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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/db/logical_time.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/s/scoped_collection_metadata.h"
#include "mongo/db/s/sharding_migration_critical_section.h"
#include "mongo/db/s/sharding_state_lock.h"
namespace mongo {
/**
* Each collection on a mongod instance is dynamically assigned an implementation of
* CollectionShardingState for the duration of its lifetime, which represents the
* shard's knowledge of its the shard version and the set of chunks that it owns, as well as
* functions for updating and tracking this state.
*
* On shard servers, the implementation used is CollectionShardingRuntime.
*
* On embedded or non-shard servers, the implementation used is CollectionShardingStateStandalone,
* which is a mostly empty implementation.
*
* This separation was required for linking reasons and the difference between sharded and not
* sharded clusters.
*
* The CollectionShardingStateFactory class below is used to instantiate the correct subclass of
* CollectionShardingState at runtime.
*
* Synchronization rule: In order to obtain an instance of this object, the caller must have some
* lock on the respective collection. Different functions require different lock levels though, so
* be sure to check the function-level comments for details.
*/
class CollectionShardingState {
public:
CollectionShardingState() = default;
virtual ~CollectionShardingState() = default;
CollectionShardingState(const CollectionShardingState&) = delete;
CollectionShardingState& operator=(const CollectionShardingState&) = delete;
/**
* Obtains the sharding state for the specified collection. If it does not exist, it will be
* created and will remain in memory until the collection is dropped.
*
* Must be called with some lock held on the specific collection being looked up and the
* returned pointer must not be stored.
*/
static CollectionShardingState* get(OperationContext* opCtx, const NamespaceString& nss);
/**
* It is the caller's responsibility to ensure that the collection locks for this namespace are
* held when this is called. The returned pointer should never be stored.
*/
static CollectionShardingState* get_UNSAFE(ServiceContext* svcCtx, const NamespaceString& nss);
/**
* Reports all collections which have filtering information associated.
*/
static void report(OperationContext* opCtx, BSONObjBuilder* builder);
/**
* Returns the chunk filtering object that the current operation should be using for
* the collection.
*
* If the operation context contains an 'atClusterTime', the returned filtering object will be
* tied to a specific point in time. Otherwise, it will reference the latest time available. If
* the operation is not associated with a shard version (refer to
* OperationShardingState::isOperationVersioned for more info on that), returns an UNSHARDED
* metadata object.
*
* The intended users of this method are callers which need to perform filtering. Use
* 'getCurrentMetadata' for other cases, like obtaining information about sharding-related
* properties of the collection are necessary that won't change under collection IX/IS lock
* (e.g., isSharded or the shard key).
*
* The returned object is safe to access even after the collection lock has been dropped.
*/
virtual ScopedCollectionFilter getOwnershipFilter(OperationContext* opCtx,
bool isCollection) = 0;
/**
* See the comments for 'getOwnershipFilter' above for more information on this method.
*/
virtual ScopedCollectionMetadata getCurrentMetadata() = 0;
/**
* Returns boost::none if the filtering metadata for the collection is not known yet. Otherwise
* returns the most recently refreshed from the config server metadata or shard version.
*
* These methods do not check for the shard version that the operation requires and should only
* be used for cases such as checking whether a particular config server update has taken
* effect.
*/
virtual boost::optional<ScopedCollectionMetadata> getCurrentMetadataIfKnown() = 0;
virtual boost::optional<ChunkVersion> getCurrentShardVersionIfKnown() = 0;
/**
* Checks whether the shard version in the operation context is compatible with the shard
* version of the collection and if not, throws StaleConfigException populated with the received
* and wanted versions.
*/
virtual void checkShardVersionOrThrow(OperationContext* opCtx, bool isCollection) = 0;
/**
* Similar to checkShardVersionOrThrow but returns a status instead of throwing.
*/
virtual Status checkShardVersionNoThrow(OperationContext* opCtx,
bool isCollection) noexcept = 0;
/**
* Methods to control the collection's critical section. Methods listed below must be called
* with both the collection lock and CSRLock held in exclusive mode.
*
* In these methods, the CSRLock ensures concurrent access to the
* critical section.
*/
virtual void enterCriticalSectionCatchUpPhase(OperationContext* opCtx) = 0;
virtual void enterCriticalSectionCommitPhase(OperationContext* opCtx) = 0;
/**
* Method to control the collection's critical secion. Method listed below must be called with
* the collection lock in IX mode and the CSRLock in exclusive mode.
*
* In this method, the CSRLock ensures concurrent access to the
* critical section.
*/
virtual void exitCriticalSection(OperationContext* opCtx) = 0;
/**
* If the collection is currently in a critical section, returns the critical section signal to
* be waited on. Otherwise, returns nullptr.
*/
virtual std::shared_ptr<Notification<void>> getCriticalSectionSignal(
ShardingMigrationCriticalSection::Operation op) const = 0;
/**
* BSON output of the pending metadata into a BSONArray
* used for reporting/diagnostic purposes only
*/
virtual void toBSONPending(BSONArrayBuilder& bb) const = 0;
/**
* Updates the collection's filtering metadata based on changes received from the config server
* and also resolves the pending receives map in case some of these pending receives have
* committed on the config server or have been abandoned by the donor shard.
*
* This method must be called with an exclusive collection lock and it does not acquire any
* locks itself.
*/
virtual void setFilteringMetadata(OperationContext* opCtx, CollectionMetadata newMetadata) = 0;
};
/**
* Singleton factory to instantiate CollectionShardingState objects specific to the type of instance
* which is running.
*/
class CollectionShardingStateFactory {
CollectionShardingStateFactory(const CollectionShardingStateFactory&) = delete;
CollectionShardingStateFactory& operator=(const CollectionShardingStateFactory&) = delete;
public:
static void set(ServiceContext* service,
std::unique_ptr<CollectionShardingStateFactory> factory);
static void clear(ServiceContext* service);
virtual ~CollectionShardingStateFactory() = default;
/**
* Must be called prior to destruction to wait for any ongoing work to complete.
*/
virtual void join() = 0;
/**
* Called by the CollectionShardingState::get method once per newly cached namespace. It is
* invoked under a mutex and must not acquire any locks or do blocking work.
*
* Implementations must be thread-safe when called from multiple threads.
*/
virtual std::unique_ptr<CollectionShardingState> make(const NamespaceString& nss) = 0;
protected:
CollectionShardingStateFactory(ServiceContext* serviceContext)
: _serviceContext(serviceContext) {}
// The service context which owns this factory
ServiceContext* const _serviceContext;
};
} // namespace mongo
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