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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/disallow_copying.h"
#include "mongo/s/request_types/move_primary_gen.h"
#include "mongo/util/concurrency/notification.h"
namespace mongo {
class ScopedMovePrimary;
/**
* Thread-safe object that keeps track of active movePrimary commands running on a node and limits
* them to only one per shard. There is only one instance of this object per shard.
*/
class ActiveMovePrimariesRegistry {
MONGO_DISALLOW_COPYING(ActiveMovePrimariesRegistry);
public:
ActiveMovePrimariesRegistry();
~ActiveMovePrimariesRegistry();
static ActiveMovePrimariesRegistry& get(ServiceContext* service);
static ActiveMovePrimariesRegistry& get(OperationContext* opCtx);
/**
* If there are no movePrimary operations running on this shard, registers an active
* movePrimary operation with the specified arguments. Returns a ScopedMovePrimary, which must
* be signaled by the caller before it goes out of scope.
*
* If there is an active movePrimary operation already running on this shard and it has the
* exact same arguments, returns a ScopedMovePrimary, which can be used to join the already
* running movePrimary command.
*
* Otherwise returns a ConflictingOperationInProgress error.
*/
StatusWith<ScopedMovePrimary> registerMovePrimary(const ShardMovePrimary& requestArgs);
/**
* If a movePrimary command has been previously registered through a call to
* registerMovePrimary, returns that namespace. Otherwise returns boost::none.
*/
boost::optional<NamespaceString> getActiveMovePrimaryNss();
private:
friend class ScopedMovePrimary;
// Describes the state of a current active movePrimary operation.
struct ActiveMovePrimaryState {
ActiveMovePrimaryState(ShardMovePrimary inRequestArgs)
: requestArgs(std::move(inRequestArgs)),
notification(std::make_shared<Notification<Status>>()) {}
/**
* Constructs an error status to return in the case of conflicting operations.
*/
Status constructErrorStatus() const;
// Exact arguments of the currently active operation
ShardMovePrimary requestArgs;
// Notification event, which will be signaled when the currently active operation completes
std::shared_ptr<Notification<Status>> notification;
};
/**
* Unregisters a previously registered namespace with an ongoing movePrimary operation. Must
* only be called if a previous call to registerMovePrimary has succeeded.
*/
void _clearMovePrimary();
// Protects the state below
stdx::mutex _mutex;
// If there is an active movePrimary operation going on, this field contains the request that
// initiated it.
boost::optional<ActiveMovePrimaryState> _activeMovePrimaryState;
};
/**
* An object of this class is returned from the registerMovePrimary call of the current active
* movePrimaries registry. It can exist in two modes - 'execute' and 'join.' See the comments for
* registerMovePrimary for more details.
*/
class ScopedMovePrimary {
MONGO_DISALLOW_COPYING(ScopedMovePrimary);
public:
ScopedMovePrimary(ActiveMovePrimariesRegistry* registry,
bool shouldExecute,
std::shared_ptr<Notification<Status>> completionNotification);
~ScopedMovePrimary();
ScopedMovePrimary(ScopedMovePrimary&&);
ScopedMovePrimary& operator=(ScopedMovePrimary&&);
/**
* Returns true if the registerMovePrimary object is in the 'execute' mode. This means that
* the registerMovePrimary object holder is next in line to execute the movePrimary command.
* The holder must execute the command and call signalComplete with a status.
*/
bool mustExecute() const {
return _shouldExecute;
}
/**
* Must only be called if the object was in the 'execute' mode when the movePrimary command
* was invoked (the command immediately executed). Signals any callers that might be blocked in
* waitForCompletion.
*/
void signalComplete(Status status);
/**
* Must only be called if the object is in the 'join' mode. Blocks until the main executor of
* the movePrimary command calls signalComplete.
*/
Status waitForCompletion(OperationContext* opCtx);
private:
// Registry from which to unregister the movePrimary. Not owned.
ActiveMovePrimariesRegistry* _registry;
/* Whether the holder is the first in line to call the movePrimary command (in which case the
* destructor must unregister) or the caller is joining on an already-running movePrimary
* operation (in which case the caller must block and wait for completion).
*/
bool _shouldExecute;
// This is the future, which will be signaled at the end of a movePrimary command.
std::shared_ptr<Notification<Status>> _completionNotification;
};
}
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