.0;
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let mut snapshot = Vec::new();
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match self.kind {
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Marker => {
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snapshot.push(Count(scores[1] as u64));
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snapshot.push(Rate(scores[1] as f64 / duration_seconds))
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}
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Gauge => {
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snapshot.push(Max(scores[3] as u64));
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snapshot.push(Min(scores[4] as u64));
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snapshot.push(Mean(scores[2] as f64 / scores[1] as f64));
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}
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Timer => {
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snapshot.push(Count(scores[1] as u64));
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snapshot.push(Sum(scores[2] as u64));
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snapshot.push(Max(scores[3] as u64));
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snapshot.push(Min(scores[4] as u64));
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snapshot.push(Mean(scores[2] as f64 / scores[1] as f64));
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// timer rate uses the COUNT of timer calls per second (not SUM)
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snapshot.push(Rate(scores[1] as f64 / duration_seconds))
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}
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Counter => {
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snapshot.push(Count(scores[1] as u64));
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snapshot.push(Sum(scores[2] as u64));
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snapshot.push(Max(scores[3] as u64));
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snapshot.push(Min(scores[4] as u64));
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snapshot.push(Mean(scores[2] as f64 / scores[1] as f64));
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// counter rate uses the SUM of values per second (e.g. to get bytes/s)
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snapshot.push(Rate(scores[2] as f64 / duration_seconds))
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}
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}
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Some((self.kind, self.name.clone(), snapshot))
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} else {
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None
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}
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}
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}
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/// Spinlock until success or clear loss to concurrent update.
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#[inline]
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fn swap_if(counter: &AtomicUsize, new_value: usize, compare: fn(usize, usize) -> bool) {
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let mut current = counter.load(Acquire);
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while compare(new_value, current) {
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if counter.compare_and_swap(current, new_value, Release) == new_value {
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// update successful
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break;
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}
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// race detected, retry
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current = counter.load(Acquire);
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}
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}
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#[cfg(feature = "bench")]
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mod bench {
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use super::*;
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use test;
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#[bench]
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fn bench_score_update_marker(b: &mut test::Bencher) {
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let metric = Scoreboard::new(ROOT_NS.clone(), Marker, "event_a".to_string());
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b.iter(|| test::black_box(metric.update(1)));
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}
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#[bench]
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fn bench_score_update_count(b: &mut test::Bencher) {
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let metric = Scoreboard::new(ROOT_NS.clone(), Counter, "event_a".to_string());
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b.iter(|| test::black_box(metric.update(4)));
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}
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#[bench]
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fn bench_score_empty_snapshot(b: &mut test::Bencher) {
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let metric = Scoreboard::new(ROOT_NS.clone(), Counter, "event_a".to_string());
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let mut scores = Scoreboard::blank(0);
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b.iter(|| test::black_box(metric.snapshot(0, &mut scores)));
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}
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}
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