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/**
* 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
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