base/metrics/statistics_recorder.cc

// Copyright (c) 2012 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/statistics_recorder.h"

#include "base/at_exit.h"
#include "base/json/string_escape.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/metrics/histogram.h"
#include "base/metrics/metrics_hashes.h"
#include "base/stl_util.h"
#include "base/strings/stringprintf.h"
#include "base/synchronization/lock.h"
#include "base/values.h"

namespace {
// Initialize histogram statistics gathering system.
base::LazyInstance<base::StatisticsRecorder>::Leaky g_statistics_recorder_ =
    LAZY_INSTANCE_INITIALIZER;
}  // namespace

namespace base {

// static
void StatisticsRecorder::Initialize() {
  // Ensure that an instance of the StatisticsRecorder object is created.
  g_statistics_recorder_.Get();
}

// static
bool StatisticsRecorder::IsActive() {
  if (lock_ == NULL)
    return false;
  base::AutoLock auto_lock(*lock_);
  return NULL != histograms_;
}

// static
HistogramBase* StatisticsRecorder::RegisterOrDeleteDuplicate(
    HistogramBase* histogram) {
  // As per crbug.com/79322 the histograms are intentionally leaked.
  if (lock_ == NULL) {
    return histogram;
  }

  HistogramBase* histogram_to_delete = NULL;
  HistogramBase* histogram_to_return = NULL;
  {
    base::AutoLock auto_lock(*lock_);
    if (histograms_ == NULL) {
      histogram_to_return = histogram;
    } else {
      const std::string& name = histogram->histogram_name();
      uint64_t name_hash = histogram->name_hash();
      HistogramMap::iterator it = histograms_->find(name_hash);
      if (histograms_->end() == it) {
        (*histograms_)[name_hash] = histogram;
        // If there are callbacks for this histogram, we set the kCallbackExists
        // flag.
        auto callback_iterator = callbacks_->find(name);
        if (callback_iterator != callbacks_->end()) {
          if (!callback_iterator->second.is_null())
            histogram->SetFlags(HistogramBase::kCallbackExists);
          else
            histogram->ClearFlags(HistogramBase::kCallbackExists);
        }
        histogram_to_return = histogram;
      } else if (histogram == it->second) {
        // The histogram was registered before.
        histogram_to_return = histogram;
      } else {
        // We already have one histogram with this name.
        DCHECK_EQ(histogram->histogram_name(),
                  it->second->histogram_name()) << "hash collision";
        histogram_to_return = it->second;
        histogram_to_delete = histogram;
      }
    }
  }
  delete histogram_to_delete;
  return histogram_to_return;
}

// static
const BucketRanges* StatisticsRecorder::RegisterOrDeleteDuplicateRanges(
    const BucketRanges* ranges) {
  DCHECK(ranges->HasValidChecksum());
  scoped_ptr<const BucketRanges> ranges_deleter;

  if (lock_ == NULL) {
    return ranges;
  }

  base::AutoLock auto_lock(*lock_);
  if (ranges_ == NULL) {
    return ranges;
  }

  std::list<const BucketRanges*>* checksum_matching_list;
  RangesMap::iterator ranges_it = ranges_->find(ranges->checksum());
  if (ranges_->end() == ranges_it) {
    // Add a new matching list to map.
    checksum_matching_list = new std::list<const BucketRanges*>();
    (*ranges_)[ranges->checksum()] = checksum_matching_list;
  } else {
    checksum_matching_list = ranges_it->second;
  }

  for (const BucketRanges* existing_ranges : *checksum_matching_list) {
    if (existing_ranges->Equals(ranges)) {
      if (existing_ranges == ranges) {
        return ranges;
      } else {
        ranges_deleter.reset(ranges);
        return existing_ranges;
      }
    }
  }
  // We haven't found a BucketRanges which has the same ranges. Register the
  // new BucketRanges.
  checksum_matching_list->push_front(ranges);
  return ranges;
}

// static
void StatisticsRecorder::WriteHTMLGraph(const std::string& query,
                                        std::string* output) {
  if (!IsActive())
    return;

  Histograms snapshot;
  GetSnapshot(query, &snapshot);
  for (const HistogramBase* histogram : snapshot) {
    histogram->WriteHTMLGraph(output);
    output->append("<br><hr><br>");
  }
}

// static
void StatisticsRecorder::WriteGraph(const std::string& query,
                                    std::string* output) {
  if (!IsActive())
    return;
  if (query.length())
    StringAppendF(output, "Collections of histograms for %s\n", query.c_str());
  else
    output->append("Collections of all histograms\n");

  Histograms snapshot;
  GetSnapshot(query, &snapshot);
  for (const HistogramBase* histogram : snapshot) {
    histogram->WriteAscii(output);
    output->append("\n");
  }
}

// static
std::string StatisticsRecorder::ToJSON(const std::string& query) {
  if (!IsActive())
    return std::string();

  std::string output("{");
  if (!query.empty()) {
    output += "\"query\":";
    EscapeJSONString(query, true, &output);
    output += ",";
  }

  Histograms snapshot;
  GetSnapshot(query, &snapshot);
  output += "\"histograms\":[";
  bool first_histogram = true;
  for (const HistogramBase* histogram : snapshot) {
    if (first_histogram)
      first_histogram = false;
    else
      output += ",";
    std::string json;
    histogram->WriteJSON(&json);
    output += json;
  }
  output += "]}";
  return output;
}

