Add deserialization from Prometheus text format in metrics package #1582
Description
MetricCollection can be serialized/deserialized in JSON.
It can also be serialized into Prometheus text format:
pub trait PrometheusSerializable {
/// Convert the implementing type into a Prometheus exposition format string.
///
/// # Returns
///
/// A `String` containing the serialized representation.
fn to_prometheus(&self) -> String;
}
impl PrometheusSerializable for MetricCollection {
fn to_prometheus(&self) -> String {
self.counters
.metrics
.values()
.filter(|metric| !metric.is_empty())
.map(Metric::<Counter>::to_prometheus)
.chain(
self.gauges
.metrics
.values()
.filter(|metric| !metric.is_empty())
.map(Metric::<Gauge>::to_prometheus),
)
.collect::<Vec<String>>()
.join("\n\n")
}
}It would be helpful to add deserialization from Prometheus format, too.
One use case I see is to make some tests more expressive and easier to write/read:
#[cfg(test)]
mod tests {
use torrust_tracker_primitives::DurationSinceUnixEpoch;
use crate::aggregate::AggregateValue;
use crate::counter::Counter;
use crate::gauge::Gauge;
use crate::label::LabelSet;
use crate::metric::aggregate::sum::Sum;
use crate::metric::{Metric, MetricName};
use crate::metric_name;
use crate::sample::Sample;
use crate::sample_collection::SampleCollection;
struct MetricBuilder<T> {
sample_time: DurationSinceUnixEpoch,
name: MetricName,
samples: Vec<Sample<T>>,
}
impl<T> Default for MetricBuilder<T> {
fn default() -> Self {
Self {
sample_time: DurationSinceUnixEpoch::from_secs(1_743_552_000),
name: metric_name!("test_metric"),
samples: vec![],
}
}
}
impl<T> MetricBuilder<T> {
fn with_sample(mut self, value: T, label_set: &LabelSet) -> Self {
let sample = Sample::new(value, self.sample_time, label_set.clone());
self.samples.push(sample);
self
}
fn build(self) -> Metric<T> {
Metric::new(
self.name,
None,
None,
SampleCollection::new(self.samples).expect("invalid samples"),
)
}
}
fn counter_cases() -> Vec<(Metric<Counter>, LabelSet, AggregateValue)> {
// (metric, label set criteria, expected_aggregate_value)
vec![
// Metric with one sample without label set
(
MetricBuilder::default().with_sample(1.into(), &LabelSet::empty()).build(),
LabelSet::empty(),
1.0.into(),
),
// Metric with one sample with a label set
(
MetricBuilder::default()
.with_sample(1.into(), &[("l1", "l1_value")].into())
.build(),
[("l1", "l1_value")].into(),
1.0.into(),
),
// Metric with two samples, different label sets, sum all
(
MetricBuilder::default()
.with_sample(1.into(), &[("l1", "l1_value")].into())
.with_sample(2.into(), &[("l2", "l2_value")].into())
.build(),
LabelSet::empty(),
3.0.into(),
),
// Metric with two samples, different label sets, sum one
(
MetricBuilder::default()
.with_sample(1.into(), &[("l1", "l1_value")].into())
.with_sample(2.into(), &[("l2", "l2_value")].into())
.build(),
[("l1", "l1_value")].into(),
1.0.into(),
),
// Metric with two samples, same label key, different label values, sum by key
(
MetricBuilder::default()
.with_sample(1.into(), &[("l1", "l1_value"), ("la", "la_value")].into())
.with_sample(2.into(), &[("l1", "l1_value"), ("lb", "lb_value")].into())
.build(),
[("l1", "l1_value")].into(),
3.0.into(),
),
// Metric with two samples, different label values, sum by subkey
(
MetricBuilder::default()
.with_sample(1.into(), &[("l1", "l1_value"), ("la", "la_value")].into())
.with_sample(2.into(), &[("l1", "l1_value"), ("lb", "lb_value")].into())
.build(),
[("la", "la_value")].into(),
1.0.into(),
),
// Edge: Metric with no samples at all
(MetricBuilder::default().build(), LabelSet::empty(), 0.0.into()),
// Edge: Metric with samples but no matching labels
(
MetricBuilder::default()
.with_sample(5.into(), &[("foo", "bar")].into())
