chrome/browser/metrics/variations/variations_service.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_
   6 #define CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_
   7
   8 #include <string>
   9
  10 #include "base/compiler_specific.h"
  11 #include "base/gtest_prod_util.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/memory/weak_ptr.h"
  14 #include "base/metrics/field_trial.h"
  15 #include "base/observer_list.h"
  16 #include "base/time/time.h"
  17 #include "chrome/browser/metrics/variations/variations_request_scheduler.h"
  18 #include "chrome/browser/metrics/variations/variations_seed_store.h"
  19 #include "chrome/common/chrome_version_info.h"
  20 #include "components/variations/variations_seed_simulator.h"
  21 #include "components/web_resource/resource_request_allowed_notifier.h"
  22 #include "net/url_request/url_fetcher_delegate.h"
  23 #include "url/gurl.h"
  24
  25 #if defined(OS_WIN)
  26 #include "chrome/browser/metrics/variations/variations_registry_syncer_win.h"
  27 #endif
  28
  29 class PrefService;
  30 class PrefRegistrySimple;
  31
  32 namespace base {
  33 class Version;
  34 }
  35
  36 namespace metrics {
  37 class MetricsStateManager;
  38 }
  39
  40 namespace user_prefs {
  41 class PrefRegistrySyncable;
  42 }
  43
  44 namespace variations {
  45 class VariationsSeed;
  46 }
  47
  48 namespace chrome_variations {
  49
  50 // Used to setup field trials based on stored variations seed data, and fetch
  51 // new seed data from the variations server.
  52 class VariationsService
  53     : public net::URLFetcherDelegate,
  54       public web_resource::ResourceRequestAllowedNotifier::Observer {
  55  public:
  56   class Observer {
  57    public:
  58     // How critical a detected experiment change is. Whether it should be
  59     // handled on a "best-effort" basis or, for a more critical change, if it
  60     // should be given higher priority.
  61     enum Severity {
  62       BEST_EFFORT,
  63       CRITICAL,
  64     };
  65
  66     // Called when the VariationsService detects that there will be significant
  67     // experiment changes on a restart. This notification can then be used to
  68     // update UI (i.e. badging an icon).
  69     virtual void OnExperimentChangesDetected(Severity severity) = 0;
  70
  71    protected:
  72     virtual ~Observer() {}
  73   };
  74
  75   ~VariationsService() override;
  76
  77   // Creates field trials based on Variations Seed loaded from local prefs. If
  78   // there is a problem loading the seed data, all trials specified by the seed
  79   // may not be created.
  80   bool CreateTrialsFromSeed();
  81
  82   // Calls FetchVariationsSeed once and repeats this periodically. See
  83   // implementation for details on the period. Must be called after
  84   // |CreateTrialsFromSeed|.
  85   void StartRepeatedVariationsSeedFetch();
  86
  87   // Adds an observer to listen for detected experiment changes.
  88   void AddObserver(Observer* observer);
  89
  90   // Removes a previously-added observer.
  91   void RemoveObserver(Observer* observer);
  92
  93   // Called when the application enters foreground. This may trigger a
  94   // FetchVariationsSeed call.
  95   // TODO(rkaplow): Handle this and the similar event in metrics_service by
  96   // observing an 'OnAppEnterForeground' event instead of requiring the frontend
  97   // code to notify each service individually.
  98   void OnAppEnterForeground();
  99
 100 #if defined(OS_WIN)
 101   // Starts syncing Google Update Variation IDs with the registry.
 102   void StartGoogleUpdateRegistrySync();
 103 #endif
 104
 105   // Sets the value of the "restrict" URL param to the variations service that
 106   // should be used for variation seed requests. This takes precedence over any
 107   // value coming from policy prefs. This should be called prior to any calls
 108   // to |StartRepeatedVariationsSeedFetch|.
 109   void SetRestrictMode(const std::string& restrict_mode);
 110
 111   // Exposed for testing.
 112   void SetCreateTrialsFromSeedCalledForTesting(bool called);
 113
 114   // Returns the variations server URL, which can vary if a command-line flag is
 115   // set and/or the variations restrict pref is set in |local_prefs|. Declared
 116   // static for test purposes.
 117   static GURL GetVariationsServerURL(PrefService* local_prefs,
 118                                      const std::string& restrict_mode_override);
 119
 120   // Exposed for testing.
 121   static std::string GetDefaultVariationsServerURLForTesting();
 122
 123   // Register Variations related prefs in Local State.
 124   static void RegisterPrefs(PrefRegistrySimple* registry);
 125
 126   // Register Variations related prefs in the Profile prefs.
 127   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 128
 129   // Factory method for creating a VariationsService. Does not take ownership of
 130   // |state_manager|. Caller should ensure that |state_manager| is valid for the
 131   // lifetime of this class.
 132   static scoped_ptr<VariationsService> Create(
 133       PrefService* local_state,
 134       metrics::MetricsStateManager* state_manager);
 135
 136   // Set the PrefService responsible for getting policy-related preferences,
 137   // such as the restrict parameter.
