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
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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 "mongo/s/database_version_gen.h"
namespace mongo {
/**
* This class is used to represent a specific version of a Database.
*
* Currently it is implemented as a (uuid, [timestamp,] lastMod) triplet, where the
* timestamp is optional in versions prior 4.9. The uuid is going to be removed soon,
* since they are not comparable (that's the reason why there is a ComparableDatabaseVersion class).
*
* Once uuids are gone, relational operators should be implemented in this class.
*
*/
class DatabaseVersion : private DatabaseVersionBase {
public:
using DatabaseVersionBase::getLastMod;
using DatabaseVersionBase::toBSON;
// It returns a new DatabaseVersion marked as fixed. A fixed database version is used to
// distinguish databases that do not have entries in the sharding catalog, such as 'config' and
// 'admin'
static DatabaseVersion makeFixed();
DatabaseVersion() = default;
explicit DatabaseVersion(const BSONObj& obj) {
DatabaseVersionBase::parseProtected(IDLParserErrorContext("DatabaseVersion"), obj);
}
/**
* Constructor of a DatabaseVersion based on epochs
*/
explicit DatabaseVersion(mongo::UUID uuid)
: DatabaseVersion(uuid, boost::none /* timestamp */) {}
/**
* Constructor of a DatabaseVersion based on epochs and timestamps
*/
DatabaseVersion(mongo::UUID uuid, boost::optional<mongo::Timestamp> timestamp)
: DatabaseVersionBase(1 /* lastMod */) {
setUuid(uuid);
setTimestamp(timestamp);
}
DatabaseVersion makeUpdated() const;
bool operator==(const DatabaseVersion& other) const {
return getUuid() == other.getUuid() && getLastMod() == other.getLastMod();
}
bool operator!=(const DatabaseVersion& other) const {
return !(*this == other);
}
bool isFixed() const {
return getLastMod() == 0;
}
mongo::UUID getUuid() const {
return *DatabaseVersionBase::getUuid();
}
};
/**
* The DatabaseVersion class contains a UUID that is not comparable,
* in fact is impossible to compare two different DatabaseVersion that have different UUIDs.
*
* This class wrap a DatabaseVersion object to make it always comparable by timestamping it with a
* node-local sequence number (_uuidDisambiguatingSequenceNum).
*
* This class class should go away once a cluster-wide comparable DatabaseVersion will be
* implemented.
*/
class ComparableDatabaseVersion {
public:
/**
* Creates a ComparableDatabaseVersion that wraps the given DatabaseVersion.
* Each object created through this method will have a local sequence number greater than the
* previously created ones.
*/
static ComparableDatabaseVersion makeComparableDatabaseVersion(const DatabaseVersion& version);
/**
* Empty constructor needed by the ReadThroughCache.
*
* Instances created through this constructor will be always less then the ones created through
* the static constructor.
*/
ComparableDatabaseVersion() = default;
const DatabaseVersion& getVersion() const {
return *_dbVersion;
}
BSONObj toBSONForLogging() const;
bool operator==(const ComparableDatabaseVersion& other) const;
bool operator!=(const ComparableDatabaseVersion& other) const {
return !(*this == other);
}
/**
* In case the two compared instances have different UUIDs, the most recently created one will
* be greater, otherwise the comparison will be driven by the lastMod field of the underlying
* DatabaseVersion.
*/
bool operator<(const ComparableDatabaseVersion& other) const;
bool operator>(const ComparableDatabaseVersion& other) const {
return other < *this;
}
bool operator<=(const ComparableDatabaseVersion& other) const {
return !(*this > other);
}
bool operator>=(const ComparableDatabaseVersion& other) const {
return !(*this < other);
}
private:
static AtomicWord<uint64_t> _uuidDisambiguatingSequenceNumSource;
ComparableDatabaseVersion(const DatabaseVersion& version,
uint64_t uuidDisambiguatingSequenceNum)
: _dbVersion(version), _uuidDisambiguatingSequenceNum(uuidDisambiguatingSequenceNum) {}
boost::optional<DatabaseVersion> _dbVersion;
// Locally incremented sequence number that allows to compare two database versions with
// different UUIDs. Each new comparableDatabaseVersion will have a greater sequence number then
// the ones created before.
uint64_t _uuidDisambiguatingSequenceNum{0};
};
} // namespace mongo
|
