Expire metrics

core/include/prometheus/counter.h

@@ -44,6 +44,7 @@ class Counter {
   ///
   /// Collect is called by the Registry when collecting metrics.
   ClientMetric Collect() const;
+  bool Expired(double) const;
 
  private:
   Gauge gauge_{0.0};

core/include/prometheus/detail/counter_builder.h

@@ -17,12 +17,14 @@ class CounterBuilder {
   CounterBuilder& Labels(const std::map<std::string, std::string>& labels);
   CounterBuilder& Name(const std::string&);
   CounterBuilder& Help(const std::string&);
+  CounterBuilder& Seconds(double);
   Family<Counter>& Register(Registry&);
 
  private:
   std::map<std::string, std::string> labels_;
   std::string name_;
   std::string help_;
+  double seconds_;
 };
 
 }  // namespace detail

core/include/prometheus/detail/gauge_builder.h

@@ -17,12 +17,14 @@ class GaugeBuilder {
   GaugeBuilder& Labels(const std::map<std::string, std::string>& labels);
   GaugeBuilder& Name(const std::string&);
   GaugeBuilder& Help(const std::string&);
+  GaugeBuilder& Seconds(double);
   Family<Gauge>& Register(Registry&);
 
  private:
   std::map<std::string, std::string> labels_;
   std::string name_;
   std::string help_;
+  double seconds_;
 };
 
 }  // namespace detail

core/include/prometheus/detail/histogram_builder.h

@@ -17,12 +17,14 @@ class HistogramBuilder {
   HistogramBuilder& Labels(const std::map<std::string, std::string>& labels);
   HistogramBuilder& Name(const std::string&);
   HistogramBuilder& Help(const std::string&);
+  HistogramBuilder& Seconds(double);
   Family<Histogram>& Register(Registry&);
 
  private:
   std::map<std::string, std::string> labels_;
   std::string name_;
   std::string help_;
+  double seconds_;
 };
 
 }  // namespace detail

core/include/prometheus/detail/summary_builder.h

@@ -17,12 +17,14 @@ class SummaryBuilder {
   SummaryBuilder& Labels(const std::map<std::string, std::string>& labels);
   SummaryBuilder& Name(const std::string&);
   SummaryBuilder& Help(const std::string&);
+  SummaryBuilder& Seconds(double);
   Family<Summary>& Register(Registry&);
 
  private:
   std::map<std::string, std::string> labels_;
   std::string name_;
   std::string help_;
+  double seconds_;
 };
 
 }  // namespace detail

core/include/prometheus/family.h

@@ -88,7 +88,8 @@ class Family : public Collectable {
   /// metric. All these labels are propagated to each time series within the
   /// metric.
   Family(const std::string& name, const std::string& help,
-         const std::map<std::string, std::string>& constant_labels);
+         const std::map<std::string, std::string>& constant_labels,
+         double seconds);
 
   /// \brief Add a new dimensional data.
   ///
@@ -130,15 +131,17 @@ class Family : public Collectable {
   const std::string name_;
   const std::string help_;
   const std::map<std::string, std::string> constant_labels_;
+  double seconds_;
   std::mutex mutex_;
 
   ClientMetric CollectMetric(std::size_t hash, T* metric);
 };
 
 template <typename T>
 Family<T>::Family(const std::string& name, const std::string& help,
-                  const std::map<std::string, std::string>& constant_labels)
-    : name_(name), help_(help), constant_labels_(constant_labels) {
+                  const std::map<std::string, std::string>& constant_labels,
+                  double seconds)
+    : name_(name), help_(help), constant_labels_(constant_labels), seconds_(seconds) {
   assert(CheckMetricName(name_));
 }
 
@@ -196,7 +199,9 @@ std::vector<MetricFamily> Family<T>::Collect() {
   family.help = help_;
   family.type = T::metric_type;
   for (const auto& m : metrics_) {
-    family.metric.push_back(std::move(CollectMetric(m.first, m.second.get())));
+    if (!m.second.get()->Expired(seconds_)) {
+      family.metric.push_back(std::move(CollectMetric(m.first, m.second.get())));
+    }
   }
   return {family};
 }

core/include/prometheus/gauge.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <atomic>
+#include <ctime>
 
 #include "prometheus/client_metric.h"
 #include "prometheus/detail/gauge_builder.h"
@@ -55,10 +56,12 @@ class Gauge {
   ///
   /// Collect is called by the Registry when collecting metrics.
   ClientMetric Collect() const;
+  bool Expired(double) const;
 
  private:
   void Change(double);
   std::atomic<double> value_{0.0};
+  std::atomic<std::time_t> time_{std::time(nullptr)};
 };
 
 /// \brief Return a builder to configure and register a Gauge metric.

core/include/prometheus/histogram.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <vector>
+#include <ctime>
 
