chore(core): Introduce Labels type

core/benchmarks/benchmark_helpers.cc

@@ -2,6 +2,7 @@
 
 #include <algorithm>
 #include <cstdlib>
+#include <map>
 
 std::string GenerateRandomString(std::size_t length) {
   auto randchar = []() -> char {
@@ -14,10 +15,9 @@ std::string GenerateRandomString(std::size_t length) {
   return str;
 }
 
-std::map<std::string, std::string> GenerateRandomLabels(
-    std::size_t number_of_pairs) {
+prometheus::Labels GenerateRandomLabels(std::size_t number_of_pairs) {
   const auto label_character_count = 10;
-  auto label_pairs = std::map<std::string, std::string>{};
+  auto label_pairs = prometheus::Labels{};
   for (std::size_t i = 0; i < number_of_pairs; i++) {
     label_pairs.insert({GenerateRandomString(label_character_count),
                         GenerateRandomString(label_character_count)});

core/benchmarks/benchmark_helpers.h

@@ -1,9 +1,9 @@
 #pragma once
 
 #include <cstddef>
-#include <map>
 #include <string>
 
+#include "prometheus/labels.h"
+
 std::string GenerateRandomString(std::size_t length);
-std::map<std::string, std::string> GenerateRandomLabels(
-    std::size_t number_of_labels);
+prometheus::Labels GenerateRandomLabels(std::size_t number_of_labels);

core/benchmarks/counter_bench.cc

@@ -1,7 +1,5 @@
 #include <benchmark/benchmark.h>
 
-#include <string>
-
 #include "prometheus/counter.h"
 #include "prometheus/family.h"
 #include "prometheus/registry.h"

core/benchmarks/gauge_bench.cc

@@ -1,7 +1,5 @@
 #include <benchmark/benchmark.h>
 
-#include <string>
-
 #include "prometheus/family.h"
 #include "prometheus/gauge.h"
 #include "prometheus/registry.h"

core/benchmarks/histogram_bench.cc

@@ -3,7 +3,6 @@
 #include <chrono>
 #include <cstdint>
 #include <random>
-#include <string>
 #include <vector>
 
 #include "prometheus/family.h"

core/benchmarks/summary_bench.cc

@@ -4,7 +4,6 @@
 #include <chrono>
 #include <cmath>
 #include <random>
-#include <string>
 #include <vector>
 
 #include "prometheus/family.h"

core/include/prometheus/counter.h

@@ -72,7 +72,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Counter {
 ///
 /// - Name(const std::string&) to set the metric name,
 /// - Help(const std::string&) to set an additional description.
-/// - Label(const std::map<std::string, std::string>&) to assign a set of
+/// - Labels(const Labels&) to assign a set of
 ///   key-value pairs (= labels) to the metric.
 ///
 /// To finish the configuration of the Counter metric, register it with

core/include/prometheus/detail/builder.h

@@ -1,8 +1,9 @@
 #pragma once
 
-#include <map>
 #include <string>
 
+#include "prometheus/labels.h"
+
 // IWYU pragma: private
 // IWYU pragma: no_include "prometheus/family.h"
 
@@ -17,13 +18,13 @@ namespace detail {
 template <typename T>
 class Builder {
  public:
-  Builder& Labels(const std::map<std::string, std::string>& labels);
+  Builder& Labels(const ::prometheus::Labels& labels);
   Builder& Name(const std::string&);
   Builder& Help(const std::string&);
   Family<T>& Register(Registry&);
 
  private:
-  std::map<std::string, std::string> labels_;
+  ::prometheus::Labels labels_;
   std::string name_;
   std::string help_;
 };

core/include/prometheus/detail/utils.h

@@ -1,10 +1,9 @@
 #pragma once
 
 #include <cstddef>
-#include <map>
-#include <string>
 
 #include "prometheus/detail/core_export.h"
+#include "prometheus/labels.h"
 
 namespace prometheus {
 namespace detail {
@@ -16,8 +15,7 @@ struct PROMETHEUS_CPP_CORE_EXPORT LabelHasher {
   /// \param labels The map that will be computed the hash value.
   ///
   /// \returns The hash value of the given labels.
-  std::size_t operator()(
-      const std::map<std::string, std::string>& labels) const;
+  std::size_t operator()(const Labels& labels) const;
 };
 
 }  // namespace detail

core/include/prometheus/family.h

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <map>
 #include <memory>
 #include <mutex>
 #include <string>
@@ -12,6 +11,7 @@
 #include "prometheus/detail/core_export.h"
 #include "prometheus/detail/future_std.h"
 #include "prometheus/detail/utils.h"
+#include "prometheus/labels.h"
 #include "prometheus/metric_family.h"
 
