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Add units to prometheus metric lines #535

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Nov 25, 2024
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16 changes: 16 additions & 0 deletions metrics-exporter-prometheus/src/exporter/builder.rs
Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,7 @@ pub struct PrometheusBuilder {
upkeep_timeout: Duration,
recency_mask: MetricKindMask,
global_labels: Option<IndexMap<String, String>>,
enable_unit_suffix: bool,
}

impl PrometheusBuilder {
Expand Down Expand Up @@ -80,6 +81,7 @@ impl PrometheusBuilder {
upkeep_timeout,
recency_mask: MetricKindMask::NONE,
global_labels: None,
enable_unit_suffix: false,
}
}

Expand Down Expand Up @@ -283,6 +285,19 @@ impl PrometheusBuilder {
Ok(self)
}

/// Sets whether a unit suffix is appended to metric names.
///
/// When this is enabled and the [`Unit`][metrics::Unit] of metric is
/// given, then the exported metric name will be appended to according to
/// the [Prometheus Best Practices](https://prometheus.io/docs/practices/naming/).
///
/// Defaults to false.
#[must_use]
pub fn set_enable_unit_suffix(mut self, enabled: bool) -> Self {
self.enable_unit_suffix = enabled;
self
}

/// Sets the bucket for a specific pattern.
///
/// The match pattern can be a full match (equality), prefix match, or suffix match. The
Expand Down Expand Up @@ -513,6 +528,7 @@ impl PrometheusBuilder {
),
descriptions: RwLock::new(HashMap::new()),
global_labels: self.global_labels.unwrap_or_default(),
enable_unit_suffix: self.enable_unit_suffix,
};

PrometheusRecorder::from(inner)
Expand Down
15 changes: 14 additions & 1 deletion metrics-exporter-prometheus/src/formatting.rs
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
//! Helpers for rendering metrics in the Prometheus exposition format.

use indexmap::IndexMap;
use metrics::Key;
use metrics::{Key, Unit};

/// Breaks a key into the name and label components, with optional default labels.
///
Expand Down Expand Up @@ -64,6 +64,7 @@ pub fn write_metric_line<T, T2>(
labels: &[String],
additional_label: Option<(&'static str, T)>,
value: T2,
unit: Option<Unit>,
) where
T: std::fmt::Display,
T2: std::fmt::Display,
Expand All @@ -74,6 +75,18 @@ pub fn write_metric_line<T, T2>(
buffer.push_str(suffix);
}

match unit {
Some(Unit::Count) | None => {}
Some(Unit::Percent) => {
buffer.push('_');
buffer.push_str("ratio");
}
Some(unit) => {
buffer.push('_');
buffer.push_str(unit.as_str());
}
}

if !labels.is_empty() || additional_label.is_some() {
buffer.push('{');

Expand Down
78 changes: 55 additions & 23 deletions metrics-exporter-prometheus/src/recorder.rs
Original file line number Diff line number Diff line change
Expand Up @@ -21,8 +21,9 @@ pub(crate) struct Inner {
pub recency: Recency<Key>,
pub distributions: RwLock<HashMap<String, IndexMap<Vec<String>, Distribution>>>,
pub distribution_builder: DistributionBuilder,
pub descriptions: RwLock<HashMap<String, SharedString>>,
pub descriptions: RwLock<HashMap<String, (SharedString, Option<Unit>)>>,
pub global_labels: IndexMap<String, String>,
pub enable_unit_suffix: bool,
}

impl Inner {
Expand Down Expand Up @@ -116,33 +117,52 @@ impl Inner {
let descriptions = self.descriptions.read().unwrap_or_else(PoisonError::into_inner);

for (name, mut by_labels) in counters.drain() {
if let Some(desc) = descriptions.get(name.as_str()) {
let unit = descriptions.get(name.as_str()).and_then(|(desc, unit)| {
write_help_line(&mut output, name.as_str(), desc);
}
*unit
});

write_type_line(&mut output, name.as_str(), "counter");
for (labels, value) in by_labels.drain() {
write_metric_line::<&str, u64>(&mut output, &name, None, &labels, None, value);
write_metric_line::<&str, u64>(
&mut output,
&name,
None,
&labels,
None,
value,
unit.filter(|_| self.enable_unit_suffix),
);
}
output.push('\n');
}

