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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
use std::collections::HashMap;
use crate::error_recording::{record_error, ErrorType};
use crate::histogram::{Functional, Histogram};
use crate::metrics::time_unit::TimeUnit;
use crate::metrics::{DistributionData, Metric, MetricType};
use crate::storage::StorageManager;
use crate::CommonMetricData;
use crate::Glean;
// The base of the logarithm used to determine bucketing
const LOG_BASE: f64 = 2.0;
// The buckets per each order of magnitude of the logarithm.
const BUCKETS_PER_MAGNITUDE: f64 = 8.0;
// Maximum time, which means we retain a maximum of 316 buckets.
// It is automatically adjusted based on the `time_unit` parameter
// so that:
//
// - `nanosecond` - 10 minutes
// - `microsecond` - ~6.94 days
// - `millisecond` - ~19 years
const MAX_SAMPLE_TIME: u64 = 1000 * 1000 * 1000 * 60 * 10;
/// Identifier for a running timer.
pub type TimerId = u64;
#[derive(Debug, Clone)]
struct Timings {
next_id: TimerId,
start_times: HashMap<TimerId, u64>,
}
/// Track different running timers, identified by a `TimerId`.
impl Timings {
/// Create a new timing manager.
fn new() -> Self {
Self {
next_id: 0,
start_times: HashMap::new(),
}
}
/// Start a new timer and set it to the `start_time`.
/// Multiple timers can run simultaneously.
///
/// Returns a new [`TimerId`] identifying the timer.
fn set_start(&mut self, start_time: u64) -> TimerId {
let id = self.next_id;
self.next_id += 1;
self.start_times.insert(id, start_time);
id
}
/// Stop the timer and return the elapsed time.
///
/// Returns an error if the `id` does not correspond to a running timer.
/// Returns an error if the stop time is before the start time.
///
/// ## Note
///
/// This API exists to satisfy the FFI requirements, where the clock is handled on the
/// application side and passed in as a timestamp.
fn set_stop(&mut self, id: TimerId, stop_time: u64) -> Result<u64, (ErrorType, &str)> {
let start_time = match self.start_times.remove(&id) {
Some(start_time) => start_time,
None => return Err((ErrorType::InvalidState, "Timing not running")),
};
let duration = match stop_time.checked_sub(start_time) {
Some(duration) => duration,
None => {
return Err((
ErrorType::InvalidValue,
"Timer stopped with negative duration",
))
}
};
Ok(duration)
}
/// Cancel and remove the timer.
fn cancel(&mut self, id: TimerId) {
self.start_times.remove(&id);
}
}
/// A timing distribution metric.
///
/// Timing distributions are used to accumulate and store time measurement, for analyzing distributions of the timing data.
#[derive(Debug)]
pub struct TimingDistributionMetric {
meta: CommonMetricData,
time_unit: TimeUnit,
timings: Timings,
}
/// Create a snapshot of the histogram with a time unit.
///
/// The snapshot can be serialized into the payload format.
pub(crate) fn snapshot(hist: &Histogram<Functional>) -> DistributionData {
DistributionData {
// **Caution**: This cannot use `Histogram::snapshot_values` and needs to use the more
// specialized snapshot function.
values: hist.snapshot(),
sum: hist.sum(),
}
}
impl MetricType for TimingDistributionMetric {
fn meta(&self) -> &CommonMetricData {
&self.meta
}
fn meta_mut(&mut self) -> &mut CommonMetricData {
&mut self.meta
}
}
// IMPORTANT:
//
// When changing this implementation, make sure all the operations are
// also declared in the related trait in `../traits/`.
impl TimingDistributionMetric {
/// Creates a new timing distribution metric.
pub fn new(meta: CommonMetricData, time_unit: TimeUnit) -> Self {
Self {
meta,
time_unit,
timings: Timings::new(),
}
}
/// Starts tracking time for the provided metric.
///
/// This records an error if it’s already tracking time (i.e.
/// [`set_start`](TimingDistributionMetric::set_start) was already called with no
/// corresponding [`set_stop_and_accumulate`](TimingDistributionMetric::set_stop_and_accumulate)): in
/// that case the original start time will be preserved.
///
/// # Arguments
///
/// * `start_time` - Timestamp in nanoseconds.