.build(),
[("not", "present")].into(),
0.0.into(),
),
// Edge: Metric with zero value
(
MetricBuilder::default()
.with_sample(0.into(), &[("l3", "l3_value")].into())
.build(),
[("l3", "l3_value")].into(),
0.0.into(),
),
// Edge: Metric with a very large value
(
MetricBuilder::default()
.with_sample(u64::MAX.into(), &LabelSet::empty())
.build(),
LabelSet::empty(),
#[allow(clippy::cast_precision_loss)]
(u64::MAX as f64).into(),
),
]
}
fn gauge_cases() -> Vec<(Metric<Gauge>, LabelSet, AggregateValue)> {
// (metric, label set criteria, expected_aggregate_value)
vec![
// Metric with one sample without label set
(
MetricBuilder::default().with_sample(1.0.into(), &LabelSet::empty()).build(),
LabelSet::empty(),
1.0.into(),
),
// Metric with one sample with a label set
(
MetricBuilder::default()
.with_sample(1.0.into(), &[("l1", "l1_value")].into())
.build(),
[("l1", "l1_value")].into(),
1.0.into(),
),
// Metric with two samples, different label sets, sum all
(
MetricBuilder::default()
.with_sample(1.0.into(), &[("l1", "l1_value")].into())
.with_sample(2.0.into(), &[("l2", "l2_value")].into())
.build(),
LabelSet::empty(),
3.0.into(),
),
// Metric with two samples, different label sets, sum one
(
MetricBuilder::default()
.with_sample(1.0.into(), &[("l1", "l1_value")].into())
.with_sample(2.0.into(), &[("l2", "l2_value")].into())
.build(),
[("l1", "l1_value")].into(),
1.0.into(),
),
// Metric with two samples, same label key, different label values, sum by key
(
MetricBuilder::default()
.with_sample(1.0.into(), &[("l1", "l1_value"), ("la", "la_value")].into())
.with_sample(2.0.into(), &[("l1", "l1_value"), ("lb", "lb_value")].into())
.build(),
[("l1", "l1_value")].into(),
3.0.into(),
),
// Metric with two samples, different label values, sum by subkey
(
MetricBuilder::default()
.with_sample(1.0.into(), &[("l1", "l1_value"), ("la", "la_value")].into())
.with_sample(2.0.into(), &[("l1", "l1_value"), ("lb", "lb_value")].into())
.build(),
[("la", "la_value")].into(),
1.0.into(),
),
// Edge: Metric with no samples at all
(MetricBuilder::default().build(), LabelSet::empty(), 0.0.into()),
// Edge: Metric with samples but no matching labels
(
MetricBuilder::default()
.with_sample(5.0.into(), &[("foo", "bar")].into())
.build(),
[("not", "present")].into(),
0.0.into(),
),
// Edge: Metric with zero value
(
MetricBuilder::default()
.with_sample(0.0.into(), &[("l3", "l3_value")].into())
.build(),
[("l3", "l3_value")].into(),
0.0.into(),
),
// Edge: Metric with negative values
(
MetricBuilder::default()
.with_sample((-2.0).into(), &[("l4", "l4_value")].into())
.with_sample(3.0.into(), &[("l5", "l5_value")].into())
.build(),
LabelSet::empty(),
1.0.into(),
),
// Edge: Metric with a very large value
(
MetricBuilder::default()
.with_sample(f64::MAX.into(), &LabelSet::empty())
.build(),
LabelSet::empty(),
f64::MAX.into(),
),
]
}
#[test]
fn test_counter_cases() {
for (idx, (metric, criteria, expected_value)) in counter_cases().iter().enumerate() {
let sum = metric.sum(criteria);
assert_eq!(
sum, *expected_value,
"at case {idx}, expected sum to be {expected_value}, got {sum}"
);
}
}
#[test]
fn test_gauge_cases() {
for (idx, (metric, criteria, expected_value)) in gauge_cases().iter().enumerate() {
let sum = metric.sum(criteria);
assert_eq!(
sum, *expected_value,
"at case {idx}, expected sum to be {expected_value}, got {sum}"
);
}
}
}For example, this:
// Metric with one sample with a label set
(
MetricBuilder::default()
.with_sample(1.into(), &[("l1", "l1_value")].into())
.build(),
[("l1", "l1_value")].into(),
1.0.into(),
),could be rewritten into:
// Metric with one sample with a label set
(
r#"test_metric{"l1"="li_value"} 1"
[("l1", "l1_value")].into(),
1.0.into(),
),cc @da2ce7