// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#include "kudu/util/metrics.h"

#include <cstdint>
#include <functional>
#include <map>
#include <memory>
#include <ostream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#include <gflags/gflags_declare.h>
#include <glog/logging.h>
#include <gtest/gtest.h>
#include <rapidjson/document.h>

#include "kudu/gutil/casts.h"
#include "kudu/gutil/map-util.h"
#include "kudu/gutil/ref_counted.h"
#include "kudu/util/hdr_histogram.h"
#include "kudu/util/jsonreader.h"
#include "kudu/util/jsonwriter.h"
#include "kudu/util/monotime.h"
#include "kudu/util/oid_generator.h"
#include "kudu/util/prometheus_writer.h"
#include "kudu/util/random.h"
#include "kudu/util/status.h"
#include "kudu/util/test_macros.h"
#include "kudu/util/test_util.h"

using std::string;
using std::unordered_map;
using std::unordered_set;
using std::vector;

DECLARE_int32(metrics_retirement_age_ms);

DECLARE_string(metrics_default_level);

namespace kudu {

METRIC_DEFINE_entity(test_entity);

class MetricsTest : public KuduTest {
 public:
  void SetUp() override {
    KuduTest::SetUp();

    entity_ = METRIC_ENTITY_test_entity.Instantiate(&registry_, "my-test-same-attr1");
    entity_->SetAttribute("attr_for_merge", "same_attr");

    entity_same_attr_ = METRIC_ENTITY_test_entity.Instantiate(&registry_, "my-test-same-attr2");
    entity_same_attr_->SetAttribute("attr_for_merge", "same_attr");

    entity_diff_attr_ = METRIC_ENTITY_test_entity.Instantiate(&registry_, "my-test-diff-attr");
    entity_diff_attr_->SetAttribute("attr_for_merge", "diff_attr");
  }

 protected:
  const int kEntityCount = 3;

  MetricRegistry registry_;
  scoped_refptr<MetricEntity> entity_;
  scoped_refptr<MetricEntity> entity_same_attr_;
  scoped_refptr<MetricEntity> entity_diff_attr_;
};

METRIC_DEFINE_counter(test_entity, test_counter, "My Test Counter", MetricUnit::kRequests,
                      "Description of test counter",
                      kudu::MetricLevel::kInfo);

TEST_F(MetricsTest, SimpleCounterTest) {
  scoped_refptr<Counter> requests =
    new Counter(&METRIC_test_counter);
  ASSERT_EQ("Description of test counter", requests->prototype()->description());
  ASSERT_EQ(0, requests->value());
  requests->Increment();
  ASSERT_EQ(1, requests->value());
  requests->IncrementBy(2);
  ASSERT_EQ(3, requests->value());
}

TEST_F(MetricsTest, SimpleCounterMergeTest) {
  scoped_refptr<Counter> requests =
    new Counter(&METRIC_test_counter);
  scoped_refptr<Counter> requests_for_merge =
    new Counter(&METRIC_test_counter);
  requests->IncrementBy(2);
  requests_for_merge->IncrementBy(3);
  requests_for_merge->MergeFrom(requests);
  ASSERT_EQ(2, requests->value());
  ASSERT_EQ(5, requests_for_merge->value());
  requests->IncrementBy(7);
  requests_for_merge->MergeFrom(requests);
  ASSERT_EQ(9, requests->value());
  ASSERT_EQ(14, requests_for_merge->value());
  requests_for_merge->MergeFrom(requests_for_merge);
  ASSERT_EQ(14, requests_for_merge->value());
}

TEST_F(MetricsTest, ResetCounter) {
  scoped_refptr<Counter> c(new Counter(&METRIC_test_counter));
  ASSERT_EQ(0, c->value());
  c->Increment();
  ASSERT_EQ(1, c->value());
  c->Reset();
  ASSERT_EQ(0, c->value());
  c->IncrementBy(2);
  ASSERT_EQ(2, c->value());
  c->IncrementBy(-1);
  ASSERT_EQ(1, c->value());
  c->Reset();
  ASSERT_EQ(0, c->value());
}

TEST_F(MetricsTest, CounterPrometheusTest) {
  scoped_refptr<Counter> requests =
    new Counter(&METRIC_test_counter);

  std::ostringstream output;
  string prefix;
  PrometheusWriter writer(&output);
  ASSERT_OK(requests->WriteAsPrometheus(&writer, prefix));

  const string expected_output = "# HELP test_counter Description of test counter\n"
                                 "# TYPE test_counter counter\n"
                                 "test_counter{unit_type=\"requests\"} 0\n";

  ASSERT_EQ(expected_output, output.str());
}

METRIC_DEFINE_gauge_string(test_entity, test_string_gauge, "Test string Gauge",
                           MetricUnit::kState, "Description of string Gauge",
                           kudu::MetricLevel::kInfo);

TEST_F(MetricsTest, SimpleStringGaugeTest) {
  scoped_refptr<StringGauge> state =
    new StringGauge(&METRIC_test_string_gauge, "Healthy");
  ASSERT_EQ(METRIC_test_string_gauge.description(), state->prototype()->description());
  ASSERT_EQ("Healthy", state->value());
  state->set_value("Under-replicated");
  ASSERT_EQ("Under-replicated", state->value());
  state->set_value("Recovering");
  ASSERT_EQ("Recovering", state->value());
}

TEST_F(MetricsTest, SimpleStringGaugeForMergeTest) {
  scoped_refptr<StringGauge> state =
    new StringGauge(&METRIC_test_string_gauge, "Healthy");
  scoped_refptr<StringGauge> state_for_merge =
    new StringGauge(&METRIC_test_string_gauge, "Recovering");
  state_for_merge->MergeFrom(state);
  ASSERT_EQ("Healthy", state->value());
  ASSERT_EQ(unordered_set<string>({"Recovering", "Healthy"}),
            state_for_merge->unique_values());

  scoped_refptr<StringGauge> state_old =
      down_cast<StringGauge*>(state->snapshot().get());
  ASSERT_EQ("Healthy", state_old->value());
  scoped_refptr<StringGauge> state_for_merge_old =
      down_cast<StringGauge*>(state_for_merge->snapshot().get());
  ASSERT_EQ(unordered_set<string>({"Recovering", "Healthy"}),
            state_for_merge_old->unique_values());

