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Sep 24, 2025
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refactor how collected metrics are stored to avoid parsing labels #605

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39 changes: 36 additions & 3 deletions metrics-exporter-prometheus/src/common.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -80,9 +80,42 @@ pub enum BuildError {
ZeroBucketDuration,
}

/// Represents a set of labels as structured key-value pairs
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct LabelSet {
pub labels: Vec<(String, String)>,
}

impl LabelSet {
pub fn from_key_and_global(
key: &metrics::Key,
global_labels: &IndexMap<String, String>,
) -> Self {
let mut labels = global_labels.clone();
key.labels().for_each(|label| {
labels.insert(label.key().to_string(), label.value().to_string());
});
Self { labels: labels.into_iter().collect() }
}

pub fn is_empty(&self) -> bool {
self.labels.is_empty()
}

pub fn to_strings(&self) -> impl Iterator<Item = String> + '_ {
self.labels.iter().map(|(k, v)| {
format!(
"{}=\"{}\"",
crate::formatting::sanitize_label_key(k),
crate::formatting::sanitize_label_value(v)
)
})
}
}

#[derive(Debug)]
pub struct Snapshot {
pub counters: HashMap<String, HashMap<Vec<String>, u64>>,
pub gauges: HashMap<String, HashMap<Vec<String>, f64>>,
pub distributions: HashMap<String, IndexMap<Vec<String>, Distribution>>,
pub counters: HashMap<String, HashMap<LabelSet, u64>>,
pub gauges: HashMap<String, HashMap<LabelSet, f64>>,
pub distributions: HashMap<String, IndexMap<LabelSet, Distribution>>,
}
32 changes: 5 additions & 27 deletions metrics-exporter-prometheus/src/formatting.rs
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Original file line number Diff line number Diff line change
@@ -1,30 +1,8 @@
//! Helpers for rendering metrics in the Prometheus exposition format.

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

/// Breaks a key into the name and label components, with optional default labels.
///
/// If any of the default labels are not already present, they will be added to the overall list of labels.
///
/// Both the metric name, and labels, are sanitized. See [`sanitize_metric_name`], [`sanitize_label_key`],
/// and [`sanitize_label_value`] for more information.
pub fn key_to_parts(
key: &Key,
default_labels: Option<&IndexMap<String, String>>,
) -> (String, Vec<String>) {
let name = sanitize_metric_name(key.name());
let mut values = default_labels.cloned().unwrap_or_default();
key.labels().for_each(|label| {
values.insert(label.key().to_string(), label.value().to_string());
});
let labels = values
.iter()
.map(|(k, v)| format!("{}=\"{}\"", sanitize_label_key(k), sanitize_label_value(v)))
.collect();

(name, labels)
}
use crate::common::LabelSet;

/// Writes a help (description) line in the Prometheus [exposition format].
///
Expand Down Expand Up @@ -73,7 +51,7 @@ pub fn write_metric_line<T, T2>(
buffer: &mut String,
name: &str,
suffix: Option<&'static str>,
labels: &[String],
labels: &LabelSet,
additional_label: Option<(&'static str, T)>,
value: T2,
unit: Option<Unit>,
Expand All @@ -87,13 +65,13 @@ pub fn write_metric_line<T, T2>(
buffer.push('{');

let mut first = true;
for label in labels {
for label in labels.to_strings() {
if first {
first = false;
} else {
buffer.push(',');
}
buffer.push_str(label);
buffer.push_str(&label);
}

if let Some((name, value)) = additional_label {
Expand Down
83 changes: 35 additions & 48 deletions metrics-exporter-prometheus/src/protobuf.rs
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Original file line number Diff line number Diff line change
@@ -1,11 +1,10 @@
//! Protobuf serialization support for Prometheus metrics.

use indexmap::IndexMap;
use metrics::Unit;
use prost::Message;
use std::collections::HashMap;

use crate::common::Snapshot;
use crate::common::{LabelSet, Snapshot};
use crate::distribution::Distribution;
use crate::formatting::sanitize_metric_name;

Expand All @@ -26,28 +25,27 @@ pub(crate) const PROTOBUF_CONTENT_TYPE: &str =
/// length header.
#[allow(clippy::too_many_lines)]
pub(crate) fn render_protobuf(
snapshot: &Snapshot,
snapshot: Snapshot,
descriptions: &HashMap<String, (metrics::SharedString, Option<Unit>)>,
global_labels: &IndexMap<String, String>,
counter_suffix: Option<&'static str>,
) -> Vec<u8> {
let mut output = Vec::new();

// Process counters
for (name, by_labels) in &snapshot.counters {
let sanitized_name = sanitize_metric_name(name);
for (name, by_labels) in snapshot.counters {
let sanitized_name = sanitize_metric_name(&name);
let help =
descriptions.get(name.as_str()).map(|(desc, _)| desc.to_string()).unwrap_or_default();

let mut metrics = Vec::new();
for (labels, value) in by_labels {
let label_pairs = parse_labels(labels, global_labels);
let label_pairs = label_set_to_protobuf(labels);

metrics.push(pb::Metric {
label: label_pairs,
counter: Some(pb::Counter {
#[allow(clippy::cast_precision_loss)]
value: Some(*value as f64),
value: Some(value as f64),

