Merge multiple histogram snapshots into single one for reporting.

base/metrics/histogram_snapshot_manager_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/histogram_snapshot_manager.h"
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/metrics/histogram_delta_serialization.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/metrics/sample_vector.h"
 #include "base/metrics/statistics_recorder.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 class HistogramFlattenerDeltaRecorder : public HistogramFlattener {
  public:
   HistogramFlattenerDeltaRecorder() {}
 
   void RecordDelta(const HistogramBase& histogram,
                    const HistogramSamples& snapshot) override {
     recorded_delta_histogram_names_.push_back(histogram.histogram_name());
+    ASSERT_EQ(recorded_delta_histogram_sum_.end(),
+              recorded_delta_histogram_sum_.find(
+                  histogram.histogram_name()));
+    // Keep pointer to snapshot for testing. This really isn't ideal but the
+    // snapshot-manager keeps the snapshot alive until it's "forgotten".
+    recorded_delta_histogram_sum_[histogram.histogram_name()] = snapshot.sum();
   }
 
   void InconsistencyDetected(HistogramBase::Inconsistency problem) override {
     ASSERT_TRUE(false);
   }
 
   void UniqueInconsistencyDetected(
       HistogramBase::Inconsistency problem) override {
     ASSERT_TRUE(false);
   }
 
   void InconsistencyDetectedInLoggedCount(int amount) override {
     ASSERT_TRUE(false);
   }
 
+  void Reset() {
+    recorded_delta_histogram_names_.clear();
+    recorded_delta_histogram_sum_.clear();
+  }
+
   std::vector<std::string> GetRecordedDeltaHistogramNames() {
     return recorded_delta_histogram_names_;
   }
 
+  int64_t GetRecordedDeltaHistogramSum(
+      const std::string& name) {

[Alexei Svitkine (slow), 2016/02/18 15:47:40]

Nit: Fits on previous line?

[bcwhite, 2016/02/18 17:07:04]

Done.

+    EXPECT_NE(recorded_delta_histogram_sum_.end(),
+              recorded_delta_histogram_sum_.find(name));
+    return recorded_delta_histogram_sum_[name];
+  }
+
  private:
   std::vector<std::string> recorded_delta_histogram_names_;
+  std::map<std::string, int64_t> recorded_delta_histogram_sum_;
 
   DISALLOW_COPY_AND_ASSIGN(HistogramFlattenerDeltaRecorder);
 };
 
 class HistogramSnapshotManagerTest : public testing::Test {
  protected:
   HistogramSnapshotManagerTest()
       : histogram_snapshot_manager_(&histogram_flattener_delta_recorder_) {}
 
   ~HistogramSnapshotManagerTest() override {}
 
   StatisticsRecorder statistics_recorder_;
   HistogramFlattenerDeltaRecorder histogram_flattener_delta_recorder_;
   HistogramSnapshotManager histogram_snapshot_manager_;
 };
 
 TEST_F(HistogramSnapshotManagerTest, PrepareDeltasNoFlagsFilter) {
   // kNoFlags filter should record all histograms.
-  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 2);
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
   UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
 
   histogram_snapshot_manager_.PrepareDeltas(
       StatisticsRecorder::begin(false), StatisticsRecorder::end(),
       HistogramBase::kNoFlags, HistogramBase::kNoFlags);
 
   const std::vector<std::string>& histograms =
       histogram_flattener_delta_recorder_.GetRecordedDeltaHistogramNames();
   EXPECT_EQ(2U, histograms.size());
   EXPECT_EQ("UmaHistogram", histograms[0]);
   EXPECT_EQ("UmaStabilityHistogram", histograms[1]);
 }
 
 TEST_F(HistogramSnapshotManagerTest, PrepareDeltasUmaHistogramFlagFilter) {
   // Note that kUmaStabilityHistogramFlag includes kUmaTargetedHistogramFlag.
-  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 2);
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
   UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
 
   histogram_snapshot_manager_.PrepareDeltas(
       StatisticsRecorder::begin(false), StatisticsRecorder::end(),
       HistogramBase::kNoFlags, HistogramBase::kUmaTargetedHistogramFlag);
 
   const std::vector<std::string>& histograms =
       histogram_flattener_delta_recorder_.GetRecordedDeltaHistogramNames();
   EXPECT_EQ(2U, histograms.size());
   EXPECT_EQ("UmaHistogram", histograms[0]);
   EXPECT_EQ("UmaStabilityHistogram", histograms[1]);
 }
 
 TEST_F(HistogramSnapshotManagerTest,
        PrepareDeltasUmaStabilityHistogramFlagFilter) {
-  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 2);
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
   UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
 
   histogram_snapshot_manager_.PrepareDeltas(
       StatisticsRecorder::begin(false), StatisticsRecorder::end(),
       HistogramBase::kNoFlags, HistogramBase::kUmaStabilityHistogramFlag);
 
   const std::vector<std::string>& histograms =
       histogram_flattener_delta_recorder_.GetRecordedDeltaHistogramNames();
   EXPECT_EQ(1U, histograms.size());
   EXPECT_EQ("UmaStabilityHistogram", histograms[0]);
 }
 
+TEST_F(HistogramSnapshotManagerTest, CheckMerge) {
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
+  UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
+
+  base::HistogramBase* h1 = base::LinearHistogram::FactoryGet(
+      "UmaHistogram", 1, 4, 5, 0);
+  ASSERT_TRUE(h1);
+  base::HistogramBase* h2 = base::LinearHistogram::FactoryGet(
+      "UmaStabilityHistogram", 1, 2, 3, 0);
+  ASSERT_TRUE(h2);
+
+  histogram_snapshot_manager_.StartDeltas();
+  histogram_snapshot_manager_.PrepareDelta(h1);
+  histogram_snapshot_manager_.PrepareDelta(h1);  // Delta will be zero.
+  histogram_snapshot_manager_.PrepareDelta(h2);
+  h1->Add(2);
+  h2->Add(1);
+  histogram_snapshot_manager_.PrepareDelta(h2);
+  histogram_snapshot_manager_.PrepareDelta(h1);
+  histogram_snapshot_manager_.FinishDeltas();
+  {
+    const std::vector<std::string>& histograms =

[Alexei Svitkine (slow), 2016/02/18 15:47:40]

Nit: No &

The object is returned by value.

[bcwhite, 2016/02/18 17:07:04]

Done.

+        histogram_flattener_delta_recorder_.GetRecordedDeltaHistogramNames();
+    EXPECT_EQ(2U, histograms.size());
+    EXPECT_EQ(3, histogram_flattener_delta_recorder_.
+                     GetRecordedDeltaHistogramSum("UmaHistogram"));
+    EXPECT_EQ(2, histogram_flattener_delta_recorder_.
+                     GetRecordedDeltaHistogramSum("UmaStabilityHistogram"));
+  }
+}
+
 }  // namespace base