  state_old->set_value("Unavailable");
  ASSERT_EQ("Unavailable", state_old->value());
  state_for_merge_old->MergeFrom(state_old);
  ASSERT_EQ(unordered_set<string>({"Unavailable", "Recovering", "Healthy"}),
            state_for_merge_old->unique_values());

  state->set_value("Under-replicated");
  state_for_merge->MergeFrom(state);
  ASSERT_EQ(unordered_set<string>({"Under-replicated", "Healthy", "Recovering"}),
            state_for_merge->unique_values());

  state_for_merge->MergeFrom(state_for_merge_old);
  ASSERT_EQ(unordered_set<string>({"Unavailable", "Healthy", "Recovering"}),
            state_for_merge_old->unique_values());
  ASSERT_EQ(unordered_set<string>({"Unavailable", "Under-replicated", "Healthy", "Recovering"}),
            state_for_merge->unique_values());

  state_for_merge->MergeFrom(state_for_merge);
  ASSERT_EQ(unordered_set<string>({"Unavailable", "Under-replicated", "Healthy", "Recovering"}),
            state_for_merge->unique_values());
}

TEST_F(MetricsTest, StringGaugePrometheusTest) {
  scoped_refptr<StringGauge> state =
    new StringGauge(&METRIC_test_string_gauge, "Healthy");

  std::ostringstream output;
  string prefix;
  PrometheusWriter writer(&output);
  ASSERT_OK(state->WriteAsPrometheus(&writer, prefix));
  // String Gauges are not representable in Prometheus, empty output is expected
  ASSERT_EQ("", output.str());
}

METRIC_DEFINE_gauge_double(test_entity, test_mean_gauge, "Test mean Gauge",
                           MetricUnit::kUnits, "Description of mean Gauge",
                           kudu::MetricLevel::kInfo);

TEST_F(MetricsTest, SimpleMeanGaugeTest) {
  scoped_refptr<MeanGauge> average_usage =
    METRIC_test_mean_gauge.InstantiateMeanGauge(entity_);
  ASSERT_EQ(METRIC_test_mean_gauge.description(), average_usage->prototype()->description());
  ASSERT_EQ(0, average_usage->value());
  average_usage->set_value(10.0, 2.0);
  ASSERT_EQ(5, average_usage->value());
  average_usage->set_value(5.0, 2.0);
  ASSERT_EQ(2.5, average_usage->value());
}

TEST_F(MetricsTest, SimpleMeanGaugeSnapshotTest) {
  scoped_refptr<MeanGauge> average_usage =
    METRIC_test_mean_gauge.InstantiateMeanGauge(entity_);
  scoped_refptr<MeanGauge> old_metric =
    down_cast<MeanGauge*>(average_usage->snapshot().get());
  ASSERT_EQ(0, old_metric->value());
  average_usage->set_value(10.0, 2.0);
  scoped_refptr<MeanGauge> new_metric =
    down_cast<MeanGauge*>(average_usage->snapshot().get());
  ASSERT_EQ(5, new_metric->value());
}

TEST_F(MetricsTest, SimpleMeanGaugeMergeTest) {
  scoped_refptr<MeanGauge> average_usage =
    METRIC_test_mean_gauge.InstantiateMeanGauge(entity_);
  scoped_refptr<MeanGauge> average_usage_for_merge =
    METRIC_test_mean_gauge.InstantiateMeanGauge(entity_same_attr_);
  average_usage_for_merge->MergeFrom(average_usage);
  ASSERT_EQ(0, average_usage->value());
  ASSERT_EQ(0, average_usage_for_merge->value());
  average_usage->set_value(10.0, 1.0);
  average_usage_for_merge->set_value(2.0, 2.0);
  ASSERT_EQ(10, average_usage->value());
  ASSERT_EQ(1, average_usage_for_merge->value());
  average_usage_for_merge->MergeFrom(average_usage);
  ASSERT_EQ(10, average_usage->value());
  ASSERT_EQ(4, average_usage_for_merge->value());
  average_usage_for_merge->MergeFrom(average_usage_for_merge);
  ASSERT_EQ(4, average_usage_for_merge->value());
}

TEST_F(MetricsTest, TestMeanGaugeJsonPrint) {
  scoped_refptr<MeanGauge> test_meangauge =
    METRIC_test_mean_gauge.InstantiateMeanGauge(entity_);
  const double kTotalSum = 5.0;
  const double kTotalCount = 2.0;
  test_meangauge->set_value(kTotalSum, kTotalCount);

  std::ostringstream out;
  JsonWriter writer(&out, JsonWriter::PRETTY);
  CHECK_OK(entity_->WriteAsJson(&writer, MetricJsonOptions()));

  JsonReader reader(out.str());
  ASSERT_OK(reader.Init());
  vector<const rapidjson::Value*> metrics;
  ASSERT_OK(reader.ExtractObjectArray(reader.root(), "metrics", &metrics));
  ASSERT_EQ(1, metrics.size());

  double total_sum;
  ASSERT_OK(reader.ExtractDouble(metrics[0], "total_sum", &total_sum));
  double total_count;
  ASSERT_OK(reader.ExtractDouble(metrics[0], "total_count", &total_count));
  double value;
  ASSERT_OK(reader.ExtractDouble(metrics[0], "value", &value));
  ASSERT_EQ(total_sum, kTotalSum);
  ASSERT_EQ(total_count, kTotalCount);
  ASSERT_EQ(value, kTotalSum/kTotalCount);
}


TEST_F(MetricsTest, MeanGaugePrometheusTest) {
  scoped_refptr<MeanGauge> average_usage =
    METRIC_test_mean_gauge.InstantiateMeanGauge(entity_);

  std::ostringstream output;
  string prefix;
  PrometheusWriter writer(&output);
  ASSERT_OK(average_usage->WriteAsPrometheus(&writer, prefix));

  const string expected_output = "# HELP test_mean_gauge Description of mean Gauge\n"
                                 "# TYPE test_mean_gauge gauge\n"
                                 "test_mean_gauge{unit_type=\"units\"} 0\n"
                                 "test_mean_gauge_count{unit_type=\"units\"} 0\n"
                                 "test_mean_gauge_sum{unit_type=\"units\"} 0\n";

  ASSERT_EQ(expected_output, output.str());
}

METRIC_DEFINE_gauge_uint64(test_entity, test_gauge, "Test uint64 Gauge",
                           MetricUnit::kBytes, "Description of Test Gauge",
                           kudu::MetricLevel::kInfo);