for (name, mut by_labels) in gauges.drain() {
if let Some(desc) = descriptions.get(name.as_str()) {
let unit = descriptions.get(name.as_str()).and_then(|(desc, unit)| {
write_help_line(&mut output, name.as_str(), desc);
}
*unit
});

write_type_line(&mut output, name.as_str(), "gauge");
for (labels, value) in by_labels.drain() {
write_metric_line::<&str, f64>(&mut output, &name, None, &labels, None, value);
write_metric_line::<&str, f64>(
&mut output,
&name,
None,
&labels,
None,
value,
unit.filter(|_| self.enable_unit_suffix),
);
}
output.push('\n');
}

for (name, mut by_labels) in distributions.drain() {
if let Some(desc) = descriptions.get(name.as_str()) {
let unit = descriptions.get(name.as_str()).and_then(|(desc, unit)| {
write_help_line(&mut output, name.as_str(), desc);
}
*unit
});

let distribution_type = self.distribution_builder.get_distribution_type(name.as_str());
write_type_line(&mut output, name.as_str(), distribution_type);
Expand All @@ -159,6 +179,7 @@ impl Inner {
&labels,
Some(("quantile", quantile.value())),
value,
unit.filter(|_| self.enable_unit_suffix),
);
}

Expand All @@ -173,6 +194,7 @@ impl Inner {
&labels,
Some(("le", le)),
count,
unit.filter(|_| self.enable_unit_suffix),
);
}
write_metric_line(
Expand All @@ -182,20 +204,30 @@ impl Inner {
&labels,
Some(("le", "+Inf")),
histogram.count(),
unit.filter(|_| self.enable_unit_suffix),
);

(histogram.sum(), histogram.count())
}
};

write_metric_line::<&str, f64>(&mut output, &name, Some("sum"), &labels, None, sum);
write_metric_line::<&str, f64>(
&mut output,
&name,
Some("sum"),
&labels,
None,
sum,
unit,
);
write_metric_line::<&str, u64>(
&mut output,
&name,
Some("count"),
&labels,
None,
count,
unit,
);
}

Expand Down Expand Up @@ -226,11 +258,16 @@ impl PrometheusRecorder {
PrometheusHandle { inner: self.inner.clone() }
}

fn add_description_if_missing(&self, key_name: &KeyName, description: SharedString) {
fn add_description_if_missing(
&self,
key_name: &KeyName,
description: SharedString,
unit: Option<Unit>,
) {
let sanitized = sanitize_metric_name(key_name.as_str());
let mut descriptions =
self.inner.descriptions.write().unwrap_or_else(PoisonError::into_inner);
descriptions.entry(sanitized).or_insert(description);
descriptions.entry(sanitized).or_insert((description, unit));
}
}

Expand All @@ -241,21 +278,16 @@ impl From<Inner> for PrometheusRecorder {
}

impl Recorder for PrometheusRecorder {
fn describe_counter(&self, key_name: KeyName, _unit: Option<Unit>, description: SharedString) {
self.add_description_if_missing(&key_name, description);
fn describe_counter(&self, key_name: KeyName, unit: Option<Unit>, description: SharedString) {
self.add_description_if_missing(&key_name, description, unit);
}

fn describe_gauge(&self, key_name: KeyName, _unit: Option<Unit>, description: SharedString) {
self.add_description_if_missing(&key_name, description);
fn describe_gauge(&self, key_name: KeyName, unit: Option<Unit>, description: SharedString) {
self.add_description_if_missing(&key_name, description, unit);
}

fn describe_histogram(
&self,
key_name: KeyName,
_unit: Option<Unit>,
description: SharedString,
) {
self.add_description_if_missing(&key_name, description);
fn describe_histogram(&self, key_name: KeyName, unit: Option<Unit>, description: SharedString) {
self.add_description_if_missing(&key_name, description, unit);
}

fn register_counter(&self, key: &Key, _metadata: &Metadata<'_>) -> Counter {
Expand Down
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