[Sync] Refactoring polling to be reliable.

sync/engine/sync_scheduler_impl.h

 // Copyright 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.
 
 #ifndef SYNC_ENGINE_SYNC_SCHEDULER_IMPL_H_
 #define SYNC_ENGINE_SYNC_SCHEDULER_IMPL_H_
 
 #include <map>
 #include <string>
 
@@ skipping 33 matching lines @@
   // |name| is a display string to identify the syncer thread.  Takes
   // |ownership of |syncer| and |delay_provider|.
   SyncSchedulerImpl(const std::string& name,
                     BackoffDelayProvider* delay_provider,
                     sessions::SyncSessionContext* context,
                     Syncer* syncer);
 
   // Calls Stop().
   ~SyncSchedulerImpl() override;
 
-  void Start(Mode mode) override;
+  void Start(Mode mode, base::Time last_poll_time) override;
   void ScheduleConfiguration(const ConfigurationParams& params) override;
   void Stop() override;
   void ScheduleLocalNudge(
       ModelTypeSet types,
       const tracked_objects::Location& nudge_location) override;
   void ScheduleLocalRefreshRequest(
       ModelTypeSet types,
       const tracked_objects::Location& nudge_location) override;
   void ScheduleInvalidationNudge(
       syncer::ModelType type,
@@ skipping 79 matching lines @@
   static const char* GetModeString(Mode mode);
 
   void SetDefaultNudgeDelay(base::TimeDelta delay_ms);
 
   // Invoke the syncer to perform a nudge job.
   void DoNudgeSyncSessionJob(JobPriority priority);
 
   // Invoke the syncer to perform a configuration job.
   void DoConfigurationSyncSessionJob(JobPriority priority);
 
-  // Helper function for Do{Nudge,Configuration}SyncSessionJob.
+  // Helper function for Do{Nudge,Configuration,Poll}SyncSessionJob.
+  void HandleSuccess();
+
+  // Helper function for Do{Nudge,Configuration,Poll}SyncSessionJob.
   void HandleFailure(
       const sessions::ModelNeutralState& model_neutral_state);
 
   // Invoke the Syncer to perform a poll job.
   void DoPollSyncSessionJob();
 
   // Helper function to calculate poll interval.
   base::TimeDelta GetPollInterval();
 
   // Adjusts the poll timer to account for new poll interval, and possibly
@@ skipping 74 matching lines @@
   const std::string name_;
 
   // Set in Start(), unset in Stop().
   bool started_;
 
   // Modifiable versions of kDefaultLongPollIntervalSeconds which can be
   // updated by the server.
   base::TimeDelta syncer_short_poll_interval_seconds_;
   base::TimeDelta syncer_long_poll_interval_seconds_;
 
-  // Periodic timer for polling.  See AdjustPolling.
-  base::RepeatingTimer<SyncSchedulerImpl> poll_timer_;
+  // Timer for polling. Restarted on each successful poll, and when entering
+  // normal sync mode or exiting an error state. Not active in configuration
+  // mode.
+  base::OneShotTimer<SyncSchedulerImpl> poll_timer_;
 
   // The mode of operation.
   Mode mode_;
 
   // Current wait state.  Null if we're not in backoff and not throttled.
   scoped_ptr<WaitInterval> wait_interval_;
 
   scoped_ptr<BackoffDelayProvider> delay_provider_;
 
   // The event that will wake us up.
@@ skipping 23 matching lines @@
   typedef std::map<ModelType, base::TimeTicks> ModelTypeTimeMap;
   ModelTypeTimeMap last_local_nudges_by_model_type_;
 
   // Used as an "anti-reentrancy defensive assertion".
   // While true, it is illegal for any new scheduling activity to take place.
   // Ensures that higher layers don't break this law in response to events that
   // take place during a sync cycle. We call this out because such violations
   // could result in tight sync loops hitting sync servers.
   bool no_scheduling_allowed_;
 
-  // crbug/251307. This is a workaround for M29. crbug/259913 tracks proper fix
-  // for M30.
-  // The issue is that poll job runs after few hours of inactivity and therefore
-  // will always fail with auth error because of expired access token. Once
-  // fresh access token is requested poll job is not retried.
-  // The change is to remember that poll timer just fired and retry poll job
-  // after credentials are updated.
-  bool do_poll_after_credentials_updated_;
-
   // TryJob might get called for multiple reasons. It should only call
   // DoPollSyncSessionJob after some time since the last attempt.
   // last_poll_reset_ keeps track of when was last attempt.
   base::TimeTicks last_poll_reset_;
 
   // next_sync_session_job_priority_ defines which priority will be used next
   // time TrySyncSessionJobImpl is called. CANARY_PRIORITY allows syncer to run
   // even if scheduler is in exponential backoff. This is needed for events that
   // have chance of resolving previous error (e.g. network connection change
   // after NETWORK_UNAVAILABLE error).
   // It is reset back to NORMAL_PRIORITY on every call to TrySyncSessionJobImpl.
   JobPriority next_sync_session_job_priority_;
 
   // One-shot timer for scheduling GU retry according to delay set by server.
   base::OneShotTimer<SyncSchedulerImpl> retry_timer_;
 
   base::WeakPtrFactory<SyncSchedulerImpl> weak_ptr_factory_;
 
   // A second factory specially for weak_handle_this_, to allow the handle
   // to be const and alleviate threading concerns.
   base::WeakPtrFactory<SyncSchedulerImpl> weak_ptr_factory_for_weak_handle_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncSchedulerImpl);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_SYNC_SCHEDULER_IMPL_H_