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/**
* Copyright (C) 2018-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.
*/
#pragma once
#include "mongo/base/string_data.h"
#include "mongo/db/service_context.h"
#include "mongo/platform/mutex.h"
#include "mongo/stdx/condition_variable.h"
namespace mongo {
/**
* Service to manage DDL locks.
*/
class DDLLockManager {
public:
// Default timeout which will be used if one is not passed to the lock method.
static const Minutes kDefaultLockTimeout;
// Timeout value, which specifies that if the lock is not available immediately, no attempt
// should be made to wait for it to become free.
static const Milliseconds kSingleLockAttemptTimeout;
/**
* RAII type for the DDL lock.
*/
class ScopedLock {
ScopedLock(const ScopedLock&) = delete;
ScopedLock& operator=(const ScopedLock&) = delete;
public:
ScopedLock(StringData lockName, StringData reason, DDLLockManager* lockManager);
~ScopedLock();
ScopedLock(ScopedLock&& other);
StringData getNs() {
return _ns;
}
StringData getReason() {
return _reason;
}
private:
std::string _ns;
std::string _reason;
DDLLockManager* _lockManager;
};
DDLLockManager() = default;
~DDLLockManager() = default;
/**
* Retrieves the DDLLockManager singleton.
*/
static DDLLockManager* get(ServiceContext* service);
static DDLLockManager* get(OperationContext* opCtx);
/**
* Returns a RAII style lock on the given namespace @ns.
*
* @ns Namespace to lock (both database and collections).
* @reason Reson for which the lock is being acquired (e.g. 'createCollection').
* @timeout Time after which this acquisition attempt will give up in case of lock contention.
* A timeout value of -1 means the acquisition will be retried forever.
*
*
* Throws ErrorCodes::LockBusy in case the timeout is reached.
* Throws ErrorCategory::Interruption in case the opeartion context is interrupted.
*/
ScopedLock lock(OperationContext* opCtx,
StringData ns,
StringData reason,
Milliseconds timeout);
protected:
struct NSLock {
NSLock(StringData reason) : reason(reason.toString()) {}
stdx::condition_variable cvLocked;
int numWaiting = 1;
bool isInProgress = true;
std::string reason;
};
Mutex _mutex = MONGO_MAKE_LATCH("DDLLockManager::_mutex");
StringMap<std::shared_ptr<NSLock>> _inProgressMap;
};
} // namespace mongo
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