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// 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();
}
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