 // IWYU pragma: no_include "prometheus/counter.h"
@@ -89,7 +89,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   /// metric.
   /// \throw std::runtime_exception on invalid metric or label names.
   Family(const std::string& name, const std::string& help,
-         const std::map<std::string, std::string>& constant_labels);
+         const Labels& constant_labels);
 
   /// \brief Add a new dimensional data.
   ///
@@ -109,7 +109,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   /// labels already exists - the already existing dimensional data.
   /// \throw std::runtime_exception on invalid label names.
   template <typename... Args>
-  T& Add(const std::map<std::string, std::string>& labels, Args&&... args) {
+  T& Add(const Labels& labels, Args&&... args) {
     return Add(labels, detail::make_unique<T>(args...));
   }
 
@@ -122,7 +122,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   /// \brief Returns true if the dimensional data with the given labels exist
   ///
   /// \param labels A set of key-value pairs (= labels) of the dimensional data.
-  bool Has(const std::map<std::string, std::string>& labels) const;
+  bool Has(const Labels& labels) const;
 
   /// \brief Returns the name for this family.
   ///
@@ -132,7 +132,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   /// \brief Returns the constant labels for this family.
   ///
   /// \return All constant labels as key-value pairs.
-  const std::map<std::string, std::string> GetConstantLabels() const;
+  const Labels GetConstantLabels() const;
 
   /// \brief Returns the current value of each dimensional data.
   ///
@@ -142,19 +142,15 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   std::vector<MetricFamily> Collect() const override;
 
  private:
-  std::unordered_map<std::map<std::string, std::string>, std::unique_ptr<T>,
-                     detail::LabelHasher>
-      metrics_;
+  std::unordered_map<Labels, std::unique_ptr<T>, detail::LabelHasher> metrics_;
 
   const std::string name_;
   const std::string help_;
-  const std::map<std::string, std::string> constant_labels_;
+  const Labels constant_labels_;
   mutable std::mutex mutex_;
 
-  ClientMetric CollectMetric(const std::map<std::string, std::string>& labels,
-                             T* metric) const;
-  T& Add(const std::map<std::string, std::string>& labels,
-         std::unique_ptr<T> object);
+  ClientMetric CollectMetric(const Labels& labels, T* metric) const;
+  T& Add(const Labels& labels, std::unique_ptr<T> object);
 };
 
 }  // namespace prometheus

core/include/prometheus/gauge.h

@@ -84,7 +84,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Gauge {
 ///
 /// - Name(const std::string&) to set the metric name,
 /// - Help(const std::string&) to set an additional description.
-/// - Label(const std::map<std::string, std::string>&) to assign a set of
+/// - Labels(const Labels&) to assign a set of
 ///   key-value pairs (= labels) to the metric.
 ///
 /// To finish the configuration of the Gauge metric register it with

core/include/prometheus/histogram.h

@@ -96,7 +96,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Histogram {
 ///
 /// - Name(const std::string&) to set the metric name,
 /// - Help(const std::string&) to set an additional description.
-/// - Label(const std::map<std::string, std::string>&) to assign a set of
+/// - Labels(const Labels&) to assign a set of
 ///   key-value pairs (= labels) to the metric.
 ///
 /// To finish the configuration of the Histogram metric register it with

core/include/prometheus/labels.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <map>
+#include <string>
+
+namespace prometheus {
+
+/// \brief Multiple labels and their value.
+using Labels = std::map<std::string, std::string>;
+
+}  // namespace prometheus

core/include/prometheus/registry.h

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <map>
 #include <memory>
 #include <mutex>
 #include <string>
@@ -9,6 +8,7 @@
 #include "prometheus/collectable.h"
 #include "prometheus/detail/core_export.h"
 #include "prometheus/family.h"
+#include "prometheus/labels.h"
 #include "prometheus/metric_family.h"
 
 namespace prometheus {
@@ -96,7 +96,7 @@ class PROMETHEUS_CPP_CORE_EXPORT 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 Labels& labels);
 
   const InsertBehavior insert_behavior_;
   std::vector<std::unique_ptr<Family<Counter>>> counters_;

core/include/prometheus/summary.h

@@ -113,7 +113,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Summary {
 ///
 /// - Name(const std::string&) to set the metric name,
 /// - Help(const std::string&) to set an additional description.
-/// - Label(const std::map<std::string, std::string>&) to assign a set of
+/// - Labels(const Labels&) to assign a set of
 ///   key-value pairs (= labels) to the metric.
 ///
 /// To finish the configuration of the Summary metric register it with

core/src/detail/builder.cc

@@ -12,8 +12,7 @@ namespace prometheus {
 namespace detail {
 
 template <typename T>
-Builder<T>& Builder<T>::Labels(
-    const std::map<std::string, std::string>& labels) {
+Builder<T>& Builder<T>::Labels(const ::prometheus::Labels& labels) {
   labels_ = labels;
   return *this;
 }

core/src/detail/utils.cc

@@ -1,5 +1,6 @@
 #include "prometheus/detail/utils.h"
 
