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/**
* Copyright (C) 2017 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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kDefault
#include "mongo/platform/basic.h"
#include "mongo/db/logical_clock.h"
#include "mongo/base/status.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/server_parameters.h"
#include "mongo/db/service_context.h"
#include "mongo/db/time_proof_service.h"
#include "mongo/util/log.h"
namespace mongo {
constexpr Seconds LogicalClock::kMaxAcceptableLogicalClockDriftSecs;
server_parameter_storage_type<long long, ServerParameterType::kStartupOnly>::value_type
maxAcceptableLogicalClockDriftSecs(LogicalClock::kMaxAcceptableLogicalClockDriftSecs.count());
class MaxAcceptableLogicalClockDriftSecs
: public ExportedServerParameter<long long, ServerParameterType::kStartupOnly> {
public:
MaxAcceptableLogicalClockDriftSecs()
: ExportedServerParameter<long long, ServerParameterType::kStartupOnly>(
ServerParameterSet::getGlobal(),
"maxAcceptableLogicalClockDriftSecs",
&maxAcceptableLogicalClockDriftSecs) {}
Status validate(const long long& potentialNewValue) {
if (potentialNewValue <= 0) {
return Status(ErrorCodes::BadValue,
str::stream() << "maxAcceptableLogicalClockDriftSecs must be positive, "
"but attempted to set to: "
<< potentialNewValue);
}
return Status::OK();
}
} maxAcceptableLogicalClockDriftSecsParameter;
namespace {
const auto getLogicalClock = ServiceContext::declareDecoration<std::unique_ptr<LogicalClock>>();
bool lessThanOrEqualToMaxPossibleTime(LogicalTime time, uint64_t nTicks) {
return time.asTimestamp().getSecs() <= LogicalClock::kMaxSignedInt &&
time.asTimestamp().getInc() <= (LogicalClock::kMaxSignedInt - nTicks);
}
}
LogicalClock* LogicalClock::get(ServiceContext* service) {
return getLogicalClock(service).get();
}
LogicalClock* LogicalClock::get(OperationContext* ctx) {
return get(ctx->getClient()->getServiceContext());
}
void LogicalClock::set(ServiceContext* service, std::unique_ptr<LogicalClock> clockArg) {
auto& clock = getLogicalClock(service);
clock = std::move(clockArg);
}
LogicalClock::LogicalClock(ServiceContext* service) : _service(service) {}
LogicalTime LogicalClock::getClusterTime() {
stdx::lock_guard<stdx::mutex> lock(_mutex);
return _clusterTime;
}
Status LogicalClock::advanceClusterTime(const LogicalTime newTime) {
stdx::lock_guard<stdx::mutex> lock(_mutex);
auto rateLimitStatus = _passesRateLimiter_inlock(newTime);
if (!rateLimitStatus.isOK()) {
return rateLimitStatus;
}
if (newTime > _clusterTime) {
_clusterTime = newTime;
}
return Status::OK();
}
LogicalTime LogicalClock::reserveTicks(uint64_t nTicks) {
invariant(nTicks > 0 && nTicks <= kMaxSignedInt);
stdx::lock_guard<stdx::mutex> lock(_mutex);
LogicalTime clusterTime = _clusterTime;
const unsigned wallClockSecs =
durationCount<Seconds>(_service->getFastClockSource()->now().toDurationSinceEpoch());
unsigned clusterTimeSecs = clusterTime.asTimestamp().getSecs();
// Synchronize clusterTime with wall clock time, if clusterTime was behind in seconds.
if (clusterTimeSecs < wallClockSecs) {
clusterTime = LogicalTime(Timestamp(wallClockSecs, 0));
}
// If reserving 'nTicks' would force the cluster timestamp's increment field to exceed (2^31-1),
// overflow by moving to the next second. We use the signed integer maximum as an overflow point
// in order to preserve compatibility with potentially signed or unsigned integral Timestamp
// increment types. It is also unlikely to apply more than 2^31 oplog entries in the span of one
// second.
else if (clusterTime.asTimestamp().getInc() > (kMaxSignedInt - nTicks)) {
log() << "Exceeded maximum allowable increment value within one second. Moving clusterTime "
"forward to the next second.";
// Move time forward to the next second
clusterTime = LogicalTime(Timestamp(clusterTime.asTimestamp().getSecs() + 1, 0));
}
uassert(40482,
"cluster time cannot be advanced beyond its maximum value",
lessThanOrEqualToMaxPossibleTime(clusterTime, nTicks));
// Save the next cluster time.
clusterTime.addTicks(1);
_clusterTime = clusterTime;
// Add the rest of the requested ticks if needed.
if (nTicks > 1) {
_clusterTime.addTicks(nTicks - 1);
}
return clusterTime;
}
void LogicalClock::setClusterTimeFromTrustedSource(LogicalTime newTime) {
stdx::lock_guard<stdx::mutex> lock(_mutex);
// Rate limit checks are skipped here so a server with no activity for longer than
// maxAcceptableLogicalClockDriftSecs seconds can still have its cluster time initialized.
uassert(40483,
"cluster time cannot be advanced beyond its maximum value",
lessThanOrEqualToMaxPossibleTime(newTime, 0));
if (newTime > _clusterTime) {
_clusterTime = newTime;
}
}
Status LogicalClock::_passesRateLimiter_inlock(LogicalTime newTime) {
const unsigned wallClockSecs =
durationCount<Seconds>(_service->getFastClockSource()->now().toDurationSinceEpoch());
auto maxAcceptableDriftSecs = static_cast<const unsigned>(maxAcceptableLogicalClockDriftSecs);
auto newTimeSecs = newTime.asTimestamp().getSecs();
// Both values are unsigned, so compare them first to avoid wrap-around.
if ((newTimeSecs > wallClockSecs) && (newTimeSecs - wallClockSecs) > maxAcceptableDriftSecs) {
return Status(ErrorCodes::ClusterTimeFailsRateLimiter,
str::stream() << "New cluster time, " << newTimeSecs
<< ", is too far from this node's wall clock time, "
<< wallClockSecs
<< ".");
}
uassert(40484,
"cluster time cannot be advanced beyond its maximum value",
lessThanOrEqualToMaxPossibleTime(newTime, 0));
return Status::OK();
}
} // namespace mongo
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