METRIC_DEFINE_gauge_bool(test_entity, test_gauge_bool, "Test boolean Gauge",
                           MetricUnit::kState, "Description of Test boolean Gauge",
                           kudu::MetricLevel::kInfo);

TEST_F(MetricsTest, SimpleAtomicGaugeTest) {
  scoped_refptr<AtomicGauge<uint64_t> > mem_usage =
    METRIC_test_gauge.Instantiate(entity_, 0);
  ASSERT_EQ(METRIC_test_gauge.description(), mem_usage->prototype()->description());
  ASSERT_EQ(0, mem_usage->value());
  mem_usage->IncrementBy(7);
  ASSERT_EQ(7, mem_usage->value());
  mem_usage->set_value(5);
  ASSERT_EQ(5, mem_usage->value());
}

TEST_F(MetricsTest, SimpleAtomicGaugeSumTypeMergeTest) {
  scoped_refptr<AtomicGauge<uint64_t> > mem_usage =
      METRIC_test_gauge.Instantiate(entity_, 2);
  scoped_refptr<AtomicGauge<uint64_t> > mem_usage_for_merge =
      METRIC_test_gauge.Instantiate(entity_same_attr_, 3);
  mem_usage_for_merge->MergeFrom(mem_usage);
  ASSERT_EQ(2, mem_usage->value());
  ASSERT_EQ(5, mem_usage_for_merge->value());
  mem_usage->IncrementBy(7);
  mem_usage_for_merge->MergeFrom(mem_usage);
  ASSERT_EQ(9, mem_usage->value());
  ASSERT_EQ(14, mem_usage_for_merge->value());
  mem_usage_for_merge->MergeFrom(mem_usage_for_merge);
  ASSERT_EQ(14, mem_usage_for_merge->value());
}

TEST_F(MetricsTest, SimpleAtomicGaugeMaxTypeMergeTest) {
  scoped_refptr<AtomicGauge<uint64_t> > stop_time =
      METRIC_test_gauge.Instantiate(entity_, 2, MergeType::kMax);
  scoped_refptr<AtomicGauge<uint64_t> > stop_time_for_merge =
      METRIC_test_gauge.Instantiate(entity_same_attr_, 3, MergeType::kMax);
  stop_time_for_merge->MergeFrom(stop_time);
  ASSERT_EQ(2, stop_time->value());
  ASSERT_EQ(3, stop_time_for_merge->value());
  stop_time->IncrementBy(7);
  stop_time_for_merge->MergeFrom(stop_time);
  ASSERT_EQ(9, stop_time->value());
  ASSERT_EQ(9, stop_time_for_merge->value());
  stop_time_for_merge->MergeFrom(stop_time_for_merge);
  ASSERT_EQ(9, stop_time_for_merge->value());
}

TEST_F(MetricsTest, SimpleAtomicGaugeMinTypeMergeTest) {
  scoped_refptr<AtomicGauge<uint64_t> > start_time =
      METRIC_test_gauge.Instantiate(entity_, 3, MergeType::kMin);
  scoped_refptr<AtomicGauge<uint64_t> > start_time_for_merge =
      METRIC_test_gauge.Instantiate(entity_same_attr_, 5, MergeType::kMin);
  start_time_for_merge->MergeFrom(start_time);
  ASSERT_EQ(3, start_time->value());
  ASSERT_EQ(3, start_time_for_merge->value());
  start_time->DecrementBy(2);
  start_time_for_merge->MergeFrom(start_time);
  ASSERT_EQ(1, start_time->value());
  ASSERT_EQ(1, start_time_for_merge->value());
  start_time_for_merge->MergeFrom(start_time_for_merge);
  ASSERT_EQ(1, start_time_for_merge->value());
}

TEST_F(MetricsTest, AtomicGaugePrometheusTest) {
  scoped_refptr<AtomicGauge<uint64_t> > mem_usage =
    METRIC_test_gauge.Instantiate(entity_, 0);

  std::ostringstream output;
  string prefix;
  PrometheusWriter writer(&output);
  ASSERT_OK(mem_usage->WriteAsPrometheus(&writer, prefix));

  const string expected_output = "# HELP test_gauge Description of Test Gauge\n"
                                 "# TYPE test_gauge gauge\n"
                                 "test_gauge{unit_type=\"bytes\"} 0\n";

  ASSERT_EQ(expected_output, output.str());
}

TEST_F(MetricsTest, AtomicGaugeBooleanPrometheusTest) {
  scoped_refptr<AtomicGauge<bool> > clock_extrapolating =
    METRIC_test_gauge_bool.Instantiate(entity_, false);

  std::ostringstream output;
  string prefix;
  PrometheusWriter writer(&output);
  ASSERT_OK(clock_extrapolating->WriteAsPrometheus(&writer, prefix));

  const string expected_output = "# HELP test_gauge_bool Description of Test boolean Gauge\n"
                                 "# TYPE test_gauge_bool gauge\n"
                                 "test_gauge_bool{unit_type=\"state\"} 0\n";

  ASSERT_EQ(expected_output, output.str());
}

METRIC_DEFINE_gauge_int64(test_entity, test_func_gauge, "Test Function Gauge",
                          MetricUnit::kBytes, "Test Gauge 2",
                          kudu::MetricLevel::kInfo);

static int64_t MyFunction(int* metric_val) {
  return (*metric_val)++;
}

TEST_F(MetricsTest, SimpleFunctionGaugeTest) {
  int metric_val = 1000;
  scoped_refptr<FunctionGauge<int64_t> > gauge =
    METRIC_test_func_gauge.InstantiateFunctionGauge(
        entity_, [&metric_val]() { return MyFunction(&metric_val); });

  ASSERT_EQ(1000, gauge->value());
  ASSERT_EQ(1001, gauge->value());

  gauge->DetachToCurrentValue();
  // After detaching, it should continue to return the same constant value.
  ASSERT_EQ(1002, gauge->value());
  ASSERT_EQ(1002, gauge->value());

  // Test resetting to a constant.
  gauge->DetachToConstant(2);
  ASSERT_EQ(2, gauge->value());
}

