chrome/browser/metrics/subprocess_metrics_provider.h

// Copyright 2016 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.

#ifndef CHROME_BROWSER_METRICS_SUBPROCESS_METRICS_PROVIDER_H_
#define CHROME_BROWSER_METRICS_SUBPROCESS_METRICS_PROVIDER_H_

#include <memory>
#include <set>

#include "base/gtest_prod_util.h"
#include "base/id_map.h"
#include "base/scoped_observer.h"
#include "base/threading/thread_checker.h"
#include "components/metrics/metrics_provider.h"
#include "content/public/browser/notification_observer.h"
#include "content/public/browser/notification_registrar.h"
#include "content/public/browser/render_process_host_observer.h"

namespace base {
class PersistentHistogramAllocator;
class SharedPersistentMemoryAllocator;
}

// SubprocessMetricsProvider gathers and merges histograms stored in shared
// memory segments between processes. Merging occurs when a process exits,
// when metrics are being collected for upload, or when something else needs
// combined metrics (such as the chrome://histograms page).
class SubprocessMetricsProvider : public metrics::MetricsProvider,
                                  public content::NotificationObserver,
                                  public content::RenderProcessHostObserver {
 public:
  SubprocessMetricsProvider();
  ~SubprocessMetricsProvider() override;

 private:
  friend class SubprocessMetricsProviderTest;

  // Indicates subprocess to be monitored with unique id for later reference.
  // Metrics reporting will read histograms from it and upload them to UMA.
  void RegisterSubprocessAllocator(
      int id,
      std::unique_ptr<base::PersistentHistogramAllocator> allocator);

  // Indicates that a subprocess has exited and is thus finished with the
  // allocator it was using.
  void DeregisterSubprocessAllocator(int id);

  // Merge all histograms of a given allocator to the global StatisticsRecorder.
  // This is called periodically during UMA metrics collection (if enabled) and
  // possibly on-demand for other purposes.
  void MergeHistogramDeltasFromAllocator(
      int id,
      base::PersistentHistogramAllocator* allocator);

  // metrics::MetricsProvider:
  void MergeHistogramDeltas() override;

  // content::NotificationObserver:
  void Observe(int type,
               const content::NotificationSource& source,
               const content::NotificationDetails& details) override;

  // content::RenderProcessHostObserver:
  void RenderProcessReady(content::RenderProcessHost* host) override;
  void RenderProcessExited(content::RenderProcessHost* host,
                           base::TerminationStatus status,
                           int exit_code) override;
  void RenderProcessHostDestroyed(content::RenderProcessHost* host) override;

  base::ThreadChecker thread_checker_;

  // Object for registing notification requests.
  content::NotificationRegistrar registrar_;

  // All of the shared-persistent-allocators for known sub-processes.
  using AllocatorByIdMap =
      IDMap<base::PersistentHistogramAllocator, IDMapOwnPointer, int>;
  AllocatorByIdMap allocators_by_id_;

  // Track all observed render processes to un-observe them on exit.
  ScopedObserver<content::RenderProcessHost, SubprocessMetricsProvider>
      scoped_observer_;

  DISALLOW_COPY_AND_ASSIGN(SubprocessMetricsProvider);
};

#endif  // CHROME_BROWSER_METRICS_SUBPROCESS_METRICS_PROVIDER_H_