..Default::default()
}),
Expand All @@ -68,18 +66,18 @@ pub(crate) fn render_protobuf(
}

// Process gauges
for (name, by_labels) in &snapshot.gauges {
let sanitized_name = sanitize_metric_name(name);
for (name, by_labels) in snapshot.gauges {
let sanitized_name = sanitize_metric_name(&name);
let help =
descriptions.get(name.as_str()).map(|(desc, _)| desc.to_string()).unwrap_or_default();

let mut metrics = Vec::new();
for (labels, value) in by_labels {
let label_pairs = parse_labels(labels, global_labels);
let label_pairs = label_set_to_protobuf(labels);

metrics.push(pb::Metric {
label: label_pairs,
gauge: Some(pb::Gauge { value: Some(*value) }),
gauge: Some(pb::Gauge { value: Some(value) }),

..Default::default()
});
Expand All @@ -97,18 +95,20 @@ pub(crate) fn render_protobuf(
}

// Process distributions (histograms and summaries)
for (name, by_labels) in &snapshot.distributions {
let sanitized_name = sanitize_metric_name(name);
for (name, by_labels) in snapshot.distributions {
let sanitized_name = sanitize_metric_name(&name);
let help =
descriptions.get(name.as_str()).map(|(desc, _)| desc.to_string()).unwrap_or_default();

let mut metrics = Vec::new();
let mut metric_type = None;
for (labels, distribution) in by_labels {
let label_pairs = parse_labels(labels, global_labels);
let label_pairs = label_set_to_protobuf(labels);

let metric = match distribution {
Distribution::Summary(summary, quantiles, sum) => {
use quanta::Instant;
metric_type = Some(pb::MetricType::Summary);
let snapshot = summary.snapshot(Instant::now());
let quantile_values: Vec<pb::Quantile> = quantiles
.iter()
Expand All @@ -122,7 +122,7 @@ pub(crate) fn render_protobuf(
label: label_pairs,
summary: Some(pb::Summary {
sample_count: Some(summary.count() as u64),
sample_sum: Some(*sum),
sample_sum: Some(sum),
quantile: quantile_values,

created_timestamp: None,
Expand All @@ -132,6 +132,7 @@ pub(crate) fn render_protobuf(
}
}
Distribution::Histogram(histogram) => {
metric_type = Some(pb::MetricType::Histogram);
let mut buckets = Vec::new();
for (le, count) in histogram.buckets() {
buckets.push(pb::Bucket {
Expand Down Expand Up @@ -167,10 +168,9 @@ pub(crate) fn render_protobuf(
metrics.push(metric);
}

let metric_type = match by_labels.values().next() {
Some(Distribution::Summary(_, _, _)) => pb::MetricType::Summary,
Some(Distribution::Histogram(_)) => pb::MetricType::Histogram,
None => continue, // Skip empty metric families
let Some(metric_type) = metric_type else {
// Skip empty metric families
continue;
};

let metric_family = pb::MetricFamily {
Expand All @@ -187,29 +187,11 @@ pub(crate) fn render_protobuf(
output
}

fn parse_labels(labels: &[String], global_labels: &IndexMap<String, String>) -> Vec<pb::LabelPair> {
fn label_set_to_protobuf(labels: LabelSet) -> Vec<pb::LabelPair> {
let mut label_pairs = Vec::new();

// Add global labels first
for (key, value) in global_labels {
label_pairs.push(pb::LabelPair { name: Some(key.clone()), value: Some(value.clone()) });
}

// Add metric-specific labels
for label_str in labels {
if let Some(eq_pos) = label_str.find('=') {
let key = &label_str[..eq_pos];
let value = &label_str[eq_pos + 1..];
let value = value.trim_matches('"');

// Skip if this label key already exists from global labels
if !global_labels.contains_key(key) {
label_pairs.push(pb::LabelPair {
name: Some(key.to_string()),
value: Some(value.to_string()),
});
}
}
for (key, value) in labels.labels {
label_pairs.push(pb::LabelPair { name: Some(key), value: Some(value) });
}

label_pairs
Expand All @@ -235,16 +217,18 @@ mod tests {
fn test_render_protobuf_counters() {
let mut counters = HashMap::new();
let mut counter_labels = HashMap::new();
counter_labels.insert(vec!["method=\"GET\"".to_string()], 42u64);
let labels = LabelSet::from_key_and_global(
&metrics::Key::from_parts("", vec![metrics::Label::new("method", "GET")]),
&IndexMap::new(),
);
counter_labels.insert(labels, 42u64);
counters.insert("http_requests".to_string(), counter_labels);

let snapshot = Snapshot { counters, gauges: HashMap::new(), distributions: HashMap::new() };

let descriptions = HashMap::new();
let global_labels = IndexMap::new();

let protobuf_data =
render_protobuf(&snapshot, &descriptions, &global_labels, Some("total"));
let protobuf_data = render_protobuf(snapshot, &descriptions, Some("total"));

assert!(!protobuf_data.is_empty(), "Protobuf data should not be empty");