METRIC_DEFINE_gauge_int64(test_entity, test_func_gauge_snapshot, "Test Function Gauge snapshot",
                          MetricUnit::kOperations, "Description of Function Gauge snapshot",
                          kudu::MetricLevel::kInfo);
class FunctionGaugeOwner {
 public:
  explicit FunctionGaugeOwner(const scoped_refptr<MetricEntity>& entity) {
    METRIC_test_func_gauge_snapshot.InstantiateFunctionGauge(
        entity, [this]() { return this->Count(); })
        ->AutoDetach(&metric_detacher_);
  }

  int64_t Count() {
    return count_++;
  }

 private:
  int64_t count_ = 0;
  FunctionGaugeDetacher metric_detacher_;
};

TEST_F(MetricsTest, SimpleFunctionGaugeSnapshotTest) {
  std::unique_ptr<FunctionGaugeOwner> fgo(new FunctionGaugeOwner(entity_));
  scoped_refptr<FunctionGauge<int64_t>> old_metric = down_cast<FunctionGauge<int64_t>*>(
    entity_->FindOrNull(METRIC_test_func_gauge_snapshot).get());
  ASSERT_EQ(0, old_metric->value());
  ASSERT_EQ(1, old_metric->value());  // old_metric increased to 2.
  // old_metric increased to 3, and new_metric stay at 2.
  scoped_refptr<FunctionGauge<int64_t>> new_metric =
      down_cast<FunctionGauge<int64_t>*>(old_metric->snapshot().get());
  ASSERT_EQ(3, old_metric->value());
  ASSERT_EQ(4, old_metric->value());
  ASSERT_EQ(2, new_metric->value());
  ASSERT_EQ(2, new_metric->value());
}

TEST_F(MetricsTest, ReleasableFunctionGaugeSnapshotTest) {
  scoped_refptr<FunctionGauge<int64_t>> new_metric;
  {
    std::unique_ptr<FunctionGaugeOwner> fgo(new FunctionGaugeOwner(entity_));
    scoped_refptr<FunctionGauge<int64_t>> old_metric = down_cast<FunctionGauge<int64_t>*>(
      entity_->FindOrNull(METRIC_test_func_gauge_snapshot).get());
    ASSERT_EQ(0, old_metric->value());
    ASSERT_EQ(1, old_metric->value());  // old_metric increased to 2.
    // old_metric increased to 3, and new_metric stay at 2.
    new_metric = down_cast<FunctionGauge<int64_t>*>(old_metric->snapshot().get());
  }
  ASSERT_EQ(2, new_metric->value());
  ASSERT_EQ(2, new_metric->value());
}

TEST_F(MetricsTest, SimpleFunctionGaugeMergeTest) {
  int metric_val = 1000;
  scoped_refptr<FunctionGauge<int64_t> > gauge =
    METRIC_test_func_gauge.InstantiateFunctionGauge(
        entity_, [&metric_val]() { return MyFunction(&metric_val); });

  int metric_val_for_merge = 1234;
  scoped_refptr<FunctionGauge<int64_t> > gauge_for_merge =
    METRIC_test_func_gauge.InstantiateFunctionGauge(
        entity_same_attr_, [&metric_val_for_merge]() {
          return MyFunction(&metric_val_for_merge);
        });

  gauge_for_merge->MergeFrom(gauge);
  ASSERT_EQ(1001, gauge->value());
  ASSERT_EQ(1002, gauge->value());
  ASSERT_EQ(2234, gauge_for_merge->value());
  ASSERT_EQ(2234, gauge_for_merge->value());
  gauge_for_merge->MergeFrom(gauge);
  ASSERT_EQ(3237, gauge_for_merge->value());
  ASSERT_EQ(3237, gauge_for_merge->value());
  gauge_for_merge->MergeFrom(gauge_for_merge);
  ASSERT_EQ(3237, gauge_for_merge->value());
}

TEST_F(MetricsTest, AutoDetachToLastValue) {
  int metric_val = 1000;
  scoped_refptr<FunctionGauge<int64_t> > gauge =
    METRIC_test_func_gauge.InstantiateFunctionGauge(
        entity_, [&metric_val]() { return MyFunction(&metric_val); });

  ASSERT_EQ(1000, gauge->value());
  ASSERT_EQ(1001, gauge->value());
  {
    FunctionGaugeDetacher detacher;
    gauge->AutoDetachToLastValue(&detacher);
    ASSERT_EQ(1002, gauge->value());
    ASSERT_EQ(1003, gauge->value());
  }

  ASSERT_EQ(1004, gauge->value());
  ASSERT_EQ(1004, gauge->value());
}

TEST_F(MetricsTest, AutoDetachToConstant) {
  int metric_val = 1000;
  scoped_refptr<FunctionGauge<int64_t> > gauge =
    METRIC_test_func_gauge.InstantiateFunctionGauge(
        entity_, [&metric_val]() { return MyFunction(&metric_val); });

  ASSERT_EQ(1000, gauge->value());
  ASSERT_EQ(1001, gauge->value());
  {
    FunctionGaugeDetacher detacher;
    gauge->AutoDetach(&detacher, 12345);
    ASSERT_EQ(1002, gauge->value());
    ASSERT_EQ(1003, gauge->value());
  }

  ASSERT_EQ(12345, gauge->value());
}

TEST_F(MetricsTest, FunctionGaugePrometheusTest) {
  int metric_val = 1000;
  scoped_refptr<FunctionGauge<int64_t> > gauge =
    METRIC_test_func_gauge.InstantiateFunctionGauge(
        entity_, [&metric_val]() { return MyFunction(&metric_val); });

  std::ostringstream output;
  string prefix;
  PrometheusWriter writer(&output);
  ASSERT_OK(gauge->WriteAsPrometheus(&writer, prefix));

  const string expected_output = "# HELP test_func_gauge Test Gauge 2\n"
                                 "# TYPE test_func_gauge gauge\n"
                                 "test_func_gauge{unit_type=\"bytes\"} 1000\n";

  ASSERT_EQ(expected_output, output.str());
}

METRIC_DEFINE_gauge_uint64(test_entity, counter_as_gauge, "Gauge exposed as Counter",
                           MetricUnit::kBytes, "Gauge exposed as Counter",
                           kudu::MetricLevel::kInfo,
                           EXPOSE_AS_COUNTER);
TEST_F(MetricsTest, TEstExposeGaugeAsCounter) {
  ASSERT_EQ(MetricType::kCounter, METRIC_counter_as_gauge.type());
}

