YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

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// The following only applies to changes made to this file as part of YugaByte development.

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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except

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// Unless required by applicable law or agreed to in writing, software distributed under the License

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#include <vector>

#include <gtest/gtest.h>

#include "yb/gutil/ref_counted.h"

#include "yb/gutil/stl_util.h"

#include "yb/util/hdr_histogram.h"

#include "yb/util/status.h"

#include "yb/util/status_log.h"

#include "yb/util/test_util.h"

#include "yb/util/thread.h"

DEFINE_int32(histogram_test_num_threads, 16,

    "Number of threads to spawn for mt-hdr_histogram test");

DEFINE_uint64(histogram_test_num_increments_per_thread, 100000LU,

    "Number of times to call Increment() per thread in mt-hdr_histogram test");

using std::vector;

namespace yb {

class MtHdrHistogramTest : public YBTest {

 public:

  MtHdrHistogramTest() {

    num_threads_ = FLAGS_histogram_test_num_threads;

    num_times_ = FLAGS_histogram_test_num_increments_per_thread;

  }

 protected:

  int num_threads_;

  uint64_t num_times_;

};

// Increment a counter a bunch of times in the same bucket

static void IncrementSameHistValue(HdrHistogram* hist, uint64_t value, uint64_t times) {

  for (uint64_t i = 0; i < times; i++) {

    hist->Increment(value);

  }

}

TEST_F(MtHdrHistogramTest, ConcurrentWriteTest) {

  const uint64_t kValue = 1LU;

  HdrHistogram hist(100000LU, 3);

  auto threads = new scoped_refptr<yb::Thread>[num_threads_];

  for (int i = 0; i < num_threads_; i++) {

    CHECK_OK(yb::Thread::Create("test", strings::Substitute("thread-$0", i),

        IncrementSameHistValue, &hist, kValue, num_times_, &threads[i]));

  }

  for (int i = 0; i < num_threads_; i++) {

    CHECK_OK(ThreadJoiner(threads[i].get()).Join());

  }

  HdrHistogram snapshot(hist);

  ASSERT_EQ(num_threads_ * num_times_, snapshot.CountInBucketForValue(kValue));

  delete[] threads;

}

// Copy while writing, then iterate to ensure copies are consistent.

TEST_F(MtHdrHistogramTest, ConcurrentCopyWhileWritingTest) {

  const int kNumCopies = 10;

  const uint64_t kValue = 1;

  HdrHistogram hist(100000LU, 3);

  auto threads = new scoped_refptr<yb::Thread>[num_threads_];

  for (int i = 0; i < num_threads_; i++) {

    CHECK_OK(yb::Thread::Create("test", strings::Substitute("thread-$0", i),

        IncrementSameHistValue, &hist, kValue, num_times_, &threads[i]));

  }

  // This is somewhat racy but the goal is to catch this issue at least

  // most of the time. At the time of this writing, before fixing a bug where

  // the total count stored in a copied histogram may not match its internal

  // counts (under concurrent writes), this test fails for me on 100/100 runs.

  vector<HdrHistogram *> snapshots;

  ElementDeleter deleter(&snapshots);

  for (int i = 0; i < kNumCopies; i++) {

    snapshots.push_back(new HdrHistogram(hist));

    SleepFor(MonoDelta::FromMicroseconds(100));

  }

  for (int i = 0; i < kNumCopies; i++) {

    snapshots[i]->MeanValue(); // Will crash if underlying iterator is inconsistent.

  }

  for (int i = 0; i < num_threads_; i++) {

    CHECK_OK(ThreadJoiner(threads[i].get()).Join());

  }

  delete[] threads;

}

} // namespace yb