entity_tracker.h revision 116680a4aac90f2aa7413d9095a592090648e557 
1// Copyright 2014 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_ENGINE_ENTITY_TRACKER_H_
6#define SYNC_ENGINE_ENTITY_TRACKER_H_
7
8#include <string>
9
10#include "base/basictypes.h"
11#include "base/time/time.h"
12#include "sync/base/sync_export.h"
13#include "sync/protocol/sync.pb.h"
14
15namespace syncer {
16
17// Manages the pending commit and update state for an entity on the sync
18// thread.
19//
20// It should be considered a helper class internal to the
21// ModelTypeSyncWorker.
22//
23// Maintains the state associated with a particular sync entity which is
24// necessary for decision-making on the sync thread.  It can track pending
25// commit state, received update state, and can detect conflicts.
26//
27// This object may or may not contain state associated with a pending commit.
28// If no commit is pending, the |is_commit_pending_| flag will be set to false
29// and many of this object's fields will be cleared.
30class SYNC_EXPORT EntityTracker {
31 public:
32  ~EntityTracker();
33
34  // Initialize a new entity based on an update response.
35  static EntityTracker* FromServerUpdate(const std::string& id_string,
36                                         const std::string& client_tag_hash,
37                                         int64 version);
38
39  // Initialize a new entity based on a commit request.
40  static EntityTracker* FromCommitRequest(
41      const std::string& id_string,
42      const std::string& client_tag_hash,
43      int64 sequence_number,
44      int64 base_version,
45      base::Time ctime,
46      base::Time mtime,
47      const std::string& non_unique_name,
48      bool deleted,
49      const sync_pb::EntitySpecifics& specifics);
50
51  // Returns true if this entity should be commited to the server.
52  bool IsCommitPending() const;
53
54  // Populates a sync_pb::SyncEntity for a commit.  Also sets the
55  // |sequence_number|, so we can track it throughout the commit process.
56  void PrepareCommitProto(sync_pb::SyncEntity* commit_entity,
57                          int64* sequence_number) const;
58
59  // Updates this entity with data from the latest version that the
60  // model asked us to commit.  May clobber state related to the
61  // model's previous commit attempt(s).
62  void RequestCommit(const std::string& id,
63                     const std::string& client_tag_hash,
64                     int64 sequence_number,
65                     int64 base_version,
66                     base::Time ctime,
67                     base::Time mtime,
68                     const std::string& non_unique_name,
69                     bool deleted,
70                     const sync_pb::EntitySpecifics& specifics);
71
72  // Handles the receipt of a commit response.
73  //
74  // Since commits happen entirely on the sync thread, we can safely assume
75  // that our item's state at the end of the commit is the same as it was at
76  // the start.
77  void ReceiveCommitResponse(const std::string& response_id,
78                             int64 response_version,
79                             int64 sequence_number);
80
81  // Handles receipt of an update from the server.
82  void ReceiveUpdate(int64 version);
83
84 private:
85  // Initializes received update state.  Does not initialize state related to
86  // pending commits and sets |is_commit_pending_| to false.
87  EntityTracker(const std::string& id,
88                const std::string& client_tag_hash,
89                int64 highest_commit_response_version,
90                int64 highest_gu_response_version);
91
92  // Initializes all fields.  Sets |is_commit_pending_| to true.
93  EntityTracker(const std::string& id,
94                const std::string& client_tag_hash,
95                int64 highest_commit_response_version,
96                int64 highest_gu_response_version,
97                bool is_commit_pending,
98                int64 sequence_number,
99                int64 base_version,
100                base::Time ctime,
101                base::Time mtime,
102                const std::string& non_unique_name,
103                bool deleted,
104                const sync_pb::EntitySpecifics& specifics);
105
106  // Checks if the current state indicates a conflict.
107  //
108  // This can be true only while a call to this object is in progress.
109  // Conflicts are always cleared before the method call ends.
110  bool IsInConflict() const;
111
112  // Checks if the server knows about this item.
113  bool IsServerKnown() const;
114
115  // Clears flag and optionally clears state associated with a pending commit.
116  void ClearPendingCommit();
117
118  // The ID for this entry.  May be empty if the entry has never been committed.
119  std::string id_;
120
121  // The hashed client tag for this entry.
122  std::string client_tag_hash_;
123
124  // The highest version seen in a commit response for this entry.
125  int64 highest_commit_response_version_;
126
127  // The highest version seen in a GU response for this entry.
128  int64 highest_gu_response_version_;
129
130  // Flag that indicates whether or not we're waiting for a chance to commit
131  // this item.
132  bool is_commit_pending_;
133
134  // Used to track in-flight commit requests on the model thread.  All we need
135  // to do here is return it back to the model thread when the pending commit
136  // is completed and confirmed.  Not valid if no commit is pending.
137  int64 sequence_number_;
138
139  // The following fields are valid only when a commit is pending.
140  // This is where we store the data that is to be sent up to the server
141  // at the next possible opportunity.
142  int64 base_version_;
143  base::Time ctime_;
144  base::Time mtime_;
145  std::string non_unique_name_;
146  bool deleted_;
147  sync_pb::EntitySpecifics specifics_;
148
149  DISALLOW_COPY_AND_ASSIGN(EntityTracker);
150};
151
152}  // namespace syncer
153
154#endif  // SYNC_ENGINE_ENTITY_TRACKER_H_
155