METRIC_DEFINE_histogram(test_entity, test_hist, "Test Histogram",
                        MetricUnit::kMilliseconds, "foo",
                        MetricLevel::kInfo,
                        1000000, 3);

TEST_F(MetricsTest, SimpleHistogramTest) {
  scoped_refptr<Histogram> hist = METRIC_test_hist.Instantiate(entity_);
  hist->Increment(2);
  hist->IncrementBy(4, 1);
  ASSERT_EQ(2, hist->histogram()->MinValue());
  ASSERT_EQ(3, hist->histogram()->MeanValue());
  ASSERT_EQ(4, hist->histogram()->MaxValue());
  ASSERT_EQ(2, hist->histogram()->TotalCount());
  ASSERT_EQ(6, hist->histogram()->TotalSum());
  // TODO(someone): Test coverage needs to be improved a lot.
}

TEST_F(MetricsTest, SimpleHistogramMergeTest) {
  scoped_refptr<Histogram> hist = METRIC_test_hist.Instantiate(entity_);
  scoped_refptr<Histogram> hist_for_merge = METRIC_test_hist.Instantiate(entity_same_attr_);
  hist->Increment(2);
  hist->IncrementBy(6, 1);
  hist_for_merge->Increment(1);
  hist_for_merge->IncrementBy(3, 3);
  hist_for_merge->MergeFrom(hist);
  ASSERT_EQ(2, hist->histogram()->MinValue());
  ASSERT_EQ(4, hist->histogram()->MeanValue());
  ASSERT_EQ(6, hist->histogram()->MaxValue());
  ASSERT_EQ(2, hist->histogram()->TotalCount());
  ASSERT_EQ(8, hist->histogram()->TotalSum());
  ASSERT_EQ(1, hist_for_merge->histogram()->MinValue());
  ASSERT_EQ(3, hist_for_merge->histogram()->MeanValue());
  ASSERT_EQ(6, hist_for_merge->histogram()->MaxValue());
  ASSERT_EQ(6, hist_for_merge->histogram()->TotalCount());
  ASSERT_EQ(18, hist_for_merge->histogram()->TotalSum());
  ASSERT_EQ(1, hist_for_merge->histogram()->ValueAtPercentile(20.0));
  ASSERT_EQ(2, hist_for_merge->histogram()->ValueAtPercentile(30.0));
  ASSERT_EQ(3, hist_for_merge->histogram()->ValueAtPercentile(50.0));
  ASSERT_EQ(3, hist_for_merge->histogram()->ValueAtPercentile(90.0));
  ASSERT_EQ(6, hist_for_merge->histogram()->ValueAtPercentile(100.0));
  hist_for_merge->MergeFrom(hist_for_merge);
  ASSERT_EQ(6, hist_for_merge->histogram()->TotalCount());
  ASSERT_EQ(18, hist_for_merge->histogram()->TotalSum());
}

TEST_F(MetricsTest, HistogramPrometheusTest) {
  scoped_refptr<Histogram> hist = METRIC_test_hist.Instantiate(entity_);

  std::ostringstream output;
  PrometheusWriter writer(&output);
  string prefix;
  ASSERT_OK(hist->WriteAsPrometheus(&writer, prefix));

  const string expected_output = "# HELP test_hist foo\n"
                                 "# TYPE test_hist histogram\n"
                                 "test_hist_bucket{unit_type=\"milliseconds\", le=\"0.75\"} 0\n"
                                 "test_hist_bucket{unit_type=\"milliseconds\", le=\"0.95\"} 0\n"
                                 "test_hist_bucket{unit_type=\"milliseconds\", le=\"0.99\"} 0\n"
                                 "test_hist_bucket{unit_type=\"milliseconds\", le=\"0.999\"} 0\n"
                                 "test_hist_bucket{unit_type=\"milliseconds\", le=\"0.9999\"} 0\n"
                                 "test_hist_bucket{unit_type=\"milliseconds\", le=\"+Inf\"} 0\n"
                                 "test_hist_sum{unit_type=\"milliseconds\"} 0\n"
                                 "test_hist_count{unit_type=\"milliseconds\"} 0\n";

  ASSERT_EQ(expected_output, output.str());
}

TEST_F(MetricsTest, JsonPrintTest) {
  scoped_refptr<Counter> test_counter = METRIC_test_counter.Instantiate(entity_);
  test_counter->Increment();
  scoped_refptr<AtomicGauge<uint64_t>> test_gauge = METRIC_test_gauge.Instantiate(entity_, 0);
  test_gauge->IncrementBy(2);
  entity_->SetAttribute("test_attr", "attr_val");

  // Generate the JSON.
  std::ostringstream out;
  JsonWriter writer(&out, JsonWriter::PRETTY);
  ASSERT_OK(entity_->WriteAsJson(&writer, MetricJsonOptions()));

  // Now parse it back out.
  JsonReader reader(out.str());
  ASSERT_OK(reader.Init());

  vector<const rapidjson::Value*> metrics;
  ASSERT_OK(reader.ExtractObjectArray(reader.root(), "metrics", &metrics));
  ASSERT_EQ(2, metrics.size());

  // Mapping metric_name-->metric_value
  unordered_map<string, int64_t> metric_map;
  string metric_name;
  int64_t metric_value;
  ASSERT_OK(reader.ExtractString(metrics[0], "name", &metric_name));
  ASSERT_OK(reader.ExtractInt64(metrics[0], "value", &metric_value));
  InsertOrDie(&metric_map, metric_name, metric_value);
  ASSERT_OK(reader.ExtractString(metrics[1], "name", &metric_name));
  ASSERT_OK(reader.ExtractInt64(metrics[1], "value", &metric_value));
  InsertOrDie(&metric_map, metric_name, metric_value);

  ASSERT_TRUE(ContainsKey(metric_map, "test_counter"));
  ASSERT_EQ(1L, metric_map["test_counter"]);
  ASSERT_TRUE(ContainsKey(metric_map, "test_gauge"));
  ASSERT_EQ(2L, metric_map["test_gauge"]);

  const rapidjson::Value* attributes;
  ASSERT_OK(reader.ExtractObject(reader.root(), "attributes", &attributes));
  string attr_value;
  ASSERT_OK(reader.ExtractString(attributes, "test_attr", &attr_value));
  ASSERT_EQ("attr_val", attr_value);

