Implement new invalidations ack tracking system

sync/notifier/ack_tracker.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_NOTIFIER_ACK_TRACKER_H_
-#define SYNC_NOTIFIER_ACK_TRACKER_H_
-
-#include <map>
-
-#include "base/basictypes.h"
-#include "base/callback_forward.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/threading/thread_checker.h"
-#include "base/time/time.h"
-#include "base/timer/timer.h"
-#include "net/base/backoff_entry.h"
-#include "sync/base/sync_export.h"
-#include "sync/notifier/invalidation_util.h"
-
-namespace base {
-class TickClock;
-}  // namespace base
-
-namespace syncer {
-
-// A simple class that tracks sets of object IDs that have not yet been
-// acknowledged. Internally, it manages timeouts for the tracked object IDs and
-// periodically triggers a callback for each timeout period. The timeout is a
-// simple exponentially increasing time that starts at 60 seconds and is capped
-// at 600 seconds.
-class SYNC_EXPORT_PRIVATE AckTracker {
- public:
-  class SYNC_EXPORT_PRIVATE Delegate {
-   public:
-    virtual ~Delegate();
-
-    // |ids| contains all object IDs that have timed out in this time interval.
-    virtual void OnTimeout(const ObjectIdSet& ids) = 0;
-  };
-
-  typedef base::Callback<scoped_ptr<net::BackoffEntry>(
-      const net::BackoffEntry::Policy* const)> CreateBackoffEntryCallback;
-
-  AckTracker(base::TickClock* tick_clock, Delegate* delegate);
-  ~AckTracker();
-
-  // Equivalent to calling Ack() on all currently registered object IDs.
-  void Clear();
-
-  // Starts tracking timeouts for |ids|. Timeouts will be triggered for each
-  // object ID until it is acknowledged. Note that no de-duplication is
-  // performed; calling Track() twice on the same set of ids will result in two
-  // different timeouts being triggered for those ids.
-  void Track(const ObjectIdSet& ids);
-  // Marks a set of |ids| as acknowledged.
-  void Ack(const ObjectIdSet& ids);
-
-  // Testing methods.
-  void SetCreateBackoffEntryCallbackForTest(
-      const CreateBackoffEntryCallback& create_backoff_entry_callback);
-  // Returns true iff there are no timeouts scheduled to occur before |now|.
-  // Used in testing to make sure we don't have timeouts set to expire before
-  // when they should.
-  bool TriggerTimeoutAtForTest(base::TimeTicks now);
-  bool IsQueueEmptyForTest() const;
-  const base::Timer& GetTimerForTest() const;
-
- private:
-  struct Entry {
-    Entry(scoped_ptr<net::BackoffEntry> backoff, const ObjectIdSet& ids);
-    ~Entry();
-
-    scoped_ptr<net::BackoffEntry> backoff;
-    ObjectIdSet ids;
-
-   private:
-    DISALLOW_COPY_AND_ASSIGN(Entry);
-  };
-
-  void NudgeTimer();
-  void OnTimeout();
-  void OnTimeoutAt(base::TimeTicks now);
-
-  static scoped_ptr<net::BackoffEntry> DefaultCreateBackoffEntryStrategy(
-      const net::BackoffEntry::Policy* const policy);
-
-  // Used for testing purposes.
-  CreateBackoffEntryCallback create_backoff_entry_callback_;
-
-  base::TickClock* const tick_clock_;
-
-  Delegate* const delegate_;
-
-  base::OneShotTimer<AckTracker> timer_;
-  // The time that the timer should fire at. We use this to determine if we need
-  // to start or update |timer_| in NudgeTimer(). We can't simply use
-  // timer_.desired_run_time() for this purpose because it always uses
-  // base::TimeTicks::Now() as a reference point when Timer::Start() is called,
-  // while NudgeTimer() needs a fixed reference point to avoid unnecessarily
-  // updating the timer.
-  base::TimeTicks desired_run_time_;
-  std::multimap<base::TimeTicks, Entry*> queue_;
-
-  base::ThreadChecker thread_checker_;
-
-  DISALLOW_COPY_AND_ASSIGN(AckTracker);
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_NOTIFIER_ACK_TRACKER_H_