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/*
* Copyright (C) 2015 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/db/namespace_string.h"
#include "mongo/db/s/migration_source_manager.h"
#include "mongo/s/chunk_version.h"
namespace mongo {
class OperationContext;
/**
* A decoration on OperationContext representing per-operation shard version metadata sent to mongod
* from mongos as a command parameter.
*
* The metadata for a particular operation can be retrieved using the get() method.
*
* Note: This only supports storing the version for a single namespace.
*/
class OperationShardingState {
MONGO_DISALLOW_COPYING(OperationShardingState);
public:
class IgnoreVersioningBlock;
OperationShardingState();
/**
* Retrieves a reference to the shard version decorating the OperationContext, 'txn'.
*/
static OperationShardingState& get(OperationContext* txn);
/**
* Parses shard version from the command parameters 'cmdObj' and stores the results in this
* object along with the give namespace that is associated with the version. Does nothing
* if no shard version is attached to the command.
*
* Expects the format { ..., shardVersion: [<version>, <epoch>] }.
*
* This initialization may only be performed once for the lifetime of the object, which
* coincides with the lifetime of the request.
*/
void initializeShardVersion(NamespaceString nss, const BSONElement& shardVersionElement);
/**
* Returns whether or not there is a shard version associated with this operation.
*/
bool hasShardVersion() const;
/**
* Returns the shard version (i.e. maximum chunk version) of a namespace being used by the
* operation. Documents in chunks which did not belong on this shard at this shard version
* will be filtered out.
*
* Returns ChunkVersion::UNSHARDED() if this operation has no shard version information
* for the requested namespace.
*/
ChunkVersion getShardVersion(const NamespaceString& nss) const;
/**
* Stores the given chunk version of a namespace into this object.
*/
void setShardVersion(NamespaceString nss, ChunkVersion newVersion);
/**
* Undoes setting the shard version for the given namespace. Needed for views.
*/
void unsetShardVersion(NamespaceString nss);
/**
* This call is a no op if there isn't a currently active migration critical section. Otherwise
* it will wait for the critical section to complete up to the remaining operation time.
*
* Returns true if the call actually waited because of migration critical section (regardless if
* whether it timed out or not), false if there was no active migration critical section.
*/
bool waitForMigrationCriticalSectionSignal(OperationContext* txn);
/**
* Setting this value indicates that when the version check failed, there was an active
* migration for the namespace and that it would be prudent to wait for the critical section to
* complete before retrying so the router doesn't make wasteful requests.
*/
void setMigrationCriticalSectionSignal(std::shared_ptr<Notification<void>> critSecSignal);
private:
/**
* Resets this object back as if it was default constructed (ie _hasVersion is false,
* _shardVersion is UNSHARDED, _ns is empty).
*/
void _clear();
bool _hasVersion = false;
ChunkVersion _shardVersion{ChunkVersion::UNSHARDED()};
NamespaceString _ns;
// This value will only be non-null if version check during the operation execution failed due
// to stale version and there was a migration for that namespace, which was in critical section.
std::shared_ptr<Notification<void>> _migrationCriticalSectionSignal;
};
/**
* RAII type that sets the shard version for the current operation to IGNORED in its constructor,
* then restores the original version in its destructor. Used for temporarily disabling shard
* version checking for certain operations, such as multi-updates, that need to be unversioned
* but may be part of a larger group of operations with a single OperationContext where the other
* sub-operations might still require versioning.
*/
class OperationShardingState::IgnoreVersioningBlock {
MONGO_DISALLOW_COPYING(IgnoreVersioningBlock);
public:
IgnoreVersioningBlock(OperationContext* txn, const NamespaceString& ns);
~IgnoreVersioningBlock();
private:
OperationContext* _txn;
NamespaceString _ns;
ChunkVersion _originalVersion;
bool _hadOriginalVersion;
};
} // namespace mongo
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