  // Verify that metric filtering matches on substrings.
  {
    out.str("");
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts;
    opts.filters.entity_metrics.emplace_back("test_count");
    ASSERT_OK(entity_->WriteAsJson(&writer, opts));
    ASSERT_STR_CONTAINS(out.str(), METRIC_test_counter.name());
    ASSERT_STR_NOT_CONTAINS(out.str(), METRIC_test_gauge.name());
  }

  // Verify that, if we filter for a metric that isn't in this entity, we get no result.
  {
    out.str("");
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts;
    opts.filters.entity_metrics.emplace_back("not_a_matching_metric");
    ASSERT_OK(entity_->WriteAsJson(&writer, opts));
    ASSERT_EQ(out.str(), "");
  }

  // Verify that filtering is case-insensitive.
  {
    out.str("");
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts;
    opts.filters.entity_metrics.emplace_back("teST_coUNteR");
    ASSERT_OK(entity_->WriteAsJson(&writer, opts));
    ASSERT_STR_CONTAINS(out.str(), METRIC_test_counter.name());
    ASSERT_STR_NOT_CONTAINS(out.str(), METRIC_test_gauge.name());
  }
}

// Check JSON style 'output' whether match 'expect_counters'.
void CheckMergeOutput(const std::ostringstream& output,
                      std::map<std::string, int> expect_counters) {
  JsonReader reader(output.str());
  ASSERT_OK(reader.Init());

  vector<const rapidjson::Value*> counters;
  ASSERT_OK(reader.ExtractObjectArray(reader.root(), nullptr, &counters));
  ASSERT_EQ(expect_counters.size(), counters.size());
  for (const auto& counter : counters) {
    string type;
    ASSERT_OK(reader.ExtractString(counter, "type", &type));
    ASSERT_EQ("merged_entity", type);
    string id;
    ASSERT_OK(reader.ExtractString(counter, "id", &id));
    auto it = expect_counters.find(id);
    ASSERT_NE(it, expect_counters.end());
    vector<const rapidjson::Value*> metrics;
    ASSERT_OK(reader.ExtractObjectArray(counter, "metrics", &metrics));
    string metric_name;
    ASSERT_OK(reader.ExtractString(metrics[0], "name", &metric_name));
    ASSERT_EQ("test_counter", metric_name);
    int64_t metric_value;
    ASSERT_OK(reader.ExtractInt64(metrics[0], "value", &metric_value));
    ASSERT_EQ(it->second, metric_value);
    expect_counters.erase(it);
  }
  ASSERT_TRUE(expect_counters.empty());
}

TEST_F(MetricsTest, CollectTest) {
  scoped_refptr<Counter> test_counter = METRIC_test_counter.Instantiate(entity_);
  test_counter->Increment();

  scoped_refptr<Counter> test_counter_same_attr =
      METRIC_test_counter.Instantiate(entity_same_attr_);
  test_counter_same_attr->IncrementBy(10);

  scoped_refptr<Counter> test_counter_diff_attr =
      METRIC_test_counter.Instantiate(entity_diff_attr_);
  test_counter_diff_attr->IncrementBy(100);

  MetricJsonOptions base_opts;
  base_opts.merge_rules.emplace(
      "test_entity",
      MergeAttributes("merged_entity", "attr_for_merge"));

  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    ASSERT_OK(registry_.WriteAsJson(&writer, base_opts));
    NO_FATALS(CheckMergeOutput(out, {{"same_attr", 11},
                                     {"diff_attr", 100}}));
  }

  // Verify that metric filtering matches on substrings.
  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts(base_opts);
    opts.filters.entity_metrics.emplace_back("counter");
    ASSERT_OK(registry_.WriteAsJson(&writer, opts));
    NO_FATALS(CheckMergeOutput(out, {{"same_attr", 11},
                                     {"diff_attr", 100}}));
  }

  // Verify that, if we filter for a metric that isn't in this entity, we get no result.
  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts(base_opts);
    opts.filters.entity_metrics.emplace_back("not_a_matching_metric");
    ASSERT_OK(registry_.WriteAsJson(&writer, opts));
    NO_FATALS(CheckMergeOutput(out, {}));
  }

  // Verify that metric entity id filtering matches on substrings.
  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts(base_opts);
    opts.filters.entity_ids.emplace_back("my-test-same-attr");
    ASSERT_OK(registry_.WriteAsJson(&writer, opts));
    NO_FATALS(CheckMergeOutput(out, {{"same_attr", 11}}));
  }

  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts(base_opts);
    opts.filters.entity_ids.emplace_back("my-test-same-attr2");
    ASSERT_OK(registry_.WriteAsJson(&writer, opts));
    NO_FATALS(CheckMergeOutput(out, {{"same_attr", 10}}));
  }

  // Verify that, if we filter for a metric entity id that doesn't match any entity,
  // we get no result.
  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts(base_opts);
    opts.filters.entity_ids.emplace_back("not_a_matching_metric_entity_id");
    ASSERT_OK(registry_.WriteAsJson(&writer, opts));
    NO_FATALS(CheckMergeOutput(out, {}));
  }

  // Verify that some attribute filtering matches on substrings.
  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts(base_opts);
    opts.filters.entity_attrs.emplace_back("attr_for_merge");
    opts.filters.entity_attrs.emplace_back("same_attr");
    ASSERT_OK(registry_.WriteAsJson(&writer, opts));
    NO_FATALS(CheckMergeOutput(out, {{"same_attr", 11}}));
  }

  // Verify that, if we filter for an attribute that doesn't match any entity, we get no result.
  {
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::PRETTY);
    MetricJsonOptions opts(base_opts);
    opts.filters.entity_attrs.emplace_back("attr_for_merge");
    opts.filters.entity_attrs.emplace_back("not_a_matching_attr");
    ASSERT_OK(registry_.WriteAsJson(&writer, opts));
    NO_FATALS(CheckMergeOutput(out, {}));
  }
}

// Test that metrics are retired when they are no longer referenced.
TEST_F(MetricsTest, RetirementTest) {
  FLAGS_metrics_retirement_age_ms = 100;

  const string kMetricName = "foo";
  scoped_refptr<Counter> counter = METRIC_test_counter.Instantiate(entity_);
  ASSERT_EQ(1, entity_->UnsafeMetricsMapForTests().size());

  // Since we hold a reference to the counter, it should not get retired.
  entity_->RetireOldMetrics();
  ASSERT_EQ(1, entity_->UnsafeMetricsMapForTests().size());

