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/**
* Copyright (C) 2021-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/pipeline/document_source.h"
#include "mongo/db/pipeline/document_source_change_stream.h"
namespace mongo {
/**
* This stage detects change stream topology changes in the form of 'kNewShardDetectedOpType' events
* and forwards them directly to the executor via an exception. Using an exception bypasses the rest
* of the pipeline, ensuring that the event cannot be filtered out or modified by user-specified
* stages and that it will ultimately be available to the mongoS.
*
* The mongoS must see all 'kNewShardDetectedOpType' events, so that it knows when it needs to open
* cursors on newly active shards. These events are generated when a chunk is migrated to a shard
* that previously may not have held any data for the collection being watched, and they contain the
* information necessary for the mongoS to include the new shard in the merged change stream.
*/
class DocumentSourceChangeStreamCheckTopologyChange final : public DocumentSource {
public:
static constexpr StringData kStageName = "$_internalChangeStreamCheckTopologyChange"_sd;
static boost::intrusive_ptr<DocumentSourceChangeStreamCheckTopologyChange> createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);
static boost::intrusive_ptr<DocumentSourceChangeStreamCheckTopologyChange> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx) {
return new DocumentSourceChangeStreamCheckTopologyChange(expCtx);
}
const char* getSourceName() const final {
return kStageName.rawData();
}
StageConstraints constraints(Pipeline::SplitState pipeState) const final;
boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
return boost::none;
}
Value serialize(SerializationOptions opts = SerializationOptions()) const final override;
void addVariableRefs(std::set<Variables::Id>* refs) const final {}
private:
DocumentSourceChangeStreamCheckTopologyChange(
const boost::intrusive_ptr<ExpressionContext>& expCtx)
: DocumentSource(kStageName, expCtx) {}
GetNextResult doGetNext() final;
};
} // namespace mongo
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