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/**
* Copyright (C) 2013 10gen 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/db/query/plan_yield_policy.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/curop.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/query/query_knobs.h"
#include "mongo/db/query/query_yield.h"
namespace mongo {
PlanYieldPolicy::PlanYieldPolicy(PlanExecutor* exec, PlanExecutor::YieldPolicy policy)
: _policy(policy),
_forceYield(false),
_elapsedTracker(internalQueryExecYieldIterations, internalQueryExecYieldPeriodMS),
_planYielding(exec) {}
bool PlanYieldPolicy::shouldYield() {
if (!allowedToYield())
return false;
invariant(!_planYielding->getOpCtx()->lockState()->inAWriteUnitOfWork());
if (_forceYield)
return true;
return _elapsedTracker.intervalHasElapsed();
}
void PlanYieldPolicy::resetTimer() {
_elapsedTracker.resetLastTime();
}
bool PlanYieldPolicy::yield(RecordFetcher* fetcher) {
invariant(_planYielding);
invariant(allowedToYield());
_forceYield = false;
OperationContext* opCtx = _planYielding->getOpCtx();
invariant(opCtx);
invariant(!opCtx->lockState()->inAWriteUnitOfWork());
// Can't use MONGO_WRITE_CONFLICT_RETRY_LOOP_BEGIN/END since we need to call saveState
// before reseting the transaction.
for (int attempt = 1; true; attempt++) {
try {
// All YIELD_AUTO plans will get here eventually when the elapsed tracker triggers
// that it's time to yield. Whether or not we will actually yield, we need to check
// if this operation has been interrupted. Throws if the interrupt flag is set.
if (_policy == PlanExecutor::YIELD_AUTO) {
opCtx->checkForInterrupt();
}
// No need to yield if the collection is NULL.
if (NULL == _planYielding->collection()) {
return true;
}
try {
_planYielding->saveState();
} catch (const WriteConflictException& wce) {
invariant(!"WriteConflictException not allowed in saveState");
}
if (_policy == PlanExecutor::WRITE_CONFLICT_RETRY_ONLY) {
// Just reset the snapshot. Leave all LockManager locks alone.
opCtx->recoveryUnit()->abandonSnapshot();
} else {
// Release and reacquire locks.
QueryYield::yieldAllLocks(opCtx, fetcher);
}
return _planYielding->restoreStateWithoutRetrying(opCtx);
} catch (const WriteConflictException& wce) {
CurOp::get(opCtx)->debug().writeConflicts++;
WriteConflictException::logAndBackoff(
attempt, "plan execution restoreState", _planYielding->collection()->ns().ns());
// retry
}
}
}
} // namespace mongo
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