 138   void set_policy_pref_service(PrefService* service) {
 139     DCHECK(service);
 140     policy_pref_service_ = service;
 141   }
 142
 143   // Returns the invalid variations seed signature in base64 format, or an empty
 144   // string if the signature was valid, missing, or if signature verification is
 145   // disabled.
 146   std::string GetInvalidVariationsSeedSignature() const;
 147
 148  protected:
 149   // Starts the fetching process once, where |OnURLFetchComplete| is called with
 150   // the response.
 151   virtual void DoActualFetch();
 152
 153   // Stores the seed to prefs. Set as virtual and protected so that it can be
 154   // overridden by tests.
 155   virtual void StoreSeed(const std::string& seed_data,
 156                          const std::string& seed_signature,
 157                          const base::Time& date_fetched);
 158
 159   // Creates the VariationsService with the given |local_state| prefs service
 160   // and |state_manager|. This instance will take ownership of |notifier|.
 161   // Does not take ownership of |state_manager|. Caller should ensure that
 162   // |state_manager| is valid for the lifetime of this class. Use the |Create|
 163   // factory method to create a VariationsService.
 164   VariationsService(web_resource::ResourceRequestAllowedNotifier* notifier,
 165                     PrefService* local_state,
 166                     metrics::MetricsStateManager* state_manager);
 167
 168  private:
 169   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, Observer);
 170   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, SeedStoredWhenOKStatus);
 171   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, SeedNotStoredWhenNonOKStatus);
 172   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, SeedDateUpdatedOn304Status);
 173
 174   // Checks if prerequisites for fetching the Variations seed are met, and if
 175   // so, performs the actual fetch using |DoActualFetch|.
 176   void FetchVariationsSeed();
 177
 178   // Notify any observers of this service based on the simulation |result|.
 179   void NotifyObservers(
 180       const variations::VariationsSeedSimulator::Result& result);
 181
 182   // net::URLFetcherDelegate implementation:
 183   void OnURLFetchComplete(const net::URLFetcher* source) override;
 184
 185   // ResourceRequestAllowedNotifier::Observer implementation:
 186   void OnResourceRequestsAllowed() override;
 187
 188   // Performs a variations seed simulation with the given |seed| and |version|
 189   // and logs the simulation results as histograms.
 190   void PerformSimulationWithVersion(scoped_ptr<variations::VariationsSeed> seed,
 191                                     const base::Version& version);
 192
 193   // Record the time of the most recent successful fetch.
 194   void RecordLastFetchTime();
 195
 196   // The pref service used to store persist the variations seed.
 197   PrefService* local_state_;
 198
 199   // Used for instantiating entropy providers for variations seed simulation.
 200   // Weak pointer.
 201   metrics::MetricsStateManager* state_manager_;
 202
 203   // Used to obtain policy-related preferences. Depending on the platform, will
 204   // either be Local State or Profile prefs.
 205   PrefService* policy_pref_service_;
 206
 207   VariationsSeedStore seed_store_;
 208
 209   // Contains the scheduler instance that handles timing for requests to the
 210   // server. Initially NULL and instantiated when the initial fetch is
 211   // requested.
 212   scoped_ptr<VariationsRequestScheduler> request_scheduler_;
 213
 214   // Contains the current seed request. Will only have a value while a request
 215   // is pending, and will be reset by |OnURLFetchComplete|.
 216   scoped_ptr<net::URLFetcher> pending_seed_request_;
 217
 218   // The value of the "restrict" URL param to the variations server that has
 219   // been specified via |SetRestrictMode|. If empty, the URL param will be set
 220   // based on policy prefs.
 221   std::string restrict_mode_;
 222
 223   // The URL to use for querying the variations server.
 224   GURL variations_server_url_;
 225
 226   // Tracks whether |CreateTrialsFromSeed| has been called, to ensure that
 227   // it gets called prior to |StartRepeatedVariationsSeedFetch|.
 228   bool create_trials_from_seed_called_;
 229
 230   // Tracks whether the initial request to the variations server had completed.
 231   bool initial_request_completed_;
 232
 233   // Helper class used to tell this service if it's allowed to make network
 234   // resource requests.
 235   scoped_ptr<web_resource::ResourceRequestAllowedNotifier>
 236       resource_request_allowed_notifier_;
 237
 238   // The start time of the last seed request. This is used to measure the
 239   // latency of seed requests. Initially zero.
 240   base::TimeTicks last_request_started_time_;
 241
 242   // List of observers of the VariationsService.
 243   ObserverList<Observer> observer_list_;
 244
 245 #if defined(OS_WIN)
 246   // Helper that handles synchronizing Variations with the Registry.
 247   VariationsRegistrySyncer registry_syncer_;
 248 #endif
 249
 250   base::WeakPtrFactory<VariationsService> weak_ptr_factory_;
 251
 252   DISALLOW_COPY_AND_ASSIGN(VariationsService);
 253 };
 254
 255 }  // namespace chrome_variations
 256
 257 #endif  // CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_