components/variations/service/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 COMPONENTS_VARIATIONS_SERVICE_VARIATIONS_SERVICE_H_
   6 #define COMPONENTS_VARIATIONS_SERVICE_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/threading/thread_checker.h"
  17 #include "base/time/time.h"
  18 #include "components/variations/service/variations_service_client.h"
  19 #include "components/variations/variations_request_scheduler.h"
  20 #include "components/variations/variations_seed_simulator.h"
  21 #include "components/variations/variations_seed_store.h"
  22 #include "components/web_resource/resource_request_allowed_notifier.h"
  23 #include "net/url_request/url_fetcher_delegate.h"
  24 #include "url/gurl.h"
  25
  26 class PrefService;
  27 class PrefRegistrySimple;
  28
  29 namespace base {
  30 class Version;
  31 }
  32
  33 namespace metrics {
  34 class MetricsStateManager;
  35 }
  36
  37 namespace user_prefs {
  38 class PrefRegistrySyncable;
  39 }
  40
  41 namespace variations {
  42 class VariationsSeed;
  43 }
  44
  45 namespace variations {
  46
  47 // Used to setup field trials based on stored variations seed data, and fetch
  48 // new seed data from the variations server.
  49 class VariationsService
  50     : public net::URLFetcherDelegate,
  51       public web_resource::ResourceRequestAllowedNotifier::Observer {
  52  public:
  53   class Observer {
  54    public:
  55     // How critical a detected experiment change is. Whether it should be
  56     // handled on a "best-effort" basis or, for a more critical change, if it
  57     // should be given higher priority.
  58     enum Severity {
  59       BEST_EFFORT,
  60       CRITICAL,
  61     };
  62
  63     // Called when the VariationsService detects that there will be significant
  64     // experiment changes on a restart. This notification can then be used to
  65     // update UI (i.e. badging an icon).
  66     virtual void OnExperimentChangesDetected(Severity severity) = 0;
  67
  68    protected:
  69     virtual ~Observer() {}
  70   };
  71
  72   ~VariationsService() override;
  73
  74   // Creates field trials based on Variations Seed loaded from local prefs. If
  75   // there is a problem loading the seed data, all trials specified by the seed
  76   // may not be created.
  77   bool CreateTrialsFromSeed();
  78
  79   // Should be called before startup of the main message loop.
  80   void PerformPreMainMessageLoopStartup();
  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   // Sets the value of the "restrict" URL param to the variations service that
 101   // should be used for variation seed requests. This takes precedence over any
 102   // value coming from policy prefs. This should be called prior to any calls
 103   // to |StartRepeatedVariationsSeedFetch|.
 104   void SetRestrictMode(const std::string& restrict_mode);
 105
 106   // Exposed for testing.
 107   void SetCreateTrialsFromSeedCalledForTesting(bool called);
 108
 109   // Returns the variations server URL, which can vary if a command-line flag is
 110   // set and/or the variations restrict pref is set in |local_prefs|. Declared
 111   // static for test purposes.
 112   GURL GetVariationsServerURL(PrefService* local_prefs,
 113                               const std::string& restrict_mode_override);
 114
 115   // Exposed for testing.
 116   static std::string GetDefaultVariationsServerURLForTesting();
 117
 118   // Register Variations related prefs in Local State.
 119   static void RegisterPrefs(PrefRegistrySimple* registry);
 120
 121   // Register Variations related prefs in the Profile prefs.
 122   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 123
 124   // Factory method for creating a VariationsService. Does not take ownership of
 125   // |state_manager|. Caller should ensure that |state_manager| is valid for the
 126   // lifetime of this class.
 127   static scoped_ptr<VariationsService> Create(
 128       scoped_ptr<VariationsServiceClient> client,
 129       PrefService* local_state,
 130       metrics::MetricsStateManager* state_manager,
 131       const char* disable_network_switch);
 132
 133   // Factory method for creating a VariationsService in a testing context.
 134   static scoped_ptr<VariationsService> CreateForTesting(
 135       scoped_ptr<VariationsServiceClient> client,
 136       PrefService* local_state);
 137
 138   // Set the PrefService responsible for getting policy-related preferences,
 139   // such as the restrict parameter.
 140   void set_policy_pref_service(PrefService* service) {
 141     DCHECK(service);
 142     policy_pref_service_ = service;
 143   }
 144
 145   // Returns the invalid variations seed signature in base64 format, or an empty
 146   // string if the signature was valid, missing, or if signature verification is
 147   // disabled.
 148   std::string GetInvalidVariationsSeedSignature() const;
 149
 150  protected:
 151   // Starts the fetching process once, where |OnURLFetchComplete| is called with
 152   // the response.
 153   virtual void DoActualFetch();
 154
 155   // Stores the seed to prefs. Set as virtual and protected so that it can be
 156   // overridden by tests.
 157   virtual bool StoreSeed(const std::string& seed_data,
 158                          const std::string& seed_signature,
 159                          const std::string& country_code,
 160                          const base::Time& date_fetched,
 161                          bool is_delta_compressed);
 162
 163   // Creates the VariationsService with the given |local_state| prefs service
 164   // and |state_manager|. Does not take ownership of |state_manager|. Caller
 165   // should ensure that |state_manager| is valid for the lifetime of this class.
 166   // Use the |Create| factory method to create a VariationsService.
