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
172
173
174
175
176
177
178
179
|
/**
* 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.
*/
#include "mongo/platform/basic.h"
#include "mongo/client/read_preference.h"
#include <string>
#include "mongo/base/status.h"
#include "mongo/base/status_with.h"
#include "mongo/base/string_data.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/bson/bsontypes.h"
#include "mongo/bson/util/bson_extract.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/mongoutils/str.h"
namespace mongo {
namespace {
const char kModeFieldName[] = "mode";
const char kTagsFieldName[] = "tags";
const char kPrimaryOnly[] = "primary";
const char kPrimaryPreferred[] = "primaryPreferred";
const char kSecondaryOnly[] = "secondary";
const char kSecondaryPreferred[] = "secondaryPreferred";
const char kNearest[] = "nearest";
StringData readPreferenceName(ReadPreference pref) {
switch (pref) {
case ReadPreference::PrimaryOnly:
return StringData(kPrimaryOnly);
case ReadPreference::PrimaryPreferred:
return StringData(kPrimaryPreferred);
case ReadPreference::SecondaryOnly:
return StringData(kSecondaryOnly);
case ReadPreference::SecondaryPreferred:
return StringData(kSecondaryPreferred);
case ReadPreference::Nearest:
return StringData(kNearest);
default:
MONGO_UNREACHABLE;
}
}
StatusWith<ReadPreference> parseReadPreferenceMode(StringData prefStr) {
if (prefStr == kPrimaryOnly) {
return ReadPreference::PrimaryOnly;
} else if (prefStr == kPrimaryPreferred) {
return ReadPreference::PrimaryPreferred;
} else if (prefStr == kSecondaryOnly) {
return ReadPreference::SecondaryOnly;
} else if (prefStr == kSecondaryPreferred) {
return ReadPreference::SecondaryPreferred;
} else if (prefStr == kNearest) {
return ReadPreference::Nearest;
}
return Status(ErrorCodes::FailedToParse,
str::stream() << "Could not parse $readPreference mode '" << prefStr
<< "'. Only the modes '" << kPrimaryOnly << "', '"
<< kPrimaryPreferred << "', " << kSecondaryOnly << "', '"
<< kSecondaryPreferred << "', and '" << kNearest
<< "' are supported.");
}
// Slight kludge here: if we weren't passed a TagSet, we default to the empty
// TagSet if ReadPreference is Primary, or the default (wildcard) TagSet otherwise.
// This maintains compatibility with existing code, while preserving the ability to round
// trip.
TagSet defaultTagSetForMode(ReadPreference mode) {
switch (mode) {
case ReadPreference::PrimaryOnly:
return TagSet::primaryOnly();
default:
return TagSet();
}
}
} // namespace
TagSet::TagSet() : _tags(BSON_ARRAY(BSONObj())) {}
TagSet TagSet::primaryOnly() {
return TagSet{BSONArray()};
}
ReadPreferenceSetting::ReadPreferenceSetting(ReadPreference pref, TagSet tags)
: pref(std::move(pref)), tags(std::move(tags)) {}
ReadPreferenceSetting::ReadPreferenceSetting(ReadPreference pref)
: ReadPreferenceSetting(pref, defaultTagSetForMode(pref)) {}
StatusWith<ReadPreferenceSetting> ReadPreferenceSetting::fromBSON(const BSONObj& readPrefObj) {
std::string modeStr;
auto modeExtractStatus = bsonExtractStringField(readPrefObj, kModeFieldName, &modeStr);
if (!modeExtractStatus.isOK()) {
return modeExtractStatus;
}
ReadPreference mode;
auto swReadPrefMode = parseReadPreferenceMode(modeStr);
if (!swReadPrefMode.isOK()) {
return swReadPrefMode.getStatus();
}
mode = std::move(swReadPrefMode.getValue());
TagSet tags;
BSONElement tagsElem;
auto tagExtractStatus =
bsonExtractTypedField(readPrefObj, kTagsFieldName, mongo::Array, &tagsElem);
if (tagExtractStatus.isOK()) {
tags = TagSet{BSONArray(tagsElem.Obj().getOwned())};
// In accordance with the read preference spec, passing the default wildcard tagset
// '[{}]' is the same as not passing a TagSet at all. Furthermore, passing an empty
// TagSet with a non-primary ReadPreference is equivalent to passing the wildcard
// ReadPreference.
if (tags == TagSet() || tags == TagSet::primaryOnly()) {
tags = defaultTagSetForMode(mode);
}
// If we are using a user supplied TagSet, check that it is compatible with
// the readPreference mode.
else if (ReadPreference::PrimaryOnly == mode && (tags != TagSet::primaryOnly())) {
return Status(ErrorCodes::BadValue,
"Only empty tags are allowed with primary read preference");
}
}
else if (ErrorCodes::NoSuchKey == tagExtractStatus) {
tags = defaultTagSetForMode(mode);
} else {
return tagExtractStatus;
}
return ReadPreferenceSetting(mode, tags);
}
BSONObj ReadPreferenceSetting::toBSON() const {
BSONObjBuilder bob;
bob.append(kModeFieldName, readPreferenceName(pref));
if (tags != defaultTagSetForMode(pref)) {
bob.append(kTagsFieldName, tags.getTagBSON());
}
return bob.obj();
}
std::string ReadPreferenceSetting::toString() const {
return toBSON().toString();
}
} // namespace mongo
|