Expand All @@ -264,7 +248,11 @@ mod tests {
fn test_render_protobuf_gauges() {
let mut gauges = HashMap::new();
let mut gauge_labels = HashMap::new();
gauge_labels.insert(vec!["instance=\"localhost\"".to_string()], 0.75f64);
let labels = LabelSet::from_key_and_global(
&metrics::Key::from_parts("", vec![metrics::Label::new("instance", "localhost")]),
&IndexMap::new(),
);
gauge_labels.insert(labels, 0.75f64);
gauges.insert("cpu_usage".to_string(), gauge_labels);

let snapshot = Snapshot { counters: HashMap::new(), gauges, distributions: HashMap::new() };
Expand All @@ -274,9 +262,8 @@ mod tests {
"cpu_usage".to_string(),
(SharedString::const_str("CPU usage percentage"), None),
);
let global_labels = IndexMap::new();

let protobuf_data = render_protobuf(&snapshot, &descriptions, &global_labels, None);
let protobuf_data = render_protobuf(snapshot, &descriptions, None);

assert!(!protobuf_data.is_empty(), "Protobuf data should not be empty");

Expand Down
25 changes: 12 additions & 13 deletions metrics-exporter-prometheus/src/recorder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,18 +8,18 @@ use metrics::{Counter, Gauge, Histogram, Key, KeyName, Metadata, Recorder, Share
use metrics_util::registry::{Recency, Registry};
use quanta::Instant;

use crate::common::Snapshot;
use crate::common::{LabelSet, Snapshot};
use crate::distribution::{Distribution, DistributionBuilder};
use crate::formatting::{
key_to_parts, sanitize_metric_name, write_help_line, write_metric_line, write_type_line,
sanitize_metric_name, write_help_line, write_metric_line, write_type_line,
};
use crate::registry::GenerationalAtomicStorage;

#[derive(Debug)]
pub(crate) struct Inner {
pub registry: Registry<Key, GenerationalAtomicStorage>,
pub recency: Recency<Key>,
pub distributions: RwLock<HashMap<String, IndexMap<Vec<String>, Distribution>>>,
pub distributions: RwLock<HashMap<String, IndexMap<LabelSet, Distribution>>>,
pub distribution_builder: DistributionBuilder,
pub descriptions: RwLock<HashMap<String, (SharedString, Option<Unit>)>>,
pub global_labels: IndexMap<String, String>,
Expand All @@ -37,7 +37,8 @@ impl Inner {
continue;
}

let (name, labels) = key_to_parts(&key, Some(&self.global_labels));
let name = sanitize_metric_name(key.name());
let labels = LabelSet::from_key_and_global(&key, &self.global_labels);
let value = counter.get_inner().load(Ordering::Acquire);
let entry =
counters.entry(name).or_insert_with(HashMap::new).entry(labels).or_insert(0);
Expand All @@ -52,7 +53,8 @@ impl Inner {
continue;
}

let (name, labels) = key_to_parts(&key, Some(&self.global_labels));
let name = sanitize_metric_name(key.name());
let labels = LabelSet::from_key_and_global(&key, &self.global_labels);
let value = f64::from_bits(gauge.get_inner().load(Ordering::Acquire));
let entry =
gauges.entry(name).or_insert_with(HashMap::new).entry(labels).or_insert(0.0);
Expand All @@ -69,7 +71,8 @@ impl Inner {
// Since we store aggregated distributions directly, when we're told that a metric
// is not recent enough and should be/was deleted from the registry, we also need to
// delete it on our side as well.
let (name, labels) = key_to_parts(&key, Some(&self.global_labels));
let name = sanitize_metric_name(key.name());
let labels = LabelSet::from_key_and_global(&key, &self.global_labels);
let mut wg = self.distributions.write().unwrap_or_else(PoisonError::into_inner);
let delete_by_name = if let Some(by_name) = wg.get_mut(&name) {
by_name.swap_remove(&labels);
Expand Down Expand Up @@ -98,7 +101,8 @@ impl Inner {
fn drain_histograms_to_distributions(&self) {
let histogram_handles = self.registry.get_histogram_handles();
for (key, histogram) in histogram_handles {
let (name, labels) = key_to_parts(&key, Some(&self.global_labels));
let name = sanitize_metric_name(key.name());
let labels = LabelSet::from_key_and_global(&key, &self.global_labels);

let mut wg = self.distributions.write().unwrap_or_else(PoisonError::into_inner);
let entry = wg
Expand Down Expand Up @@ -332,12 +336,7 @@ impl PrometheusHandle {
let snapshot = self.inner.get_recent_metrics();
let descriptions = self.inner.descriptions.read().unwrap_or_else(PoisonError::into_inner);

crate::protobuf::render_protobuf(
&snapshot,
&descriptions,
&self.inner.global_labels,
self.inner.counter_suffix,
)
crate::protobuf::render_protobuf(snapshot, &descriptions, self.inner.counter_suffix)
}

/// Performs upkeeping operations to ensure metrics held by recorder are up-to-date and do not
Expand Down