1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
|
/**
* Copyright (C) 2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <boost/optional.hpp>
#include <wiredtiger.h>
#include "mongo/base/disallow_copying.h"
#include "mongo/bson/timestamp.h"
#include "mongo/db/storage/snapshot_manager.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
class WiredTigerOplogManager;
class WiredTigerSnapshotManager final : public SnapshotManager {
MONGO_DISALLOW_COPYING(WiredTigerSnapshotManager);
public:
WiredTigerSnapshotManager() = default;
void setCommittedSnapshot(const Timestamp& timestamp) final;
void setLocalSnapshot(const Timestamp& timestamp) final;
boost::optional<Timestamp> getLocalSnapshot() final;
void dropAllSnapshots() final;
//
// WT-specific methods
//
/**
* Starts a transaction and returns the SnapshotName used.
*
* Throws if there is currently no committed snapshot.
*/
Timestamp beginTransactionOnCommittedSnapshot(
WT_SESSION* session, WiredTigerBeginTxnBlock::IgnorePrepared ignorePrepared) const;
/**
* Starts a transaction on the last stable local timestamp, set by setLocalSnapshot.
*
* Throws if no local snapshot has been set.
*/
Timestamp beginTransactionOnLocalSnapshot(
WT_SESSION* session, WiredTigerBeginTxnBlock::IgnorePrepared ignorePrepared) const;
/**
* Returns lowest SnapshotName that could possibly be used by a future call to
* beginTransactionOnCommittedSnapshot, or boost::none if there is currently no committed
* snapshot.
*
* This should not be used for starting a transaction on this SnapshotName since the named
* snapshot may be deleted by the time you start the transaction.
*/
boost::optional<Timestamp> getMinSnapshotForNextCommittedRead() const;
private:
// Snapshot to use for reads at a commit timestamp.
mutable stdx::mutex _committedSnapshotMutex; // Guards _committedSnapshot.
boost::optional<Timestamp> _committedSnapshot;
// Snapshot to use for reads at a local stable timestamp.
mutable stdx::mutex _localSnapshotMutex; // Guards _localSnapshot.
boost::optional<Timestamp> _localSnapshot;
};
}
|