 #include "prometheus/client_metric.h"
 #include "prometheus/counter.h"
@@ -55,6 +56,7 @@ class Histogram {
   ///
   /// Collect is called by the Registry when collecting metrics.
   ClientMetric Collect() const;
+  bool Expired(double) const;
 
  private:
   const BucketBoundaries bucket_boundaries_;

core/include/prometheus/registry.h

@@ -52,17 +52,19 @@ class Registry : public Collectable {
 
   template <typename T>
   Family<T>& Add(const std::string& name, const std::string& help,
-                 const std::map<std::string, std::string>& labels);
+                 const std::map<std::string, std::string>& labels,
+                 double seconds);
 
   std::vector<std::unique_ptr<Collectable>> collectables_;
   std::mutex mutex_;
 };
 
 template <typename T>
 Family<T>& Registry::Add(const std::string& name, const std::string& help,
-                         const std::map<std::string, std::string>& labels) {
+                         const std::map<std::string, std::string>& labels,
+                         double seconds) {
   std::lock_guard<std::mutex> lock{mutex_};
-  auto family = detail::make_unique<Family<T>>(name, help, labels);
+  auto family = detail::make_unique<Family<T>>(name, help, labels, seconds);
   auto& ref = *family;
   collectables_.push_back(std::move(family));
   return ref;

core/include/prometheus/summary.h

@@ -81,6 +81,7 @@ class Summary {
   ///
   /// Collect is called by the Registry when collecting metrics.
   ClientMetric Collect();
+  bool Expired(double) const;
 
  private:
   const Quantiles quantiles_;

core/src/counter.cc

@@ -14,6 +14,10 @@ ClientMetric Counter::Collect() const {
   return metric;
 }
 
+bool Counter::Expired(double seconds) const {
+  return false;
+}
+
 detail::CounterBuilder BuildCounter() { return {}; }
 
 }  // namespace prometheus

core/src/detail/counter_builder.cc

@@ -21,8 +21,13 @@ CounterBuilder& CounterBuilder::Help(const std::string& help) {
   return *this;
 }
 
+CounterBuilder& CounterBuilder::Seconds(double seconds) {
+  seconds_ = seconds;
+  return *this;
+}
+
 Family<Counter>& CounterBuilder::Register(Registry& registry) {
-  return registry.Add<Counter>(name_, help_, labels_);
+  return registry.Add<Counter>(name_, help_, labels_, seconds_);
 }
 
 }  // namespace detail

core/src/detail/gauge_builder.cc

@@ -21,8 +21,13 @@ GaugeBuilder& GaugeBuilder::Help(const std::string& help) {
   return *this;
 }
 
+GaugeBuilder& GaugeBuilder::Seconds(double seconds) {
+  seconds_ = seconds;
+  return *this;
+}
+
 Family<Gauge>& GaugeBuilder::Register(Registry& registry) {
-  return registry.Add<Gauge>(name_, help_, labels_);
+  return registry.Add<Gauge>(name_, help_, labels_, seconds_);
 }
 
 }  // namespace detail

core/src/detail/histogram_builder.cc

@@ -21,8 +21,13 @@ HistogramBuilder& HistogramBuilder::Help(const std::string& help) {
   return *this;
 }
 
+HistogramBuilder& HistogramBuilder::Seconds(double seconds) {
+  seconds_ = seconds;
+  return *this;
+}
+
 Family<Histogram>& HistogramBuilder::Register(Registry& registry) {
-  return registry.Add<Histogram>(name_, help_, labels_);
+  return registry.Add<Histogram>(name_, help_, labels_, seconds_);
 }
 
 }  // namespace detail

core/src/detail/summary_builder.cc

@@ -21,8 +21,13 @@ SummaryBuilder& SummaryBuilder::Help(const std::string& help) {
   return *this;
 }
 
+SummaryBuilder& SummaryBuilder::Seconds(double seconds) {
+  seconds_ = seconds;
+  return *this;
+}
+
 Family<Summary>& SummaryBuilder::Register(Registry& registry) {
-  return registry.Add<Summary>(name_, help_, labels_);
+  return registry.Add<Summary>(name_, help_, labels_, seconds_);
 }
 
 }  // namespace detail

core/src/gauge.cc

@@ -24,12 +24,16 @@ void Gauge::Decrement(const double value) {
   Change(-1.0 * value);
 }
 
-void Gauge::Set(const double value) { value_.store(value); }
+void Gauge::Set(const double value) {
+  value_.store(value);
+  time_.store(std::time(nullptr));
+}
 
 void Gauge::Change(const double value) {
   auto current = value_.load();
   while (!value_.compare_exchange_weak(current, current + value))
     ;
+  time_.store(std::time(nullptr));
 }
 
 void Gauge::SetToCurrentTime() {
@@ -45,6 +49,11 @@ ClientMetric Gauge::Collect() const {
   return metric;
 }
 
+bool Gauge::Expired(double seconds) const {
+  const auto time = std::time(nullptr);
+  return std::difftime(time, time_) > seconds;
+}
+
 detail::GaugeBuilder BuildGauge() { return {}; }
 
 }  // namespace prometheus

core/src/histogram.cc

@@ -43,6 +43,10 @@ ClientMetric Histogram::Collect() const {
   return metric;
 }
 
+bool Histogram::Expired(double seconds) const {
+  return false;
+}
+
 detail::HistogramBuilder BuildHistogram() { return {}; }
 
 }  // namespace prometheus

core/src/summary.cc

@@ -34,6 +34,10 @@ ClientMetric Summary::Collect() {
   return metric;
 }
 
+bool Summary::Expired(double seconds) const {
+  return false;
+}
+
 detail::SummaryBuilder BuildSummary() { return {}; }
 
 }  // namespace prometheus