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// Copyright 2014 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 <memory>
#include <string>
#include "base/callback.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/metrics/field_trial.h"
#include "components/metrics/client_info.h"
class PrefService;
class PrefRegistrySimple;
namespace metrics {
class ClonedInstallDetector;
class EnabledStateProvider;
// Responsible for managing MetricsService state prefs, specifically the UMA
// client id and low entropy source. Code outside the metrics directory should
// not be instantiating or using this class directly.
class MetricsStateManager {
// A callback that can be invoked to store client info to persistent storage.
// Storing an empty client_id will resulted in the backup being voided.
typedef base::Callback<void(const ClientInfo& client_info)>
// A callback that can be invoked to load client info stored through the
// StoreClientInfoCallback.
typedef base::Callback<std::unique_ptr<ClientInfo>(void)>
virtual ~MetricsStateManager();
// Returns true if the user has consented to sending metric reports, and there
// is no other reason to disable reporting. One such reason is client
// sampling, and this client isn't in the sample.
bool IsMetricsReportingEnabled();
// Returns the client ID for this client, or the empty string if the user is
// not opted in to metrics reporting.
const std::string& client_id() const { return client_id_; }
// Forces the client ID to be generated. This is useful in case it's needed
// before recording.
void ForceClientIdCreation();
// Checks if this install was cloned or imaged from another machine. If a
// clone is detected, resets the client id and low entropy source. This
// should not be called more than once.
void CheckForClonedInstall(
scoped_refptr<base::SingleThreadTaskRunner> task_runner);
// Returns the preferred entropy provider used to seed persistent activities
// based on whether or not metrics reporting is permitted on this client.
// If there's consent to report metrics, this method returns an entropy
// provider that has a high source of entropy, partially based on the client
// ID. Otherwise, it returns an entropy provider that is based on a low
// entropy source.
std::unique_ptr<const base::FieldTrial::EntropyProvider>
// Returns an entropy provider that is based on a low entropy source. This
// provider is the same type of provider returned by
// CreateDefaultEntropyProvider when there's no consent to report metrics, but
// will be a new instance.
std::unique_ptr<const base::FieldTrial::EntropyProvider>
// Creates the MetricsStateManager, enforcing that only a single instance
// of the class exists at a time. Returns NULL if an instance exists already.
static std::unique_ptr<MetricsStateManager> Create(
PrefService* local_state,
EnabledStateProvider* enabled_state_provider,
const StoreClientInfoCallback& store_client_info,
const LoadClientInfoCallback& load_client_info);
// Registers local state prefs used by this class.
static void RegisterPrefs(PrefRegistrySimple* registry);
FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, EntropySourceUsed_Low);
FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, EntropySourceUsed_High);
FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, LowEntropySource0NotReset);
FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, ResetMetricsIDs);
// Designates which entropy source was returned from this class.
// This is used for testing to validate that we return the correct source
// depending on the state of the service.
enum EntropySourceType {
// Creates the MetricsStateManager with the given |local_state|. Uses
// |enabled_state_provider| to query whether there is consent for metrics
// reporting, and if it is enabled. Clients should instead use Create(), which
// enforces that a single instance of this class be alive at any given time.
// |store_client_info| should back up client info to persistent storage such
// that it is later retrievable by |load_client_info|.
MetricsStateManager(PrefService* local_state,
EnabledStateProvider* enabled_state_provider,
const StoreClientInfoCallback& store_client_info,
const LoadClientInfoCallback& load_client_info);
// Backs up the current client info via |store_client_info_|.
void BackUpCurrentClientInfo();
// Loads the client info via |load_client_info_| and potentially migrates it
// before returning it if it comes back in its old form.
std::unique_ptr<ClientInfo> LoadClientInfoAndMaybeMigrate();
// Returns the low entropy source for this client. This is a random value
// that is non-identifying amongst browser clients. This method will
// generate the entropy source value if it has not been called before.
int GetLowEntropySource();
// Generates the low entropy source value for this client if it is not
// already set.
void UpdateLowEntropySource();
// Updates |entropy_source_returned_| with |type| iff the current value is
// ENTROPY_SOURCE_NONE and logs the new value in a histogram.
void UpdateEntropySourceReturnedValue(EntropySourceType type);
// Returns the first entropy source that was returned by this service since
// start up, or NONE if neither was returned yet. This is exposed for testing
// only.
EntropySourceType entropy_source_returned() const {
return entropy_source_returned_;
// Reset the client id and low entropy source if the kMetricsResetMetricIDs
// pref is true.
void ResetMetricsIDsIfNecessary();
// Whether an instance of this class exists. Used to enforce that there aren't
// multiple instances of this class at a given time.
static bool instance_exists_;
// Weak pointer to the local state prefs store.
PrefService* const local_state_;
// Weak pointer to an enabled state provider. Used to know whether the user
// has consented to reporting, and if reporting should be done.
EnabledStateProvider* enabled_state_provider_;
// A callback run during client id creation so this MetricsStateManager can
// store a backup of the newly generated ID.
const StoreClientInfoCallback store_client_info_;
// A callback run if this MetricsStateManager can't get the client id from
// its typical location and wants to attempt loading it from this backup.
const LoadClientInfoCallback load_client_info_;
// The identifier that's sent to the server with the log reports.
std::string client_id_;
// The non-identifying low entropy source value.
int low_entropy_source_;
// The last entropy source returned by this service, used for testing.
EntropySourceType entropy_source_returned_;
std::unique_ptr<ClonedInstallDetector> cloned_install_detector_;
} // namespace metrics