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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 <boost/optional.hpp>
#include "mongo/base/disallow_copying.h"
#include "mongo/s/request_types/shard_collection_gen.h"
#include "mongo/stdx/memory.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/concurrency/notification.h"
namespace mongo {
class OperationContext;
class ScopedShardCollection;
template <typename T>
class StatusWith;
/**
* Thread-safe object that keeps track of any active shardCollection commands running. There is only
* one instance of this object per shard.
*/
class ActiveShardCollectionRegistry {
MONGO_DISALLOW_COPYING(ActiveShardCollectionRegistry);
public:
ActiveShardCollectionRegistry();
~ActiveShardCollectionRegistry();
static ActiveShardCollectionRegistry& get(ServiceContext* service);
static ActiveShardCollectionRegistry& get(OperationContext* opCtx);
/**
* If the collection being requested to shard is not already being sharded on this shard,
* registers an active shardCollection with the specified arguments. Returns a
* ScopedShardCollection object, which must be signaled by the caller before it goes out of
* scope.
*
* If this collection is already being sharded on this shard and it has the exact same
* arguments, returns a ScopedShardCollection. The ScopedShardCollection can be used to join the
* already running shard collection.
*
* Otherwise returns a ConflictingOperationInProgress error.
*/
StatusWith<ScopedShardCollection> registerShardCollection(
const ShardsvrShardCollection& request);
private:
friend class ScopedShardCollection;
// Describes the state of a currently active shardCollection operation
struct ActiveShardCollectionState {
ActiveShardCollectionState(ShardsvrShardCollection inRequest)
: activeRequest(std::move(inRequest)),
notification(std::make_shared<Notification<Status>>()) {}
/**
* Constructs an error status to return in the case of conflicting operations.
*/
Status constructErrorStatus(const ShardsvrShardCollection& request) const;
// Exact arguments of the currently active operation
ShardsvrShardCollection activeRequest;
// Notification event that will be signaled when the currently active operation completes
std::shared_ptr<Notification<Status>> notification;
};
/**
* Unregisters a previously registered namespace with an ongoing shardCollection. Must only be
* called if a previous call to registerShardCollection has succeeded.
*/
void _clearShardCollection(std::string nss);
// Protects the state below
stdx::mutex _mutex;
// Map containing any collections currently being sharded
StringMap<ActiveShardCollectionState> _activeShardCollectionMap;
};
/**
* Object of this class is returned from the registerShardCollection call of the active shard
* collection registry. It can exist in two modes - 'execute' and 'join'. See the comments for
* registerShardCollection method for more details.
*/
class ScopedShardCollection {
MONGO_DISALLOW_COPYING(ScopedShardCollection);
public:
ScopedShardCollection(std::string nss,
ActiveShardCollectionRegistry* registry,
bool shouldExecute,
std::shared_ptr<Notification<Status>> completionNotification);
~ScopedShardCollection();
ScopedShardCollection(ScopedShardCollection&&);
ScopedShardCollection& operator=(ScopedShardCollection&&);
/**
* Returns true if the shardCollection object is in the 'execute' mode. This means that the
* caller can execute the shardCollection 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 is in the 'execute' mode when the shardCollection 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 shardCollection command calls signalComplete.
*/
Status waitForCompletion(OperationContext* opCtx);
private:
// Namespace of collection being sharded
std::string _nss;
// Registry from which to unregister the migration. Not owned.
ActiveShardCollectionRegistry* _registry;
/**
* Whether the holder is the first in line for a newly started shardCollection (in which case
* the destructor must unregister) or the caller is joining on an already-running
* shardCollection (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 shardCollection
std::shared_ptr<Notification<Status>> _completionNotification;
};
} // namespace mongo
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