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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.
*/
#pragma once
#include "mongo/db/clientcursor.h"
#include "mongo/util/elapsed_tracker.h"
namespace mongo {
class RunnerYieldPolicy {
public:
RunnerYieldPolicy() : _elapsedTracker(128, 10), _runnerYielding(NULL) { }
~RunnerYieldPolicy() {
if (NULL != _runnerYielding) {
// We were destructed mid-yield. Since we're being used to yield a runner, we have
// to deregister the runner.
ClientCursor::deregisterRunner(_runnerYielding);
}
}
bool shouldYield() {
return _elapsedTracker.intervalHasElapsed();
}
/**
* Yield the provided runner, registering and deregistering it appropriately. Deal with
* deletion during a yield by setting _runnerYielding to ensure deregistration.
*
* Provided runner MUST be YIELD_MANUAL.
*/
bool yieldAndCheckIfOK(Runner* runner) {
verify(runner);
int micros = ClientCursor::suggestYieldMicros();
// No point in yielding.
if (micros <= 0) { return true; }
// If micros > 0, we should yield.
runner->saveState();
_runnerYielding = runner;
ClientCursor::registerRunner(_runnerYielding);
staticYield(micros, NULL);
ClientCursor::deregisterRunner(_runnerYielding);
_runnerYielding = NULL;
_elapsedTracker.resetLastTime();
return runner->restoreState();
}
/**
* Yield, possibly fetching the provided record. Caller is in charge of all runner
* registration.
*
* Used for YIELD_AUTO runners.
*/
void yield(Record* rec = NULL) {
int micros = ClientCursor::suggestYieldMicros();
if (micros > 0) {
staticYield(micros, rec);
_elapsedTracker.resetLastTime();
}
}
static void staticYield(int micros, Record* rec = NULL) {
ClientCursor::staticYield(micros, "", rec);
}
private:
ElapsedTracker _elapsedTracker;
Runner* _runnerYielding;
};
} // namespace mongo
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