From 5e642085cdce1157e21ed40900782bdd6dbb4af6 Mon Sep 17 00:00:00 2001
From: Jupp Mueller <jupp0r@gmail.com>
Date: Thu, 19 Dec 2019 14:04:37 -0800
Subject: [PATCH] Fix interior mutablility problems

---
 core/include/prometheus/detail/time_window_quantiles.h | 10 +++++-----
 core/include/prometheus/family.h                       |  4 ++--
 core/include/prometheus/registry.h                     |  2 +-
 core/include/prometheus/summary.h                      |  2 +-
 core/src/detail/time_window_quantiles.cc               |  4 ++--
 core/src/family.cc                                     |  2 +-
 6 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/core/include/prometheus/detail/time_window_quantiles.h b/core/include/prometheus/detail/time_window_quantiles.h
index d2a90c31..3a3ac65c 100644
--- a/core/include/prometheus/detail/time_window_quantiles.h
+++ b/core/include/prometheus/detail/time_window_quantiles.h
@@ -17,17 +17,17 @@ class PROMETHEUS_CPP_CORE_EXPORT TimeWindowQuantiles {
   TimeWindowQuantiles(const std::vector<CKMSQuantiles::Quantile>& quantiles,
                       Clock::duration max_age_seconds, int age_buckets);
 
-  double get(double q);
+  double get(double q) const;
   void insert(double value);
 
  private:
-  CKMSQuantiles& rotate();
+  CKMSQuantiles& rotate() const;
 
   const std::vector<CKMSQuantiles::Quantile>& quantiles_;
-  std::vector<CKMSQuantiles> ckms_quantiles_;
-  std::size_t current_bucket_;
+  mutable std::vector<CKMSQuantiles> ckms_quantiles_;
+  mutable std::size_t current_bucket_;
 
-  Clock::time_point last_rotation_;
+  mutable Clock::time_point last_rotation_;
   const Clock::duration rotation_interval_;
 };
 
diff --git a/core/include/prometheus/family.h b/core/include/prometheus/family.h
index 1c05c69f..aa946832 100644
--- a/core/include/prometheus/family.h
+++ b/core/include/prometheus/family.h
@@ -143,9 +143,9 @@ class PROMETHEUS_CPP_CORE_EXPORT Family : public Collectable {
   const std::string name_;
   const std::string help_;
   const std::map<std::string, std::string> constant_labels_;
-  std::mutex mutex_;
+  mutable std::mutex mutex_;
 
-  ClientMetric CollectMetric(std::size_t hash, T* metric);
+  ClientMetric CollectMetric(std::size_t hash, T* metric) const;
   T& Add(const std::map<std::string, std::string>& labels,
          std::unique_ptr<T> object);
 };
diff --git a/core/include/prometheus/registry.h b/core/include/prometheus/registry.h
index 433a1e34..c8fdeb20 100644
--- a/core/include/prometheus/registry.h
+++ b/core/include/prometheus/registry.h
@@ -92,7 +92,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Registry : public Collectable {
   std::vector<std::unique_ptr<Family<Gauge>>> gauges_;
   std::vector<std::unique_ptr<Family<Histogram>>> histograms_;
   std::vector<std::unique_ptr<Family<Summary>>> summaries_;
-  std::mutex mutex_;
+  mutable std::mutex mutex_;
 };
 
 }  // namespace prometheus
diff --git a/core/include/prometheus/summary.h b/core/include/prometheus/summary.h
index 80ce7d6e..7f6a4556 100644
--- a/core/include/prometheus/summary.h
+++ b/core/include/prometheus/summary.h
@@ -85,7 +85,7 @@ class PROMETHEUS_CPP_CORE_EXPORT Summary {
 
  private:
   const Quantiles quantiles_;
-  std::mutex mutex_;
+  mutable std::mutex mutex_;
   std::uint64_t count_;
   double sum_;
   detail::TimeWindowQuantiles quantile_values_;
diff --git a/core/src/detail/time_window_quantiles.cc b/core/src/detail/time_window_quantiles.cc
index eec6f2d3..e767122d 100644
--- a/core/src/detail/time_window_quantiles.cc
+++ b/core/src/detail/time_window_quantiles.cc
@@ -12,7 +12,7 @@ TimeWindowQuantiles::TimeWindowQuantiles(
       last_rotation_(Clock::now()),
       rotation_interval_(max_age / age_buckets) {}
 
-double TimeWindowQuantiles::get(double q) {
+double TimeWindowQuantiles::get(double q) const {
   CKMSQuantiles& current_bucket = rotate();
   return current_bucket.get(q);
 }
@@ -24,7 +24,7 @@ void TimeWindowQuantiles::insert(double value) {
   }
 }
 
-CKMSQuantiles& TimeWindowQuantiles::rotate() {
+CKMSQuantiles& TimeWindowQuantiles::rotate() const {
   auto delta = Clock::now() - last_rotation_;
   while (delta > rotation_interval_) {
     ckms_quantiles_[current_bucket_].reset();
diff --git a/core/src/family.cc b/core/src/family.cc
index eebe18ec..83631abc 100644
--- a/core/src/family.cc
+++ b/core/src/family.cc
@@ -82,7 +82,7 @@ std::vector<MetricFamily> Family<T>::Collect() const {
 }
 
 template <typename T>
-ClientMetric Family<T>::CollectMetric(std::size_t hash, T* metric) {
+ClientMetric Family<T>::CollectMetric(std::size_t hash, T* metric) const {
   auto collected = metric->Collect();
   auto add_label =
       [&collected](const std::pair<std::string, std::string>& label_pair) {