path: root/src/mongo/db/repl/collection_cloner.h

/**
 *    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 <memory>
#include <string>
#include <vector>

#include "mongo/base/disallow_copying.h"
#include "mongo/base/status.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/client/fetcher.h"
#include "mongo/db/catalog/collection_options.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/repl/base_cloner.h"
#include "mongo/db/repl/replication_executor.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/net/hostandport.h"

namespace mongo {
namespace repl {

class CollectionCloner : public BaseCloner {
    MONGO_DISALLOW_COPYING(CollectionCloner);

public:
    /**
     * Storage interface for collection cloner.
     *
     * Supports the operations on the storage layer required by the cloner.
     */
    class StorageInterface;

    /**
     * Type of function to schedule database work with the executor.
     *
     * Must be consistent with ReplicationExecutor::scheduleWorkWithGlobalExclusiveLock().
     *
     * Used for testing only.
     */
    using ScheduleDbWorkFn = stdx::function<StatusWith<ReplicationExecutor::CallbackHandle>(
        const ReplicationExecutor::CallbackFn&)>;

    /**
     * Creates CollectionCloner task in inactive state. Use start() to activate cloner.
     *
     * The cloner calls 'onCompletion' when the collection cloning has completed or failed.
     *
     * 'onCompletion' will be called exactly once.
     *
     * Takes ownership of the passed StorageInterface object.
     */
    CollectionCloner(ReplicationExecutor* executor,
                     const HostAndPort& source,
                     const NamespaceString& sourceNss,
                     const CollectionOptions& options,
                     const CallbackFn& onCompletion,
                     StorageInterface* storageInterface);

    virtual ~CollectionCloner();

    const NamespaceString& getSourceNamespace() const;

    std::string getDiagnosticString() const override;

    bool isActive() const override;

    Status start() override;

    void cancel() override;

    void wait() override;

    //
    // Testing only functions below.
    //

    /**
     * Waits for database worker to complete.
     * Returns immediately if collection cloner is not active.
     *
     * For testing only.
     */
    void waitForDbWorker();

    /**
     * Overrides how executor schedules database work.
     *
     * For testing only.
     */
    void setScheduleDbWorkFn(const ScheduleDbWorkFn& scheduleDbWorkFn);

private:
    /**
     * Read index specs from listIndexes result.
     */
    void _listIndexesCallback(const StatusWith<Fetcher::QueryResponse>& fetchResult,
                              Fetcher::NextAction* nextAction,
                              BSONObjBuilder* getMoreBob);

    /**
     * Read collection documents from find result.
     */
    void _findCallback(const StatusWith<Fetcher::QueryResponse>& fetchResult,
                       Fetcher::NextAction* nextAction,
                       BSONObjBuilder* getMoreBob);

    /**
     * Request storage interface to create collection.
     *
     * Called multiple times if there are more than one batch of responses from listIndexes
     * cursor.
     *
     * 'nextAction' is an in/out arg indicating the next action planned and to be taken
     *  by the fetcher.
     */
    void _beginCollectionCallback(const ReplicationExecutor::CallbackArgs& callbackData);

    /**
     * Called multiple times if there are more than one batch of documents from the fetcher.
     * On the last batch, 'lastBatch' will be true.
     *
     * Each document returned will be inserted via the storage interfaceRequest storage
     * interface.
     */
    void _insertDocumentsCallback(const ReplicationExecutor::CallbackArgs& callbackData,
                                  bool lastBatch);

    /**
     * Reports completion status.
     * Commits/aborts collection building.
     * Sets cloner to inactive.
     */
    void _finishCallback(OperationContext* txn, const Status& status);

    // Not owned by us.
    ReplicationExecutor* _executor;

    HostAndPort _source;
    NamespaceString _sourceNss;
    NamespaceString _destNss;
    CollectionOptions _options;

    // Invoked once when cloning completes or fails.
    CallbackFn _onCompletion;

    // Not owned by us.
    StorageInterface* _storageInterface;

    // Protects member data of this collection cloner.
    mutable stdx::mutex _mutex;

    mutable stdx::condition_variable _condition;

    // _active is true when Collection Cloner is started.
    bool _active;

    // Fetcher instances for running listIndexes and find commands.
    Fetcher _listIndexesFetcher;
    Fetcher _findFetcher;

    std::vector<BSONObj> _indexSpecs;

    // Current batch of documents read from fetcher to insert into collection.
    std::vector<BSONObj> _documents;

    // Callback handle for database worker.
    ReplicationExecutor::CallbackHandle _dbWorkCallbackHandle;

    // Function for scheduling database work using the executor.
    ScheduleDbWorkFn _scheduleDbWorkFn;
};

/**
 * Storage interface used by the collection cloner to build a collection.
 *
 * Operation context is provided by the replication executor via the cloner.
 *
 * The storage interface is expected to acquire locks on any resources it needs
 * to perform any of its functions.
 *
 * TODO: Consider having commit/abort/cancel functions.
 */
class CollectionCloner::StorageInterface {
public:
    virtual ~StorageInterface() = default;

    /**
     * Creates a collection with the provided indexes.
     *
     * Assume that no database locks have been acquired prior to calling this
     * function.
     */
    virtual Status beginCollection(OperationContext* txn,
                                   const NamespaceString& nss,
                                   const CollectionOptions& options,
                                   const std::vector<BSONObj>& indexSpecs) = 0;

    /**
     * Inserts documents into a collection.
     *
     * Assume that no database locks have been acquired prior to calling this
     * function.
     */
    virtual Status insertDocuments(OperationContext* txn,
                                   const NamespaceString& nss,
                                   const std::vector<BSONObj>& documents) = 0;

    /**
     * Commits changes to collection. No effect if collection building has not begun.
     * Operation context could be null.
     */
    virtual Status commitCollection(OperationContext* txn, const NamespaceString& nss) = 0;

    /**
     * Inserts missing document into a collection (not related to insertDocuments above),
     * during initial sync retry logic
     */
    virtual Status insertMissingDoc(OperationContext* txn,
                                    const NamespaceString& nss,
                                    const BSONObj& doc) = 0;

    /**
     * Inserts missing document into a collection (not related to insertDocuments above),
     * during initial sync retry logic
     */
    virtual Status dropUserDatabases(OperationContext* txn) = 0;
};

}  // namespace repl
}  // namespace mongo