1 files changed, 254 insertions, 0 deletions
diff --git a/src/rocksdb/monitoring/histogram_test.cc b/src/rocksdb/monitoring/histogram_test.cc
new file mode 100644
index 000000000..19e9f15d0
--- /dev/null
+++ b/src/rocksdb/monitoring/histogram_test.cc
@@ -0,0 +1,254 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#include "monitoring/histogram.h"
+
+#include <cmath>
+
+#include "monitoring/histogram_windowing.h"
+#include "rocksdb/system_clock.h"
+#include "test_util/mock_time_env.h"
+#include "test_util/testharness.h"
+#include "util/random.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class HistogramTest : public testing::Test {};
+
+namespace {
+const double kIota = 0.1;
+const HistogramBucketMapper bucketMapper;
+std::shared_ptr<MockSystemClock> clock =
+    std::make_shared<MockSystemClock>(SystemClock::Default());
+}  // namespace
+
+void PopulateHistogram(Histogram& histogram, uint64_t low, uint64_t high,
+                       uint64_t loop = 1) {
+  Random rnd(test::RandomSeed());
+  for (; loop > 0; loop--) {
+    for (uint64_t i = low; i <= high; i++) {
+      histogram.Add(i);
+      // sleep a random microseconds [0-10)
+      clock->SleepForMicroseconds(rnd.Uniform(10));
+    }
+  }
+  // make sure each data population at least take some time
+  clock->SleepForMicroseconds(1);
+}
+
+void BasicOperation(Histogram& histogram) {
+  PopulateHistogram(histogram, 1, 110, 10);  // fill up to bucket [70, 110)
+
+  HistogramData data;
+  histogram.Data(&data);
+
+  ASSERT_LE(fabs(histogram.Percentile(100.0) - 110.0), kIota);
+  ASSERT_LE(fabs(data.percentile99 - 108.9), kIota);  // 99 * 110 / 100
+  ASSERT_LE(fabs(data.percentile95 - 104.5), kIota);  // 95 * 110 / 100
+  ASSERT_LE(fabs(data.median - 55.0), kIota);         // 50 * 110 / 100
+  ASSERT_EQ(data.average, 55.5);                      // (1 + 110) / 2
+}
+
+void MergeHistogram(Histogram& histogram, Histogram& other) {
+  PopulateHistogram(histogram, 1, 100);
+  PopulateHistogram(other, 101, 250);
+  histogram.Merge(other);
+
+  HistogramData data;
+  histogram.Data(&data);
+
+  ASSERT_LE(fabs(histogram.Percentile(100.0) - 250.0), kIota);
+  ASSERT_LE(fabs(data.percentile99 - 247.5), kIota);  // 99 * 250 / 100
+  ASSERT_LE(fabs(data.percentile95 - 237.5), kIota);  // 95 * 250 / 100
+  ASSERT_LE(fabs(data.median - 125.0), kIota);        // 50 * 250 / 100
+  ASSERT_EQ(data.average, 125.5);                     // (1 + 250) / 2
+}
+
+void EmptyHistogram(Histogram& histogram) {
+  ASSERT_EQ(histogram.min(), bucketMapper.LastValue());
+  ASSERT_EQ(histogram.max(), 0);
+  ASSERT_EQ(histogram.num(), 0);
+  ASSERT_EQ(histogram.Median(), 0.0);
+  ASSERT_EQ(histogram.Percentile(85.0), 0.0);
+  ASSERT_EQ(histogram.Average(), 0.0);
+  ASSERT_EQ(histogram.StandardDeviation(), 0.0);
+}
+
+void ClearHistogram(Histogram& histogram) {
+  for (uint64_t i = 1; i <= 100; i++) {
+    histogram.Add(i);
+  }
+  histogram.Clear();
+  ASSERT_TRUE(histogram.Empty());
+  ASSERT_EQ(histogram.Median(), 0);
+  ASSERT_EQ(histogram.Percentile(85.0), 0);
+  ASSERT_EQ(histogram.Average(), 0);
+}
+
+TEST_F(HistogramTest, BasicOperation) {
+  HistogramImpl histogram;
+  BasicOperation(histogram);
+
+  HistogramWindowingImpl histogramWindowing;
+  BasicOperation(histogramWindowing);
+}
+
+TEST_F(HistogramTest, BoundaryValue) {
+  HistogramImpl histogram;
+  // - both should be in [0, 1] bucket because we place values on bucket
+  //   boundaries in the lower bucket.
+  // - all points are in [0, 1] bucket, so p50 will be 0.5
+  // - the test cannot be written with a single point since histogram won't
+  //   report percentiles lower than the min or greater than the max.