///
/// # Returns
///
/// A unique [`TimerId`] for the new timer.
pub fn set_start(&mut self, start_time: u64) -> TimerId {
self.timings.set_start(start_time)
}
/// Stops tracking time for the provided metric and associated timer id.
///
/// Adds a count to the corresponding bucket in the timing distribution.
/// This will record an error if no
/// [`set_start`](TimingDistributionMetric::set_start) was called.
///
/// # Arguments
///
/// * `id` - The [`TimerId`] to associate with this timing. This allows
/// for concurrent timing of events associated with different ids to the
/// same timespan metric.
/// * `stop_time` - Timestamp in nanoseconds.
pub fn set_stop_and_accumulate(&mut self, glean: &Glean, id: TimerId, stop_time: u64) {
// Duration is in nanoseconds.
let mut duration = match self.timings.set_stop(id, stop_time) {
Err((err_type, err_msg)) => {
record_error(glean, &self.meta, err_type, err_msg, None);
return;
}
Ok(duration) => duration,
};
let min_sample_time = self.time_unit.as_nanos(1);
let max_sample_time = self.time_unit.as_nanos(MAX_SAMPLE_TIME);
duration = if duration < min_sample_time {
// If measurement is less than the minimum, just truncate. This is
// not recorded as an error.
min_sample_time
} else if duration > max_sample_time {
let msg = format!(
"Sample is longer than the max for a time_unit of {:?} ({} ns)",
self.time_unit, max_sample_time
);
record_error(glean, &self.meta, ErrorType::InvalidOverflow, msg, None);
max_sample_time
} else {
duration
};
if !self.should_record(glean) {
return;
}
glean
.storage()
.record_with(glean, &self.meta, |old_value| match old_value {
Some(Metric::TimingDistribution(mut hist)) => {
hist.accumulate(duration);
Metric::TimingDistribution(hist)
}
_ => {
let mut hist = Histogram::functional(LOG_BASE, BUCKETS_PER_MAGNITUDE);
hist.accumulate(duration);
Metric::TimingDistribution(hist)
}
});
}
/// Aborts a previous [`set_start`](TimingDistributionMetric::set_start)
/// call. No error is recorded if no
/// [`set_start`](TimingDistributionMetric.set_start) was called.
///
/// # Arguments
///
/// * `id` - The [`TimerId`] to associate with this timing. This allows
/// for concurrent timing of events associated with different ids to the
/// same timing distribution metric.
pub fn cancel(&mut self, id: TimerId) {
self.timings.cancel(id);
}
/// Accumulates the provided signed samples in the metric.
///
/// This is required so that the platform-specific code can provide us with
/// 64 bit signed integers if no `u64` comparable type is available. This
/// will take care of filtering and reporting errors for any provided negative
/// sample.
///
/// Please note that this assumes that the provided samples are already in
/// the "unit" declared by the instance of the metric type (e.g. if the
/// instance this method was called on is using [`TimeUnit::Second`], then
/// `samples` are assumed to be in that unit).
///
/// # Arguments
///
/// * `samples` - The vector holding the samples to be recorded by the metric.
///
/// ## Notes
///
/// Discards any negative value in `samples` and report an [`ErrorType::InvalidValue`]
/// for each of them. Reports an [`ErrorType::InvalidOverflow`] error for samples that
/// are longer than `MAX_SAMPLE_TIME`.
pub fn accumulate_samples_signed(&mut self, glean: &Glean, samples: Vec<i64>) {
if !self.should_record(glean) {
return;
}
let mut num_negative_samples = 0;
let mut num_too_long_samples = 0;
let max_sample_time = self.time_unit.as_nanos(MAX_SAMPLE_TIME);
glean.storage().record_with(glean, &self.meta, |old_value| {
let mut hist = match old_value {
Some(Metric::TimingDistribution(hist)) => hist,
_ => Histogram::functional(LOG_BASE, BUCKETS_PER_MAGNITUDE),
};
for &sample in samples.iter() {
if sample < 0 {
num_negative_samples += 1;
} else {
let mut sample = sample as u64;
// Check the range prior to converting the incoming unit to
// nanoseconds, so we can compare against the constant
// MAX_SAMPLE_TIME.
