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/**
* Copyright (C) 2018 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 "mongo/db/pipeline/document_source.h"
#include "mongo/executor/task_executor.h"
#include "mongo/s/query/document_source_merge_cursors.h"
#include "mongo/s/shard_id.h"
namespace mongo {
/**
* An internal stage used as part of the change streams infrastructure to listen for an event
* signaling that a new shard now has potentially matching data. For example, this stage will
* detect if a collection is being watched and a chunk for that collection migrates to a shard for
* the first time. When this event is detected, this stage will establish a new cursor on that
* shard and add it to the cursors being merged.
*/
class DocumentSourceUpdateOnAddShard final : public DocumentSource {
public:
/**
* Creates a new stage which will establish a new cursor and add it to the cursors being merged
* by 'mergeCursorsStage' whenever a new shard is detected by a change stream.
*/
static boost::intrusive_ptr<DocumentSourceUpdateOnAddShard> create(
const boost::intrusive_ptr<ExpressionContext>&,
executor::TaskExecutor*,
const boost::intrusive_ptr<DocumentSourceMergeCursors>&,
std::vector<ShardId> shardsWithCursors,
BSONObj cmdToRunOnNewShards);
Value serialize(boost::optional<ExplainOptions::Verbosity> explain) const final {
// We only ever expect to add this stage if the pipeline is being executed locally on a
// mongos. In this case, it should never be serialized.
MONGO_UNREACHABLE;
}
virtual StageConstraints constraints(Pipeline::SplitState) const {
return {StreamType::kStreaming,
PositionRequirement::kNone,
HostTypeRequirement::kMongoS,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kNotAllowed,
TransactionRequirement::kNotAllowed,
ChangeStreamRequirement::kChangeStreamStage};
}
GetNextResult getNext() final;
private:
DocumentSourceUpdateOnAddShard(const boost::intrusive_ptr<ExpressionContext>&,
executor::TaskExecutor*,
const boost::intrusive_ptr<DocumentSourceMergeCursors>&,
std::vector<ShardId>&& shardsWithCursors,
BSONObj cmdToRunOnNewShards);
/**
* Establish the new cursors and tell the RouterStageMerge about them.
*/
void addNewShardCursors(const Document& newShardDetectedObj);
/**
* Open the cursors on the new shards.
*/
std::vector<RemoteCursor> establishShardCursorsOnNewShards(const Document& newShardDetectedObj);
executor::TaskExecutor* _executor;
boost::intrusive_ptr<DocumentSourceMergeCursors> _mergeCursors;
std::vector<ShardId> _shardsWithCursors;
BSONObj _cmdToRunOnNewShards;
};
} // namespace mongo
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