sync/notifier/dropped_invalidation_tracker.h

   1 // Copyright 2013 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 SYNC_NOTIFIER_DROPPED_INVALIDATION_TRACKER_H_
   6 #define SYNC_NOTIFIER_DROPPED_INVALIDATION_TRACKER_H_
   7
   8 #include "google/cacheinvalidation/include/types.h"
   9 #include "sync/base/sync_export.h"
  10 #include "sync/internal_api/public/base/ack_handle.h"
  11 #include "sync/internal_api/public/util/weak_handle.h"
  12 #include "sync/notifier/ack_handler.h"
  13
  14 namespace syncer {
  15
  16 class Invalidation;
  17
  18 // Helps InvalidationHandlers keep track of dropped invalidations for a given
  19 // ObjectId.
  20 //
  21 // The intent of this class is to hide some of the implementation details around
  22 // how the invalidations system manages dropping and drop recovery.  Any
  23 // invalidation handler that intends to buffer and occasionally drop
  24 // invalidations should keep one instance of it per registered ObjectId.
  25 //
  26 // When an invalidation handler wishes to drop an invalidation, it must provide
  27 // an instance of this class to that Invalidation's Drop() method.  In order to
  28 // indicate recovery from a drop, the handler can call this class'
  29 // RecordRecoveryFromDropEvent().
  30 //
  31 // Copy and assign are allowed for this class so we can use it in STL
  32 // containers.
  33 class SYNC_EXPORT DroppedInvalidationTracker {
  34  public:
  35   explicit DroppedInvalidationTracker(const invalidation::ObjectId& id);
  36   ~DroppedInvalidationTracker();
  37
  38   const invalidation::ObjectId& object_id() const;
  39
  40   // Called by Invalidation::Drop() to keep track of a drop event.
  41   //
  42   // Takes ownership of the internals belonging to a soon to be discarded
  43   // dropped invalidation.  See also the comment for this class'
  44   // |drop_ack_handler_| member.
  45   void RecordDropEvent(WeakHandle<AckHandler> handler, AckHandle handle);
  46
  47   // Returns true if we're still recovering from a drop event.
  48   bool IsRecoveringFromDropEvent() const;
  49
  50   // Called by the InvalidationHandler when it recovers from the drop event.
  51   void RecordRecoveryFromDropEvent();
  52
  53  private:
  54   invalidation::ObjectId id_;
  55   AckHandle drop_ack_handle_;
  56
  57   // This flag is set to true when we have dropped an invalidation and have not
  58   // yet recovered from this drop event.  Note that this may not always coincide
  59   // with drop_ack_handler_ being initialized because a null AckHandler could be
  60   // passed in to RecordDropEvent().
  61   bool recovering_from_drop_;
  62
  63   // A WeakHandle to the enitity responsible for persisting invalidation
  64   // acknowledgement state on disk.  We can get away with using a WeakHandle
  65   // because we don't care if our drop recovery message doesn't gets delivered
  66   // in some shutdown cases.  If that happens, we'll have to process the
  67   // invalidation state again on the next restart.  It would be a waste of time
  68   // and resources, but otherwise not particularly harmful.
  69   WeakHandle<AckHandler> drop_ack_handler_;
  70 };
  71
  72 }  // namespace syncer
  73
  74 #endif  // SYNC_NOTIFIER_DROPPED_INVALIDATION_TRACKER_H_