Stats: Add for each iteration for histograms

envoy/stats/store.h

@@ -67,6 +67,7 @@ class Store : public Scope {
   virtual void forEachCounter(SizeFn f_size, StatFn<Counter> f_stat) const PURE;
   virtual void forEachGauge(SizeFn f_size, StatFn<Gauge> f_stat) const PURE;
   virtual void forEachTextReadout(SizeFn f_size, StatFn<TextReadout> f_stat) const PURE;
+  virtual void forEachHistogram(SizeFn f_size, StatFn<ParentHistogram> f_stat) const PURE;
   virtual void forEachScope(SizeFn f_size, StatFn<const Scope> f_stat) const PURE;
 
   /**

source/common/stats/isolated_store_impl.h

@@ -227,6 +227,11 @@ class IsolatedStoreImpl : public StoreImpl {
     text_readouts_.forEachStat(f_size, f_stat);
   }
 
+  void forEachHistogram(SizeFn f_size, StatFn<ParentHistogram> f_stat) const override {
+    UNREFERENCED_PARAMETER(f_size);
+    UNREFERENCED_PARAMETER(f_stat);
+  }
+
   void forEachScope(SizeFn f_size, StatFn<const Scope> f_stat) const override {
     if (f_size != nullptr) {
       f_size(1);

source/common/stats/thread_local_store.cc

@@ -179,14 +179,10 @@ std::vector<TextReadoutSharedPtr> ThreadLocalStoreImpl::textReadouts() const {
 
 std::vector<ParentHistogramSharedPtr> ThreadLocalStoreImpl::histograms() const {
   std::vector<ParentHistogramSharedPtr> ret;
-  Thread::LockGuard lock(hist_mutex_);
-  {
-    ret.reserve(histogram_set_.size());
-    for (const auto& histogram_ptr : histogram_set_) {
-      ret.emplace_back(histogram_ptr);
-    }
-  }
-
+  forEachHistogram([&ret](std::size_t size) mutable { ret.reserve(size); },
+                   [&ret](ParentHistogram& histogram) mutable {
+                     ret.emplace_back(ParentHistogramSharedPtr(&histogram));
+                   });
   return ret;
 }
 
@@ -241,9 +237,7 @@ void ThreadLocalStoreImpl::mergeHistograms(PostMergeCb merge_complete_cb) {
 
 void ThreadLocalStoreImpl::mergeInternal(PostMergeCb merge_complete_cb) {
   if (!shutting_down_) {
-    for (const ParentHistogramSharedPtr& histogram : histograms()) {
-      histogram->merge();
-    }
+    forEachHistogram(nullptr, [](ParentHistogram& histogram) { histogram.merge(); });
     merge_complete_cb();
     merge_in_progress_ = false;
   }
@@ -967,6 +961,16 @@ void ThreadLocalStoreImpl::forEachTextReadout(SizeFn f_size, StatFn<TextReadout>
   alloc_.forEachTextReadout(f_size, f_stat);
 }
 
+void ThreadLocalStoreImpl::forEachHistogram(SizeFn f_size, StatFn<ParentHistogram> f_stat) const {
+  Thread::LockGuard lock(hist_mutex_);
+  if (f_size != nullptr) {
+    f_size(histogram_set_.size());
+  }
+  for (auto histogram : histogram_set_) {
+    f_stat(*histogram);
+  }
+}
+
 void ThreadLocalStoreImpl::forEachScope(std::function<void(std::size_t)> f_size,
                                         StatFn<const Scope> f_scope) const {
   Thread::LockGuard lock(lock_);

source/common/stats/thread_local_store.h

@@ -247,6 +247,7 @@ class ThreadLocalStoreImpl : Logger::Loggable<Logger::Id::stats>, public StoreRo
   void forEachCounter(SizeFn f_size, StatFn<Counter> f_stat) const override;
   void forEachGauge(SizeFn f_size, StatFn<Gauge> f_stat) const override;
   void forEachTextReadout(SizeFn f_size, StatFn<TextReadout> f_stat) const override;
+  void forEachHistogram(SizeFn f_size, StatFn<ParentHistogram> f_stat) const override;
   void forEachScope(SizeFn f_size, StatFn<const Scope> f_stat) const override;
 
   // Stats::StoreRoot

source/server/server.cc

@@ -180,34 +180,38 @@ void InstanceImpl::failHealthcheck(bool fail) {
 
 MetricSnapshotImpl::MetricSnapshotImpl(Stats::Store& store, TimeSource& time_source) {
   store.forEachSinkedCounter(
-      [this](std::size_t size) mutable {
+      [this](std::size_t size) {
         snapped_counters_.reserve(size);
         counters_.reserve(size);
       },
-      [this](Stats::Counter& counter) mutable {
+      [this](Stats::Counter& counter) {
         snapped_counters_.push_back(Stats::CounterSharedPtr(&counter));
         counters_.push_back({counter.latch(), counter});
       });
 
   store.forEachSinkedGauge(
-      [this](std::size_t size) mutable {
+      [this](std::size_t size) {
         snapped_gauges_.reserve(size);
         gauges_.reserve(size);
       },
-      [this](Stats::Gauge& gauge) mutable {
+      [this](Stats::Gauge& gauge) {
         ASSERT(gauge.importMode() != Stats::Gauge::ImportMode::Uninitialized);
         snapped_gauges_.push_back(Stats::GaugeSharedPtr(&gauge));
         gauges_.push_back(gauge);
       });
 
-  snapped_histograms_ = store.histograms();
-  histograms_.reserve(snapped_histograms_.size());
-  for (const auto& histogram : snapped_histograms_) {
-    histograms_.push_back(*histogram);
-  }
+  store.forEachHistogram(
+      [this](std::size_t size) {
+        snapped_histograms_.reserve(size);
+        histograms_.reserve(size);
+      },
+      [this](Stats::ParentHistogram& histogram) {
+        snapped_histograms_.push_back(Stats::ParentHistogramSharedPtr(&histogram));
+        histograms_.push_back(histogram);
+      });
 
   store.forEachSinkedTextReadout(
-      [this](std::size_t size) mutable {
+      [this](std::size_t size) {
         snapped_text_readouts_.reserve(size);
         text_readouts_.reserve(size);
       },