registry_counters_reset.patch

diff --git a/core/include/prometheus/counter.h b/core/include/prometheus/counter.h
index 9b2ad19..4fa1fba 100644
--- a/core/include/prometheus/counter.h
+++ b/core/include/prometheus/counter.h
@@ -46,6 +46,12 @@ class PROMETHEUS_CPP_CORE_EXPORT Counter {
   /// Collect is called by the Registry when collecting metrics.
   ClientMetric Collect() const;
 
+  /// \brief Reset this counter metric to a value of 'zero'.
+  ///
+  /// This function shall only be used in case of 'PROXYSQL STOP' operation
+  /// which invalidates all ProxySQL internal counters for a fresh start.
+  void Reset();
+
  private:
   Gauge gauge_{0.0};
 };
diff --git a/core/include/prometheus/family.h b/core/include/prometheus/family.h
index 0bc0723..4f62fda 100644
--- a/core/include/prometheus/family.h
+++ b/core/include/prometheus/family.h
@@ -141,6 +141,12 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   /// \return Zero or more samples for each dimensional data.
   std::vector<MetricFamily> Collect() const override;
 
+  /// \brief Reset all the metrics hold within this specific family.
+  ///
+  /// This function shall only be used in case of 'PROXYSQL STOP' operation
+  /// which invalidates all ProxySQL internal counters for a fresh start.
+  void ResetMetrics();
+
  private:
   std::unordered_map<Labels, std::unique_ptr<T>, detail::LabelHasher> metrics_;
 
diff --git a/core/include/prometheus/registry.h b/core/include/prometheus/registry.h
index 6603f6c..877c085 100644
--- a/core/include/prometheus/registry.h
+++ b/core/include/prometheus/registry.h
@@ -94,6 +94,12 @@ class PROMETHEUS_CPP_CORE_EXPORT Registry : public Collectable {
   template <typename T>
   bool Remove(const Family<T>& family);
 
+  /// \brief Reset all the counters hold within the registry to a value of zero.
+  ///
+  /// This function shall only be used in case of 'PROXYSQL STOP' operation
+  /// which invalidates all ProxySQL internal counters for a fresh start.
+  void ResetCounters();
+
  private:
   template <typename T>
   friend class detail::Builder;
diff --git a/core/src/counter.cc b/core/src/counter.cc
index 2a93463..a12885d 100644
--- a/core/src/counter.cc
+++ b/core/src/counter.cc
@@ -13,6 +13,8 @@ void Counter::Increment(const double val) {
 
 double Counter::Value() const { return gauge_.Value(); }
 
+void Counter::Reset() { gauge_.Set(0.0); }
+
 ClientMetric Counter::Collect() const {
   ClientMetric metric;
   metric.counter.value = Value();
diff --git a/core/src/family.cc b/core/src/family.cc
index f087586..8f9d276 100644
--- a/core/src/family.cc
+++ b/core/src/family.cc
@@ -122,6 +122,19 @@ ClientMetric Family<T>::CollectMetric(const Labels& metric_labels,
   return collected;
 }
 
+template <>
+void Family<Counter>::ResetMetrics() {
+//  const auto reset_metric =
+//      [](std::pair<const std::size_t, std::unique_ptr<Counter>>& metric) {
+//          metric.second->Reset();
+//      };
+//
+//  std::for_each(metrics_.begin(), metrics_.end(), reset_metric);
+  for (const auto& m : metrics_) {
+    m.second->Reset();
+  }
+}
+
 template class PROMETHEUS_CPP_CORE_EXPORT Family<Counter>;
 template class PROMETHEUS_CPP_CORE_EXPORT Family<Gauge>;
 template class PROMETHEUS_CPP_CORE_EXPORT Family<Histogram>;
diff --git a/core/src/registry.cc b/core/src/registry.cc
index 267bf92..7a365ed 100644
--- a/core/src/registry.cc
+++ b/core/src/registry.cc
@@ -56,6 +56,12 @@ std::vector<MetricFamily> Registry::Collect() const {
   return results;
 }
 
+void Registry::ResetCounters(){
+	for (auto& family : this->counters_) {
+		family->ResetMetrics();
+	}
+}
+
 template <>
 std::vector<std::unique_ptr<Family<Counter>>>& Registry::GetFamilies() {
   return counters_;