components/proximity_auth/cryptauth/sync_scheduler.h

   1 // Copyright 2015 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_PROXIMITY_AUTH_CRYPTAUTH_SYNC_SCHEDULER_H
   6 #define COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_SYNC_SCHEDULER_H
   7
   8 #include "base/memory/weak_ptr.h"
   9 #include "base/time/time.h"
  10
  11 namespace proximity_auth {
  12
  13 // Interface for scheduling the next CryptAuth sync (e.g. enrollment or device
  14 // sync). The scheduler has two different strategies affecting when to perform
  15 // the next operation:
  16 //     PERIODIC_REFRESH: The last sync was made successfully, so we can wait a
  17 //         relatively long time before making another sync.
  18 //     AGGRESSIVE_RECOVERY: The last sync failed, so we try more aggressively to
  19 //         make enrollment attempts with subsequent backoff for repeated
  20 //         failures.
  21 // A random jitter is applied to each sync period to smooth qps to the server.
  22 class SyncScheduler {
  23  public:
  24   // The sync strategies mentioned in the class comments.
  25   enum class Strategy { PERIODIC_REFRESH, AGGRESSIVE_RECOVERY };
  26
  27   // The states that the scheduler can be in.
  28   enum class SyncState { NOT_STARTED, WAITING_FOR_REFRESH, SYNC_IN_PROGRESS };
  29
  30   // An instance is passed to the delegate when the scheduler fires for each
  31   // sync attempt. The delegate should call |Complete()| when the sync succeeds
  32   // or fails to resume the scheduler.
  33   class SyncRequest {
  34    public:
  35     explicit SyncRequest(base::WeakPtr<SyncScheduler> sync_scheduler);
  36     ~SyncRequest();
  37
  38     void OnDidComplete(bool success);
  39
  40    protected:
  41     // The parent scheduler that dispatched this request.
  42     base::WeakPtr<SyncScheduler> sync_scheduler_;
  43
  44     // True if |OnDidComplete()| has been called.
  45     bool completed_;
  46
  47     DISALLOW_COPY_AND_ASSIGN(SyncRequest);
  48   };
  49
  50   // Handles the actual sync operation.
  51   class Delegate {
  52    public:
  53     virtual ~Delegate() {}
  54
  55     // Called when the scheduler fires and requests a sync attempt. The delegate
  56     // should call sync_request->Complete() when the request finishes.
  57     virtual void OnSyncRequested(scoped_ptr<SyncRequest> sync_request) = 0;
  58   };
  59
  60   virtual ~SyncScheduler() {}
  61
  62   // Starts the scheduler with an aggressive recovery strategy if
  63   // |strategy| is true; otherwise, it will be started with
  64   // periodic refresh.
  65   //
  66   // |elapsed_time_since_last_sync| is the time since the last successful sync,
  67   // so we can determine the duration of the first sync period. For example, the
  68   // scheduler will immediately issue a sync request if the elapsed time is
  69   // greater than the refresh period.
  70   virtual void Start(const base::TimeDelta& elapsed_time_since_last_sync,
  71                      Strategy strategy) = 0;
  72
  73   // Cancels the current scheduled sync, and forces a sync immediately. Note
  74   // that if this sync fails, the scheduler will adopt the AGGRESSIVE_RECOVERY
  75   // strategy.
  76   virtual void ForceSync() = 0;
  77
  78   // Returns the time until the next scheduled sync operation. If no sync is
  79   // scheduled, a TimeDelta of zero will be returned.
  80   virtual base::TimeDelta GetTimeToNextSync() const = 0;
  81
  82   // Returns the current sync strategy.
  83   virtual Strategy GetStrategy() const = 0;
  84
  85   // Returns the current state of the scheduler.
  86   virtual SyncState GetSyncState() const = 0;
  87
  88  protected:
  89   // Called by SyncRequest instances when the sync completes.
  90   virtual void OnSyncCompleted(bool success) = 0;
  91 };
  92
  93 }  // namespace proximity_auth
  94
  95 #endif  // COMPONENTS_PROXIMITY_CRYPTAUTH_SYNC_SCHEDULER_H