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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 <deque>
#include <vector>
#include "mongo/bson/ordering.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/exchange_spec_gen.h"
#include "mongo/db/pipeline/field_path.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
class Exchange : public RefCountable {
static constexpr size_t kInvalidThreadId{std::numeric_limits<size_t>::max()};
static constexpr size_t kMaxBufferSize = 100 * 1024 * 1024; // 100 MB
static constexpr size_t kMaxNumberConsumers = 100;
/**
* Convert the BSON representation of boundaries (as deserialized off the wire) to the internal
* format (KeyString).
*/
static std::vector<std::string> extractBoundaries(
const boost::optional<std::vector<BSONObj>>& obj, Ordering ordering);
/**
* Validate consumer ids coming off the wire. If the ids pass the validation then return them.
* If the ids are not provided (boost::none) then generate a sequence [0..nConsumer-1].
*/
static std::vector<size_t> extractConsumerIds(
const boost::optional<std::vector<std::int32_t>>& consumerIds, size_t nConsumers);
/**
* Extract the order description from the key.
*/
static Ordering extractOrdering(const BSONObj& keyPattern);
/**
* Extract dotted paths from the key.
*/
static std::vector<FieldPath> extractKeyPaths(const BSONObj& keyPattern);
public:
Exchange(ExchangeSpec spec, std::unique_ptr<Pipeline, PipelineDeleter> pipeline);
DocumentSource::GetNextResult getNext(OperationContext* opCtx, size_t consumerId);
size_t getConsumers() const {
return _consumers.size();
}
auto& getSpec() const {
return _spec;
}
void dispose(OperationContext* opCtx, size_t consumerId);
private:
size_t loadNextBatch();
size_t getTargetConsumer(const Document& input);
class ExchangeBuffer {
public:
bool appendDocument(DocumentSource::GetNextResult input, size_t limit);
DocumentSource::GetNextResult getNext();
bool isEmpty() const {
return _buffer.empty();
}
private:
size_t _bytesInBuffer{0};
std::deque<DocumentSource::GetNextResult> _buffer;
};
// Keep a copy of the spec for serialization purposes.
const ExchangeSpec _spec;
// A pattern for extracting a key from a document used by range and hash policies.
const BSONObj _keyPattern;
const Ordering _ordering;
const std::vector<FieldPath> _keyPaths;
// Range boundaries. The boundaries are ordered and must cover the whole domain, e.g.
// [Min, -200, 0, 200, Max] partitions the domain into 4 ranges (i.e. 1 less than number of
// boundaries). Every range has an assigned consumer that will process documents in that range.
const std::vector<std::string> _boundaries;
// A mapping from the range to consumer id. For the ranges from the example above the array must
// have 4 elements (1 for every range):
// [0, 1, 0, 1]
// consumer 0 processes ranges 1 and 3 (i.e. [Min,-200] and [0,200])
// consumer 1 processes ranges 2 and 4 (i.e. [-200,0] and [200,Max])
const std::vector<size_t> _consumerIds;
// A policy that tells how to distribute input documents to consumers.
const ExchangePolicyEnum _policy;
// If set to true then a producer sends special 'high watermark' documents to consumers in order
// to prevent deadlocks.
const bool _orderPreserving;
// A maximum size of buffer per consumer.
const size_t _maxBufferSize;
// An input to the exchange operator
std::unique_ptr<Pipeline, PipelineDeleter> _pipeline;
// Synchronization.
stdx::mutex _mutex;
stdx::condition_variable _haveBufferSpace;
// A thread that is currently loading the exchange buffers.
size_t _loadingThreadId{kInvalidThreadId};
// A status indicating that the exception was thrown during loadNextBatch(). Once in the failed
// state all other producing threads will fail too.
Status _errorInLoadNextBatch{Status::OK()};
size_t _roundRobinCounter{0};
// A rundown counter of consumers disposing of the pipelines. Only the last consumer will
// dispose of the 'inner' exchange pipeline.
size_t _disposeRunDown{0};
std::vector<std::unique_ptr<ExchangeBuffer>> _consumers;
};
class DocumentSourceExchange final : public DocumentSource {
public:
DocumentSourceExchange(const boost::intrusive_ptr<ExpressionContext>& expCtx,
const boost::intrusive_ptr<Exchange> exchange,
size_t consumerId);
GetNextResult getNext() final;
StageConstraints constraints(Pipeline::SplitState pipeState) const final {
return {StreamType::kStreaming,
PositionRequirement::kNone,
HostTypeRequirement::kNone,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kAllowed,
TransactionRequirement::kAllowed};
}
const char* getSourceName() const final;
Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
/**
* DocumentSourceExchange does not have a direct source (it is reading through the shared
* Exchange pipeline).
*/
void setSource(DocumentSource* source) final {
invariant(!source);
}
GetNextResult getNext(size_t consumerId);
size_t getConsumers() const {
return _exchange->getConsumers();
}
auto getExchange() const {
return _exchange;
}
void doDispose() final {
_exchange->dispose(pExpCtx->opCtx, _consumerId);
}
auto getConsumerId() const {
return _consumerId;
}
private:
boost::intrusive_ptr<Exchange> _exchange;
const size_t _consumerId;
};
} // namespace mongo
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