// static
void StatisticsRecorder::GetHistograms(Histograms* output) {
  if (lock_ == NULL)
    return;
  base::AutoLock auto_lock(*lock_);
  if (histograms_ == NULL)
    return;

  for (const auto& entry : *histograms_) {
    DCHECK_EQ(entry.first, entry.second->name_hash());
    output->push_back(entry.second);
  }
}

// static
void StatisticsRecorder::GetBucketRanges(
    std::vector<const BucketRanges*>* output) {
  if (lock_ == NULL)
    return;
  base::AutoLock auto_lock(*lock_);
  if (ranges_ == NULL)
    return;

  for (const auto& entry : *ranges_) {
    for (const auto& range_entry : *entry.second) {
      output->push_back(range_entry);
    }
  }
}

// static
HistogramBase* StatisticsRecorder::FindHistogram(const std::string& name) {
  if (lock_ == NULL)
    return NULL;
  base::AutoLock auto_lock(*lock_);
  if (histograms_ == NULL)
    return NULL;

  HistogramMap::iterator it = histograms_->find(HashMetricName(name));
  if (histograms_->end() == it)
    return NULL;
  DCHECK_EQ(name, it->second->histogram_name()) << "hash collision";
  return it->second;
}

// static
bool StatisticsRecorder::SetCallback(
    const std::string& name,
    const StatisticsRecorder::OnSampleCallback& cb) {
  DCHECK(!cb.is_null());
  if (lock_ == NULL)
    return false;
  base::AutoLock auto_lock(*lock_);
  if (histograms_ == NULL)
    return false;

  if (ContainsKey(*callbacks_, name))
    return false;
  callbacks_->insert(std::make_pair(name, cb));

  HistogramMap::iterator it = histograms_->find(HashMetricName(name));
  if (it != histograms_->end()) {
    DCHECK_EQ(name, it->second->histogram_name()) << "hash collision";
    it->second->SetFlags(HistogramBase::kCallbackExists);
  }

  return true;
}

// static
void StatisticsRecorder::ClearCallback(const std::string& name) {
  if (lock_ == NULL)
    return;
  base::AutoLock auto_lock(*lock_);
  if (histograms_ == NULL)
    return;

  callbacks_->erase(name);

  // We also clear the flag from the histogram (if it exists).
  HistogramMap::iterator it = histograms_->find(HashMetricName(name));
  if (it != histograms_->end()) {
    DCHECK_EQ(name, it->second->histogram_name()) << "hash collision";
    it->second->ClearFlags(HistogramBase::kCallbackExists);
  }
}

// static
StatisticsRecorder::OnSampleCallback StatisticsRecorder::FindCallback(
    const std::string& name) {
  if (lock_ == NULL)
    return OnSampleCallback();
  base::AutoLock auto_lock(*lock_);
  if (histograms_ == NULL)
    return OnSampleCallback();

  auto callback_iterator = callbacks_->find(name);
  return callback_iterator != callbacks_->end() ? callback_iterator->second
                                                : OnSampleCallback();
}

// private static
void StatisticsRecorder::GetSnapshot(const std::string& query,
                                     Histograms* snapshot) {
  if (lock_ == NULL)
    return;
  base::AutoLock auto_lock(*lock_);
  if (histograms_ == NULL)
    return;

  for (const auto& entry : *histograms_) {
    if (entry.second->histogram_name().find(query) != std::string::npos)
      snapshot->push_back(entry.second);
  }
}

// This singleton instance should be started during the single threaded portion
// of main(), and hence it is not thread safe.  It initializes globals to
// provide support for all future calls.
StatisticsRecorder::StatisticsRecorder() {
  DCHECK(!histograms_);
  if (lock_ == NULL) {
    // This will leak on purpose. It's the only way to make sure we won't race
    // against the static uninitialization of the module while one of our
    // static methods relying on the lock get called at an inappropriate time
    // during the termination phase. Since it's a static data member, we will
    // leak one per process, which would be similar to the instance allocated
    // during static initialization and released only on  process termination.
    lock_ = new base::Lock;
  }
  base::AutoLock auto_lock(*lock_);
  histograms_ = new HistogramMap;
  callbacks_ = new CallbackMap;
  ranges_ = new RangesMap;

  if (VLOG_IS_ON(1))
    AtExitManager::RegisterCallback(&DumpHistogramsToVlog, this);
}

// static
void StatisticsRecorder::DumpHistogramsToVlog(void* /* instance */) {
  std::string output;
  StatisticsRecorder::WriteGraph(std::string(), &output);
  VLOG(1) << output;
}

StatisticsRecorder::~StatisticsRecorder() {
  DCHECK(histograms_ && ranges_ && lock_);

  // Clean up.
  scoped_ptr<HistogramMap> histograms_deleter;
  scoped_ptr<CallbackMap> callbacks_deleter;
  scoped_ptr<RangesMap> ranges_deleter;
  // We don't delete lock_ on purpose to avoid having to properly protect
  // against it going away after we checked for NULL in the static methods.
  {
    base::AutoLock auto_lock(*lock_);
    histograms_deleter.reset(histograms_);
    callbacks_deleter.reset(callbacks_);
    ranges_deleter.reset(ranges_);
    histograms_ = NULL;
    callbacks_ = NULL;
    ranges_ = NULL;
  }
  // We are going to leak the histograms and the ranges.
}


// static
StatisticsRecorder::HistogramMap* StatisticsRecorder::histograms_ = NULL;
// static
StatisticsRecorder::CallbackMap* StatisticsRecorder::callbacks_ = NULL;
// static
StatisticsRecorder::RangesMap* StatisticsRecorder::ranges_ = NULL;
// static
base::Lock* StatisticsRecorder::lock_ = NULL;

}  // namespace base