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/**
* Copyright (C) 2018 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.
*/
#pragma once
#include "mongo/db/curop.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_record_store.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h"
#include "mongo/util/fail_point_service.h"
namespace mongo {
// When set, returns simulates returning WT_PREPARE_CONFLICT on WT cursor read operations.
MONGO_FAIL_POINT_DECLARE(WTPrepareConflictForReads);
/**
* Logs a message with the number of prepare conflict retry attempts.
*/
void wiredTigerPrepareConflictLog(int attempt);
/**
* Runs the argument function f as many times as needed for f to return an error other than
* WT_PREPARE_CONFLICT. Each time f returns WT_PREPARE_CONFLICT we wait until the current unit of
* work commits or aborts, and then try f again. Imposes no upper limit on the number of times to
* re-try f, so any required timeout behavior must be enforced within f.
* The function f must return a WiredTiger error code.
*/
template <typename F>
int wiredTigerPrepareConflictRetry(OperationContext* opCtx, F&& f) {
invariant(opCtx);
auto recoveryUnit = WiredTigerRecoveryUnit::get(opCtx);
int attempts = 0;
while (true) {
attempts++;
// If the failpoint is enabled, don't call the function, just simulate a conflict.
int ret =
MONGO_FAIL_POINT(WTPrepareConflictForReads) ? WT_PREPARE_CONFLICT : WT_READ_CHECK(f());
if (ret != WT_PREPARE_CONFLICT)
return ret;
CurOp::get(opCtx)->debug().additiveMetrics.incrementPrepareReadConflicts(1);
wiredTigerPrepareConflictLog(attempts);
// Wait on the session cache to signal that a unit of work has been committed or aborted.
recoveryUnit->getSessionCache()->waitUntilPreparedUnitOfWorkCommitsOrAborts(opCtx);
}
}
} // namespace mongo
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