if sample == 0 {
sample = 1;
} else if sample > MAX_SAMPLE_TIME {
num_too_long_samples += 1;
sample = MAX_SAMPLE_TIME;
}
sample = self.time_unit.as_nanos(sample);
hist.accumulate(sample);
}
}
Metric::TimingDistribution(hist)
});
if num_negative_samples > 0 {
let msg = format!("Accumulated {} negative samples", num_negative_samples);
record_error(
glean,
&self.meta,
ErrorType::InvalidValue,
msg,
num_negative_samples,
);
}
if num_too_long_samples > 0 {
let msg = format!(
"{} samples are longer than the maximum of {}",
num_too_long_samples, max_sample_time
);
record_error(
glean,
&self.meta,
ErrorType::InvalidOverflow,
msg,
num_too_long_samples,
);
}
}
/// Accumulates the provided samples in the metric.
///
/// # Arguments
///
/// * `samples` - A list of samples recorded by the metric.
/// Samples must be in nanoseconds.
/// ## Notes
///
/// Reports an [`ErrorType::InvalidOverflow`] error for samples that
/// are longer than `MAX_SAMPLE_TIME`.
pub fn accumulate_raw_samples_nanos(&mut self, glean: &Glean, samples: &[u64]) {
if !self.should_record(glean) {
return;
}
let mut num_too_long_samples = 0;
let min_sample_time = self.time_unit.as_nanos(1);
let max_sample_time = self.time_unit.as_nanos(MAX_SAMPLE_TIME);
glean.storage().record_with(glean, &self.meta, |old_value| {
let mut hist = match old_value {
Some(Metric::TimingDistribution(hist)) => hist,
_ => Histogram::functional(LOG_BASE, BUCKETS_PER_MAGNITUDE),
};
for &sample in samples.iter() {
let mut sample = sample;
if sample < min_sample_time {
sample = min_sample_time;
} else if sample > max_sample_time {
num_too_long_samples += 1;
sample = max_sample_time;
}
// `sample` is in nanoseconds.
hist.accumulate(sample);
}
Metric::TimingDistribution(hist)
});
if num_too_long_samples > 0 {
let msg = format!(
"{} samples are longer than the maximum of {}",
num_too_long_samples, max_sample_time
);
record_error(
glean,
&self.meta,
ErrorType::InvalidOverflow,
msg,
num_too_long_samples,
);
}
}
/// **Test-only API (exported for FFI purposes).**
///
/// Gets the currently stored value as an integer.
///
/// This doesn't clear the stored value.
pub fn test_get_value(&self, glean: &Glean, storage_name: &str) -> Option<DistributionData> {
match StorageManager.snapshot_metric_for_test(
glean.storage(),
storage_name,
&self.meta.identifier(glean),
self.meta.lifetime,
) {
Some(Metric::TimingDistribution(hist)) => Some(snapshot(&hist)),
_ => None,
}
}
/// **Test-only API (exported for FFI purposes).**
///
/// Gets the currently-stored histogram as a JSON String of the serialized value.
///
/// This doesn't clear the stored value.
pub fn test_get_value_as_json_string(
&self,
glean: &Glean,
storage_name: &str,
) -> Option<String> {
self.test_get_value(glean, storage_name)
.map(|snapshot| serde_json::to_string(&snapshot).unwrap())
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn can_snapshot() {
use serde_json::json;
let mut hist = Histogram::functional(2.0, 8.0);
for i in 1..=10 {
hist.accumulate(i);
}
let snap = snapshot(&hist);
let expected_json = json!({
"sum": 55,
"values": {
"1": 1,
"2": 1,
"3": 1,
"4": 1,
"5": 1,
"6": 1,
"7": 1,
"8": 1,
"9": 1,
"10": 1,
"11": 0,
},
});
assert_eq!(expected_json, json!(snap));
}
#[test]
fn can_snapshot_sparse() {
use serde_json::json;
let mut hist = Histogram::functional(2.0, 8.0);
hist.accumulate(1024);
hist.accumulate(1024);
hist.accumulate(1116);
hist.accumulate(1448);
let snap = snapshot(&hist);
let expected_json = json!({
"sum": 4612,
"values": {
"1024": 2,
"1116": 1,
"1217": 0,
"1327": 0,
"1448": 1,
"1579": 0,
},
});
assert_eq!(expected_json, json!(snap));
}
}