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/**
* Copyright (C) 2019-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.
*/
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kReplication
#include "mongo/platform/basic.h"
#include "mongo/db/repl/split_horizon.h"
#include <utility>
#include "mongo/bson/util/bson_extract.h"
#include "mongo/db/client.h"
using namespace std::literals::string_literals;
using std::begin;
using std::end;
namespace mongo {
namespace repl {
namespace {
const auto getSplitHorizonParameters = Client::declareDecoration<SplitHorizon::Parameters>();
using AllMappings = SplitHorizon::AllMappings;
// The reverse mappings for a forward mapping are used to fully initialize a `SplitHorizon`
// instance.
AllMappings computeReverseMappings(SplitHorizon::ForwardMapping forwardMapping) {
using ForwardMapping = SplitHorizon::ForwardMapping;
using ReverseHostOnlyMapping = SplitHorizon::ReverseHostOnlyMapping;
// Build the reverse mapping (from host-only to horizon names) from the forward mapping table.
ReverseHostOnlyMapping reverseHostMapping;
// Default horizon case is special -- it always has to exist, and needs to be set before
// entering the loop, to correctly handle ambiguous host-only cases within that horizon.
reverseHostMapping.emplace(forwardMapping[SplitHorizon::kDefaultHorizon].host(),
std::string{SplitHorizon::kDefaultHorizon});
for (const auto& entry : forwardMapping) {
reverseHostMapping[entry.second.host()] = entry.first;
}
// Check for duplicate host-and-port entries.
if (forwardMapping.size() != reverseHostMapping.size()) {
const auto horizonMember = [&] {
std::vector<std::string> rv;
std::transform(begin(forwardMapping),
end(forwardMapping),
back_inserter(rv),
[](const auto& entry) { return entry.second.host(); });
std::sort(begin(rv), end(rv));
return rv;
}();
auto duplicate = std::adjacent_find(begin(horizonMember), end(horizonMember));
invariant(duplicate != end(horizonMember));
uasserted(ErrorCodes::BadValue, "Duplicate horizon member found \""s + *duplicate + "\".");
}
return {std::move(forwardMapping), std::move(reverseHostMapping)};
}
SplitHorizon::ForwardMapping computeForwardMappings(
const HostAndPort& host, const boost::optional<BSONObj>& horizonsObject) {
SplitHorizon::ForwardMapping forwardMapping;
if (horizonsObject) {
using MapMember = std::pair<std::string, HostAndPort>;
if (horizonsObject->isEmpty()) {
uasserted(ErrorCodes::BadValue,
str::stream() << "The horizons field cannot be empty, if present.");
}
// Process all of the BSON description of horizons into a linear list.
auto convert = [](auto&& horizonObj) -> MapMember {
const StringData horizonName = horizonObj.fieldName();
if (horizonObj.type() != String) {
uasserted(ErrorCodes::TypeMismatch,
str::stream() << "horizons." << horizonName
<< " field has non-string value of type "
<< typeName(horizonObj.type()));
} else if (horizonName == SplitHorizon::kDefaultHorizon) {
uasserted(ErrorCodes::BadValue,
"Horizon name \"" + SplitHorizon::kDefaultHorizon +
"\" is reserved for internal mongodb usage");
} else if (horizonName == "") {
uasserted(ErrorCodes::BadValue, "Horizons cannot have empty names");
}
return {horizonName.toString(), HostAndPort{horizonObj.valueStringData()}};
};
const auto horizonEntries = [&] {
std::vector<MapMember> rv;
std::transform(
begin(*horizonsObject), end(*horizonsObject), inserter(rv, end(rv)), convert);
return rv;
}();
// Dump the linear list into the forward mapping.
forwardMapping.insert(begin(horizonEntries), end(horizonEntries));
// Check for duplicate horizon names and reserved names, which would be if the horizon
// linear list size disagrees with the size of the mapping.
if (horizonEntries.size() != forwardMapping.size()) {
// If the map has a different amount than a linear list of the bson converted, then it
// had better be a lesser amount, indicating duplicates. A greater amount should be
// impossible.
invariant(horizonEntries.size() > forwardMapping.size());
// Find which one is duplicated.
const auto horizonNames = [&] {
std::vector<std::string> rv;
std::transform(begin(horizonEntries),
end(horizonEntries),
back_inserter(rv),
[](const auto& entry) { return entry.first; });
std::sort(begin(rv), end(rv));
return rv;
}();
const auto duplicate = std::adjacent_find(begin(horizonNames), end(horizonNames));
// Report our duplicate if found.
if (duplicate != end(horizonNames)) {
uasserted(ErrorCodes::BadValue,
"Duplicate horizon name found \""s + *duplicate + "\".");
}
}
}
// Finally add the default mapping, regardless of whether we processed a configuration.
const bool successInDefaultPlacement =
forwardMapping.emplace(SplitHorizon::kDefaultHorizon, host).second;
// And that insertion BETTER succeed -- it mightn't if there's a bug in the configuration
// processing logic.
invariant(successInDefaultPlacement);
return forwardMapping;
}
} // namespace
void SplitHorizon::setParameters(Client* const client, boost::optional<std::string> sniName) {
stdx::lock_guard<Client> lk(*client);
getSplitHorizonParameters(*client) = Parameters{std::move(sniName)};
}
auto SplitHorizon::getParameters(const Client* const client) -> Parameters {
return getSplitHorizonParameters(*client);
}
StringData SplitHorizon::determineHorizon(const SplitHorizon::Parameters& horizonParameters) const {
if (horizonParameters.sniName) {
const auto sniName = *horizonParameters.sniName;
const auto found = _reverseHostMapping.find(sniName);
if (found != end(_reverseHostMapping)) {
return found->second;
}
}
return kDefaultHorizon;
}
void SplitHorizon::toBSON(BSONObjBuilder& configBuilder) const {
invariant(!_forwardMapping.empty());
invariant(_forwardMapping.count(SplitHorizon::kDefaultHorizon));
// `forwardMapping` should always contain the "__default" horizon, so we need to emit the
// horizon repl specification only when there are OTHER horizons besides it. If there's only
// one horizon, it's gotta be "__default", so we do nothing.
if (_forwardMapping.size() == 1)
return;
// StringMaps are iterated in arbitrary order, so we sort before returning the horizons.
std::vector<std::pair<StringData, std::string>> sortedHorizons;
for (const auto& horizon : _forwardMapping) {
// The "__default" horizon should never be emitted in the horizon table.
if (horizon.first == SplitHorizon::kDefaultHorizon)
continue;
sortedHorizons.emplace_back(horizon.first, horizon.second.toString());
}
std::sort(sortedHorizons.begin(), sortedHorizons.end());
BSONObjBuilder horizonsBson(configBuilder.subobjStart("horizons"));
for (const auto& horizon : sortedHorizons) {
horizonsBson.append(horizon.first, horizon.second);
}
}
// A split horizon built from a known forward mapping table should just need to construct the
// reverse mappings.
SplitHorizon::SplitHorizon(ForwardMapping mapping)
: SplitHorizon(computeReverseMappings(std::move(mapping))) {}
// A split horizon constructed from the BSON configuration and the host specifier for this member
// needs to compute the forward mapping table. In turn that will be used to compute the reverse
// mapping table.
SplitHorizon::SplitHorizon(const HostAndPort& host, const boost::optional<BSONObj>& horizonsObject)
: SplitHorizon(computeForwardMappings(host, horizonsObject)) {}
} // namespace repl
} // namespace mongo
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