 167   VariationsService(
 168       scoped_ptr<VariationsServiceClient> client,
 169       scoped_ptr<web_resource::ResourceRequestAllowedNotifier> notifier,
 170       PrefService* local_state,
 171       metrics::MetricsStateManager* state_manager);
 172
 173  private:
 174   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, Observer);
 175   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, SeedStoredWhenOKStatus);
 176   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, SeedNotStoredWhenNonOKStatus);
 177   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, SeedDateUpdatedOn304Status);
 178   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest,
 179                            LoadPermanentConsistencyCountry);
 180   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CountryHeader);
 181   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, GetVariationsServerURL);
 182
 183   // Set of different possible values to report for the
 184   // Variations.LoadPermanentConsistencyCountryResult histogram. This enum must
 185   // be kept consistent with its counterpart in histograms.xml.
 186   enum LoadPermanentConsistencyCountryResult {
 187     LOAD_COUNTRY_NO_PREF_NO_SEED = 0,
 188     LOAD_COUNTRY_NO_PREF_HAS_SEED,
 189     LOAD_COUNTRY_INVALID_PREF_NO_SEED,
 190     LOAD_COUNTRY_INVALID_PREF_HAS_SEED,
 191     LOAD_COUNTRY_HAS_PREF_NO_SEED_VERSION_EQ,
 192     LOAD_COUNTRY_HAS_PREF_NO_SEED_VERSION_NEQ,
 193     LOAD_COUNTRY_HAS_BOTH_VERSION_EQ_COUNTRY_EQ,
 194     LOAD_COUNTRY_HAS_BOTH_VERSION_EQ_COUNTRY_NEQ,
 195     LOAD_COUNTRY_HAS_BOTH_VERSION_NEQ_COUNTRY_EQ,
 196     LOAD_COUNTRY_HAS_BOTH_VERSION_NEQ_COUNTRY_NEQ,
 197     LOAD_COUNTRY_MAX,
 198   };
 199
 200   // Checks if prerequisites for fetching the Variations seed are met, and if
 201   // so, performs the actual fetch using |DoActualFetch|.
 202   void FetchVariationsSeed();
 203
 204   // Notify any observers of this service based on the simulation |result|.
 205   void NotifyObservers(
 206       const variations::VariationsSeedSimulator::Result& result);
 207
 208   // net::URLFetcherDelegate implementation:
 209   void OnURLFetchComplete(const net::URLFetcher* source) override;
 210
 211   // ResourceRequestAllowedNotifier::Observer implementation:
 212   void OnResourceRequestsAllowed() override;
 213
 214   // Performs a variations seed simulation with the given |seed| and |version|
 215   // and logs the simulation results as histograms.
 216   void PerformSimulationWithVersion(scoped_ptr<variations::VariationsSeed> seed,
 217                                     const base::Version& version);
 218
 219   // Record the time of the most recent successful fetch.
 220   void RecordLastFetchTime();
 221
 222   // Loads the country code to use for filtering permanent consistency studies,
 223   // updating the stored country code if the stored value was for a different
 224   // Chrome version. The country used for permanent consistency studies is kept
 225   // consistent between Chrome upgrades in order to avoid annoying the user due
 226   // to experiment churn while traveling.
 227   std::string LoadPermanentConsistencyCountry(
 228       const base::Version& version,
 229       const std::string& latest_country);
 230
 231   scoped_ptr<VariationsServiceClient> client_;
 232
 233   // The pref service used to store persist the variations seed.
 234   PrefService* local_state_;
 235
 236   // Used for instantiating entropy providers for variations seed simulation.
 237   // Weak pointer.
 238   metrics::MetricsStateManager* state_manager_;
 239
 240   // Used to obtain policy-related preferences. Depending on the platform, will
 241   // either be Local State or Profile prefs.
 242   PrefService* policy_pref_service_;
 243
 244   VariationsSeedStore seed_store_;
 245
 246   // Contains the scheduler instance that handles timing for requests to the
 247   // server. Initially NULL and instantiated when the initial fetch is
 248   // requested.
 249   scoped_ptr<VariationsRequestScheduler> request_scheduler_;
 250
 251   // Contains the current seed request. Will only have a value while a request
 252   // is pending, and will be reset by |OnURLFetchComplete|.
 253   scoped_ptr<net::URLFetcher> pending_seed_request_;
 254
 255   // The value of the "restrict" URL param to the variations server that has
 256   // been specified via |SetRestrictMode|. If empty, the URL param will be set
 257   // based on policy prefs.
 258   std::string restrict_mode_;
 259
 260   // The URL to use for querying the variations server.
 261   GURL variations_server_url_;
 262
 263   // Tracks whether |CreateTrialsFromSeed| has been called, to ensure that
 264   // it gets called prior to |StartRepeatedVariationsSeedFetch|.
 265   bool create_trials_from_seed_called_;
 266
 267   // Tracks whether the initial request to the variations server had completed.
 268   bool initial_request_completed_;
 269
 270   // Indicates that the next request to the variations service shouldn't specify
 271   // that it supports delta compression. Set to true when a delta compressed
 272   // response encountered an error.
 273   bool disable_deltas_for_next_request_;
 274
 275   // Helper class used to tell this service if it's allowed to make network
 276   // resource requests.
 277   scoped_ptr<web_resource::ResourceRequestAllowedNotifier>
 278       resource_request_allowed_notifier_;
 279
 280   // The start time of the last seed request. This is used to measure the
 281   // latency of seed requests. Initially zero.
 282   base::TimeTicks last_request_started_time_;
 283
 284   // The number of requests to the variations server that have been performed.
 285   int request_count_;
 286
 287   // List of observers of the VariationsService.
 288   base::ObserverList<Observer> observer_list_;
 289
 290   base::ThreadChecker thread_checker_;
 291
 292   base::WeakPtrFactory<VariationsService> weak_ptr_factory_;
 293
 294   DISALLOW_COPY_AND_ASSIGN(VariationsService);
 295 };
 296
 297 }  // namespace variations
 298
 299 #endif  // COMPONENTS_VARIATIONS_SERVICE_VARIATIONS_SERVICE_H_