+  histogram.Add(0);
+  histogram.Add(1);
+
+  ASSERT_LE(fabs(histogram.Percentile(50.0) - 0.5), kIota);
+}
+
+TEST_F(HistogramTest, MergeHistogram) {
+  HistogramImpl histogram;
+  HistogramImpl other;
+  MergeHistogram(histogram, other);
+
+  HistogramWindowingImpl histogramWindowing;
+  HistogramWindowingImpl otherWindowing;
+  MergeHistogram(histogramWindowing, otherWindowing);
+}
+
+TEST_F(HistogramTest, EmptyHistogram) {
+  HistogramImpl histogram;
+  EmptyHistogram(histogram);
+
+  HistogramWindowingImpl histogramWindowing;
+  EmptyHistogram(histogramWindowing);
+}
+
+TEST_F(HistogramTest, ClearHistogram) {
+  HistogramImpl histogram;
+  ClearHistogram(histogram);
+
+  HistogramWindowingImpl histogramWindowing;
+  ClearHistogram(histogramWindowing);
+}
+
+TEST_F(HistogramTest, HistogramWindowingExpire) {
+  uint64_t num_windows = 3;
+  int micros_per_window = 1000000;
+  uint64_t min_num_per_window = 0;
+
+  HistogramWindowingImpl histogramWindowing(num_windows, micros_per_window,
+                                            min_num_per_window);
+  histogramWindowing.TEST_UpdateClock(clock);
+  PopulateHistogram(histogramWindowing, 1, 1, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+  ASSERT_EQ(histogramWindowing.num(), 100);
+  ASSERT_EQ(histogramWindowing.min(), 1);
+  ASSERT_EQ(histogramWindowing.max(), 1);
+  ASSERT_EQ(histogramWindowing.Average(), 1.0);
+  ASSERT_EQ(histogramWindowing.StandardDeviation(), 0.0);
+
+  PopulateHistogram(histogramWindowing, 2, 2, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+  ASSERT_EQ(histogramWindowing.num(), 200);
+  ASSERT_EQ(histogramWindowing.min(), 1);
+  ASSERT_EQ(histogramWindowing.max(), 2);
+  ASSERT_EQ(histogramWindowing.Average(), 1.5);
+  ASSERT_GT(histogramWindowing.StandardDeviation(), 0.0);
+
+  PopulateHistogram(histogramWindowing, 3, 3, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+  ASSERT_EQ(histogramWindowing.num(), 300);
+  ASSERT_EQ(histogramWindowing.min(), 1);
+  ASSERT_EQ(histogramWindowing.max(), 3);
+  ASSERT_EQ(histogramWindowing.Average(), 2.0);
+  ASSERT_GT(histogramWindowing.StandardDeviation(), 0.0);
+
+  // dropping oldest window with value 1, remaining 2 ~ 4
+  PopulateHistogram(histogramWindowing, 4, 4, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+  ASSERT_EQ(histogramWindowing.num(), 300);
+  ASSERT_EQ(histogramWindowing.min(), 2);
+  ASSERT_EQ(histogramWindowing.max(), 4);
+  ASSERT_EQ(histogramWindowing.Average(), 3.0);
+  ASSERT_GT(histogramWindowing.StandardDeviation(), 0.0);
+
+  // dropping oldest window with value 2, remaining 3 ~ 5
+  PopulateHistogram(histogramWindowing, 5, 5, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+  ASSERT_EQ(histogramWindowing.num(), 300);
+  ASSERT_EQ(histogramWindowing.min(), 3);
+  ASSERT_EQ(histogramWindowing.max(), 5);
+  ASSERT_EQ(histogramWindowing.Average(), 4.0);
+  ASSERT_GT(histogramWindowing.StandardDeviation(), 0.0);
+}
+
+TEST_F(HistogramTest, HistogramWindowingMerge) {
+  uint64_t num_windows = 3;
+  int micros_per_window = 1000000;
+  uint64_t min_num_per_window = 0;
+
+  HistogramWindowingImpl histogramWindowing(num_windows, micros_per_window,
+                                            min_num_per_window);
+  HistogramWindowingImpl otherWindowing(num_windows, micros_per_window,
+                                        min_num_per_window);
+  histogramWindowing.TEST_UpdateClock(clock);
+  otherWindowing.TEST_UpdateClock(clock);
+
+  PopulateHistogram(histogramWindowing, 1, 1, 100);
+  PopulateHistogram(otherWindowing, 1, 1, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+
+  PopulateHistogram(histogramWindowing, 2, 2, 100);
+  PopulateHistogram(otherWindowing, 2, 2, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+
+  PopulateHistogram(histogramWindowing, 3, 3, 100);
+  PopulateHistogram(otherWindowing, 3, 3, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+
+  histogramWindowing.Merge(otherWindowing);
+  ASSERT_EQ(histogramWindowing.num(), 600);
+  ASSERT_EQ(histogramWindowing.min(), 1);
+  ASSERT_EQ(histogramWindowing.max(), 3);
+  ASSERT_EQ(histogramWindowing.Average(), 2.0);
+
+  // dropping oldest window with value 1, remaining 2 ~ 4
+  PopulateHistogram(histogramWindowing, 4, 4, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+  ASSERT_EQ(histogramWindowing.num(), 500);
+  ASSERT_EQ(histogramWindowing.min(), 2);
+  ASSERT_EQ(histogramWindowing.max(), 4);
+
+  // dropping oldest window with value 2, remaining 3 ~ 5
+  PopulateHistogram(histogramWindowing, 5, 5, 100);
+  clock->SleepForMicroseconds(micros_per_window);
+  ASSERT_EQ(histogramWindowing.num(), 400);
+  ASSERT_EQ(histogramWindowing.min(), 3);
+  ASSERT_EQ(histogramWindowing.max(), 5);
+}
+
+TEST_F(HistogramTest, LargeStandardDeviation) {
+  HistogramImpl histogram;
+  PopulateHistogram(histogram, 1, 1000000);
+  ASSERT_LT(fabs(histogram.StandardDeviation() - 288675), 1);
+}
+
+TEST_F(HistogramTest, LostUpdateStandardDeviation) {
+  HistogramImpl histogram;
+  PopulateHistogram(histogram, 100, 100, 100);
+  // Simulate a possible lost update (since they are not atomic)
+  histogram.TEST_GetStats().sum_squares_ -= 10000;
+  // Ideally zero, but should never be negative or NaN
+  ASSERT_GE(histogram.StandardDeviation(), 0.0);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}