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/**
* Copyright (C) 2016 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 <boost/optional.hpp>
#include "mongo/base/disallow_copying.h"
#include "mongo/bson/oid.h"
#include "mongo/db/repl/read_concern_args.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
class OperationContext;
class ServiceContext;
template <typename T>
class StatusWith;
/**
* Decoration on ServiceContext used by any process in a sharded cluster to access the cluster ID.
*/
class ClusterIdentityLoader {
MONGO_DISALLOW_COPYING(ClusterIdentityLoader);
public:
ClusterIdentityLoader() = default;
~ClusterIdentityLoader() = default;
/**
* Retrieves the ClusterIdentity object associated with the given service context.
*/
static ClusterIdentityLoader* get(ServiceContext* serviceContext);
static ClusterIdentityLoader* get(OperationContext* operationContext);
/*
* Returns the cached cluster ID. Invalid to call unless loadClusterId has previously been
* called and returned success.
*/
OID getClusterId();
/**
* Loads the cluster ID from the config server's config.version collection and stores it into
* _lastLoadResult. If the cluster ID has previously been successfully loaded, this is a no-op.
* If another thread is already in the process of loading the cluster ID, concurrent calls will
* wait for that thread to finish and then return its results.
*/
Status loadClusterId(OperationContext* opCtx, const repl::ReadConcernLevel& readConcernLevel);
/**
* Called if the config.version document is rolled back. Notifies the ClusterIdentityLoader
* that the cached cluster ID is invalid and needs to be reloaded.
*/
void discardCachedClusterId();
private:
enum class InitializationState {
kUninitialized, // We have never successfully loaded the cluster ID
kLoading, // One thread is in the process of attempting to load the cluster ID
kInitialized, // We have been able to successfully load the cluster ID.
};
/**
* Queries the config.version collection on the config server, extracts the cluster ID from
* the version document, and returns it.
*/
StatusWith<OID> _fetchClusterIdFromConfig(OperationContext* opCtx,
const repl::ReadConcernLevel& readConcernLevel);
stdx::mutex _mutex;
stdx::condition_variable _inReloadCV;
// Used to ensure that only one thread at a time attempts to reload the cluster ID from the
// config.version collection
InitializationState _initializationState{InitializationState::kUninitialized};
// Stores the result of the last call to _loadClusterId. Used to cache the cluster ID once it
// has been successfully loaded, as well as to report failures in loading across threads.
StatusWith<OID> _lastLoadResult{Status{ErrorCodes::InternalError, "cluster ID never loaded"}};
};
} // namespace mongo
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