  // When we de-ref it, it should not get immediately retired, either, because
  // we keep retirable metrics around for some amount of time. We try retiring
  // a number of times to hit all the cases.
  counter = nullptr;
  for (int i = 0; i < 3; i++) {
    entity_->RetireOldMetrics();
    ASSERT_EQ(1, entity_->UnsafeMetricsMapForTests().size());
  }

  // If we wait for longer than the retirement time, and call retire again, we'll
  // actually retire it.
  SleepFor(MonoDelta::FromMilliseconds(FLAGS_metrics_retirement_age_ms * 1.5));
  entity_->RetireOldMetrics();
  ASSERT_EQ(0, entity_->UnsafeMetricsMapForTests().size());
}

TEST_F(MetricsTest, TestRetiringEntities) {
  ASSERT_EQ(kEntityCount, registry_.num_entities());

  // Drop the reference to our entity.
  entity_.reset();
  entity_same_attr_.reset();
  entity_diff_attr_.reset();

  // Retire metrics. Since there is nothing inside our entity, it should
  // retire immediately (no need to loop).
  registry_.RetireOldMetrics();

  ASSERT_EQ(0, registry_.num_entities());
}

// Test that we can mark a metric to never be retired.
TEST_F(MetricsTest, NeverRetireTest) {
  entity_->NeverRetire(METRIC_test_hist.Instantiate(entity_));
  FLAGS_metrics_retirement_age_ms = 0;

  for (int i = 0; i < 3; i++) {
    entity_->RetireOldMetrics();
    ASSERT_EQ(1, entity_->UnsafeMetricsMapForTests().size());
  }
}

TEST_F(MetricsTest, TestInstantiatingTwice) {
  // Test that re-instantiating the same entity ID returns the same object.
  scoped_refptr<MetricEntity> new_entity = METRIC_ENTITY_test_entity.Instantiate(
      &registry_, entity_->id());
  ASSERT_EQ(new_entity.get(), entity_.get());
}

TEST_F(MetricsTest, TestInstantiatingDifferentEntities) {
  scoped_refptr<MetricEntity> new_entity = METRIC_ENTITY_test_entity.Instantiate(
      &registry_, "some other ID");
  ASSERT_NE(new_entity.get(), entity_.get());
}

TEST_F(MetricsTest, TestDumpJsonPrototypes) {
  // Dump the prototype info.
  std::ostringstream out;
  JsonWriter w(&out, JsonWriter::PRETTY);
  MetricPrototypeRegistry::get()->WriteAsJson(&w);
  string json = out.str();

  // Quick sanity check for one of our metrics defined in this file.
  const char* expected =
    "        {\n"
    "            \"name\": \"test_func_gauge\",\n"
    "            \"label\": \"Test Function Gauge\",\n"
    "            \"type\": \"gauge\",\n"
    "            \"unit\": \"bytes\",\n"
    "            \"description\": \"Test Gauge 2\",\n"
    "            \"level\": \"info\",\n"
    "            \"entity_type\": \"test_entity\"\n"
    "        }";
  ASSERT_STR_CONTAINS(json, expected);

  // Parse it.
  rapidjson::Document d;
  d.Parse<0>(json.c_str());

  // Ensure that we got a reasonable number of metrics.
  int num_metrics = d["metrics"].Size();
  int num_entities = d["entities"].Size();
  LOG(INFO) << "Parsed " << num_metrics << " metrics and " << num_entities << " entities";
  ASSERT_GT(num_metrics, 5);
  ASSERT_EQ(num_entities, 2);

  // Spot-check that some metrics were properly registered and that the JSON was properly
  // formed.
  unordered_set<string> seen_metrics;
  for (int i = 0; i < d["metrics"].Size(); i++) {
    InsertOrDie(&seen_metrics, d["metrics"][i]["name"].GetString());
  }
  ASSERT_TRUE(ContainsKey(seen_metrics, "threads_started"));
  ASSERT_TRUE(ContainsKey(seen_metrics, "test_hist"));
}

TEST_F(MetricsTest, TestDumpOnlyChanged) {
  auto GetJson = [&](int64_t since_epoch) {
    MetricJsonOptions opts;
    opts.only_modified_in_or_after_epoch = since_epoch;
    std::ostringstream out;
    JsonWriter writer(&out, JsonWriter::COMPACT);
    CHECK_OK(entity_->WriteAsJson(&writer, opts));
    return out.str();
  };

  scoped_refptr<Counter> test_counter = METRIC_test_counter.Instantiate(entity_);
  test_counter->InvalidateEpoch();

  // It's not visible before it changed.
  int64_t epoch_before_modified = Metric::current_epoch();
  ASSERT_STR_NOT_CONTAINS(GetJson(epoch_before_modified), "test_counter");

  // Increment() will make it visible.
  test_counter->Increment();

  // If we pass a "since dirty" epoch from before we incremented it, we should
  // see the metric.
  for (int i = 0; i < 2; i++) {
    ASSERT_STR_CONTAINS(GetJson(epoch_before_modified), "{\"name\":\"test_counter\",\"value\":1}");
    Metric::IncrementEpoch();
  }

  // If we pass a current epoch, we should see that the metric was not modified.
  int64_t new_epoch = Metric::current_epoch();
  ASSERT_STR_NOT_CONTAINS(GetJson(new_epoch), "test_counter");
  // ... until we modify it again.
  test_counter->Increment();
  ASSERT_STR_CONTAINS(GetJson(new_epoch), "{\"name\":\"test_counter\",\"value\":2}");
}

// Test that 'include_untouched_metrics=false' prevents dumping counters and histograms
// which have never been incremented.
TEST_F(MetricsTest, TestDontDumpUntouched) {
  // Instantiate a bunch of metrics.
  int metric_val = 1000;
  scoped_refptr<Counter> test_counter = METRIC_test_counter.Instantiate(entity_);
  scoped_refptr<Histogram> hist = METRIC_test_hist.Instantiate(entity_);
  scoped_refptr<FunctionGauge<int64_t> > function_gauge =
    METRIC_test_func_gauge.InstantiateFunctionGauge(
        entity_, [&metric_val]() { return MyFunction(&metric_val); });
  scoped_refptr<AtomicGauge<uint64_t> > atomic_gauge =
    METRIC_test_gauge.Instantiate(entity_, 0);