+#include <map>
 #include <utility>
 
 #include "hash.h"
@@ -8,8 +9,7 @@ namespace prometheus {
 
 namespace detail {
 
-std::size_t LabelHasher::operator()(
-    const std::map<std::string, std::string>& labels) const {
+std::size_t LabelHasher::operator()(const Labels& labels) const {
   size_t seed = 0;
   for (auto& label : labels) {
     hash_combine(&seed, label.first, label.second);

core/src/family.cc

@@ -2,6 +2,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <map>
 #include <stdexcept>
 #include <type_traits>
 #include <utility>
@@ -16,7 +17,7 @@ namespace prometheus {
 
 template <typename T>
 Family<T>::Family(const std::string& name, const std::string& help,
-                  const std::map<std::string, std::string>& constant_labels)
+                  const Labels& constant_labels)
     : name_(name), help_(help), constant_labels_(constant_labels) {
   if (!CheckMetricName(name_)) {
     throw std::invalid_argument("Invalid metric name");
@@ -30,8 +31,7 @@ Family<T>::Family(const std::string& name, const std::string& help,
 }
 
 template <typename T>
-T& Family<T>::Add(const std::map<std::string, std::string>& labels,
-                  std::unique_ptr<T> object) {
+T& Family<T>::Add(const Labels& labels, std::unique_ptr<T> object) {
   std::lock_guard<std::mutex> lock{mutex_};
 
   auto insert_result =
@@ -70,7 +70,7 @@ void Family<T>::Remove(T* metric) {
 }
 
 template <typename T>
-bool Family<T>::Has(const std::map<std::string, std::string>& labels) const {
+bool Family<T>::Has(const Labels& labels) const {
   std::lock_guard<std::mutex> lock{mutex_};
   return metrics_.count(labels) != 0u;
 }
@@ -81,7 +81,7 @@ const std::string& Family<T>::GetName() const {
 }
 
 template <typename T>
-const std::map<std::string, std::string> Family<T>::GetConstantLabels() const {
+const Labels Family<T>::GetConstantLabels() const {
   return constant_labels_;
 }
 
@@ -105,8 +105,8 @@ std::vector<MetricFamily> Family<T>::Collect() const {
 }
 
 template <typename T>
-ClientMetric Family<T>::CollectMetric(
-    const std::map<std::string, std::string>& metric_labels, T* metric) const {
+ClientMetric Family<T>::CollectMetric(const Labels& metric_labels,
+                                      T* metric) const {
   auto collected = metric->Collect();
   collected.label.reserve(constant_labels_.size() + metric_labels.size());
   const auto add_label =

core/src/registry.cc

@@ -96,7 +96,7 @@ bool Registry::NameExistsInOtherType<Summary>(const std::string& name) const {
 
 template <typename T>
 Family<T>& Registry::Add(const std::string& name, const std::string& help,
-                         const std::map<std::string, std::string>& labels) {
+                         const Labels& labels) {
   std::lock_guard<std::mutex> lock{mutex_};
 
   if (NameExistsInOtherType<T>(name)) {
@@ -137,20 +137,20 @@ Family<T>& Registry::Add(const std::string& name, const std::string& help,
   return ref;
 }
 
-template Family<Counter>& Registry::Add(
-    const std::string& name, const std::string& help,
-    const std::map<std::string, std::string>& labels);
+template Family<Counter>& Registry::Add(const std::string& name,
+                                        const std::string& help,
+                                        const Labels& labels);
 
-template Family<Gauge>& Registry::Add(
-    const std::string& name, const std::string& help,
-    const std::map<std::string, std::string>& labels);
+template Family<Gauge>& Registry::Add(const std::string& name,
+                                      const std::string& help,
+                                      const Labels& labels);
 
-template Family<Summary>& Registry::Add(
-    const std::string& name, const std::string& help,
-    const std::map<std::string, std::string>& labels);
+template Family<Summary>& Registry::Add(const std::string& name,
+                                        const std::string& help,
+                                        const Labels& labels);
 
-template Family<Histogram>& Registry::Add(
-    const std::string& name, const std::string& help,
-    const std::map<std::string, std::string>& labels);
+template Family<Histogram>& Registry::Add(const std::string& name,
+                                          const std::string& help,
+                                          const Labels& labels);
 
 }  // namespace prometheus