  MetricJsonOptions opts;
  opts.include_untouched_metrics = false;
  std::ostringstream out;
  JsonWriter writer(&out, JsonWriter::COMPACT);
  CHECK_OK(entity_->WriteAsJson(&writer, opts));
  // Untouched counters and histograms should not be included.
  ASSERT_STR_NOT_CONTAINS(out.str(), "test_counter");
  ASSERT_STR_NOT_CONTAINS(out.str(), "test_hist");
  // Untouched gauges need to be included, because we don't actually
  // track whether they have been touched.
  ASSERT_STR_CONTAINS(out.str(), "test_func_gauge");
  ASSERT_STR_CONTAINS(out.str(), "test_gauge");
}

METRIC_DEFINE_counter(test_entity, warn_counter, "Warn Metric", MetricUnit::kRequests,
                      "Description of warn metric",
                      kudu::MetricLevel::kWarn);

METRIC_DEFINE_counter(test_entity, debug_counter, "Debug Metric", MetricUnit::kRequests,
                      "Description of debug metric",
                      kudu::MetricLevel::kDebug);

TEST_F(MetricsTest, TestFilter) {
  const int32_t kNum = 4;
  vector<string> id_uuids;
  const string attr1 = "attr1";
  const string attr2 = "attr2";
  vector<string> attr1_uuids;
  vector<string> attr2_uuids;

  // 1.Generate metrics.
  ObjectIdGenerator oid;
  for (int i = 0; i < kNum; ++i) {
    string id_uuid = oid.Next();
    string attr1_uuid = oid.Next();
    string attr2_uuid = oid.Next();

    MetricEntity::AttributeMap attrs;
    attrs[attr1] = attr1_uuid;
    attrs[attr2] = attr2_uuid;
    scoped_refptr<MetricEntity> entity =
        METRIC_ENTITY_test_entity.Instantiate(&registry_, id_uuid, attrs);
    scoped_refptr<Counter> metric1 = METRIC_test_counter.Instantiate(entity);
    scoped_refptr<AtomicGauge<uint64_t>> metric2 = METRIC_test_gauge.Instantiate(entity, 0);

    id_uuids.emplace_back(id_uuid);
    attr1_uuids.emplace_back(attr1_uuid);
    attr2_uuids.emplace_back(attr2_uuid);
  }

  // Add 1 warn and 1 debug entity and metric.
  scoped_refptr<MetricEntity> warnEntity =
      METRIC_ENTITY_test_entity.Instantiate(&registry_, oid.Next());
  scoped_refptr<Counter> warnMetric = METRIC_warn_counter.Instantiate(warnEntity);
  scoped_refptr<MetricEntity> debugEntity =
      METRIC_ENTITY_test_entity.Instantiate(&registry_, oid.Next());
  scoped_refptr<Counter> debugMetric = METRIC_debug_counter.Instantiate(debugEntity);

  // 2.Check the filter.
  Random rand(SeedRandom());
  const string not_exist_string = "not_exist_string";

  // 2.1 Filter the 'type'.
  {
    {
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_types = { not_exist_string };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      ASSERT_EQ("[]", out.str());
    }
    {
      const string entity_type = "test_entity";
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_types = { entity_type };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      rapidjson::Document d;
      d.Parse<0>(out.str().c_str());
      ASSERT_EQ(kNum + kEntityCount + 2, d.Size());
      ASSERT_EQ(entity_type, d[rand.Next() % kNum]["type"].GetString());
    }
  }
  // 2.2 Filter the 'id'.
  {
    {
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_ids = { not_exist_string };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      ASSERT_EQ("[]", out.str());
    }
    {
      const string& entity_id = id_uuids[rand.Next() % kNum];
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_ids = { entity_id };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      rapidjson::Document d;
      d.Parse<0>(out.str().c_str());
      ASSERT_EQ(1, d.Size());
      ASSERT_EQ(entity_id, d[0]["id"].GetString());
    }
  }
  // 2.3 Filter the 'attributes'.
  {
    {
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_attrs = { attr1, not_exist_string };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      ASSERT_EQ("[]", out.str());
    }
    {
      int i = rand.Next() % kNum;
      const string& attr1_uuid = attr1_uuids[i];
      const string& attr2_uuid = attr2_uuids[i];
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_attrs = { attr1, attr1_uuid };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      rapidjson::Document d;
      d.Parse<0>(out.str().c_str());
      ASSERT_EQ(1, d.Size());
      ASSERT_EQ(attr1_uuid, d[0]["attributes"]["attr1"].GetString());
      ASSERT_EQ(attr2_uuid, d[0]["attributes"]["attr2"].GetString());
    }
  }
  // 2.4 Filter the 'metrics'.
  {
    {
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_metrics = { not_exist_string };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      ASSERT_EQ("[]", out.str());
    }
    {
      const string entity_metric1 = "test_counter";
      const string entity_metric2 = "test_gauge";
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_metrics = { entity_metric1 };
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      ASSERT_STR_CONTAINS(out.str(), entity_metric1);
      ASSERT_STR_NOT_CONTAINS(out.str(), entity_metric2);
      rapidjson::Document d;
      d.Parse<0>(out.str().c_str());
      ASSERT_EQ(kNum, d.Size());
    }
  }
  // 2.5 Filter the 'level'
  {
    // Higher level.
    {
      const string entity_level = "warn";
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_level = entity_level;
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      rapidjson::Document d;
      d.Parse<0>(out.str().c_str());
      ASSERT_EQ(kEntityCount + 1, d.Size());
    }
    // Debug level includes info and warn level.
    {
      const string entity_level = "debug";
      std::ostringstream out;
      MetricJsonOptions opts;
      opts.filters.entity_level = entity_level;
      JsonWriter w(&out, JsonWriter::PRETTY);
      ASSERT_OK(registry_.WriteAsJson(&w, opts));
      rapidjson::Document d;
      d.Parse<0>(out.str().c_str());
      ASSERT_EQ(kNum + kEntityCount + 2, d.Size());
    }
  }

  // 2.6 Default filter condition.
  {
    std::ostringstream out;
    JsonWriter w(&out, JsonWriter::PRETTY);
    ASSERT_OK(registry_.WriteAsJson(&w, MetricJsonOptions()));
    rapidjson::Document d;
    d.Parse<0>(out.str().c_str());
    ASSERT_EQ(kNum + kEntityCount + 2, d.Size());
  }
}

} // namespace kudu