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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/s/query/async_results_merger.h"
#include "mongo/s/query/router_exec_stage.h"
namespace mongo {
/**
* Layers a simpler blocking interface on top of the AsyncResultsMerger from which this
* BlockingResultsMerger is constructed.
*/
class BlockingResultsMerger {
public:
BlockingResultsMerger(OperationContext* opCtx,
AsyncResultsMergerParams&& arm,
executor::TaskExecutor*);
/**
* Blocks until the next result is available or an error is detected.
*/
StatusWith<ClusterQueryResult> next(OperationContext*, RouterExecStage::ExecContext);
Status setAwaitDataTimeout(Milliseconds awaitDataTimeout) {
return _arm.setAwaitDataTimeout(awaitDataTimeout);
}
void reattachToOperationContext(OperationContext* opCtx) {
_arm.reattachToOperationContext(opCtx);
}
void detachFromOperationContext() {
_arm.detachFromOperationContext();
}
bool remotesExhausted() const {
return _arm.remotesExhausted();
}
std::size_t getNumRemotes() const {
return _arm.getNumRemotes();
}
void addNewShardCursors(std::vector<RemoteCursor>&& newCursors) {
_arm.addNewShardCursors(std::move(newCursors));
}
/**
* Blocks until '_arm' has been killed, which involves cleaning up any remote cursors managed
* by this results merger.
*/
void kill(OperationContext* opCtx);
private:
/**
* Awaits the next result from the ARM with no time limit.
*/
StatusWith<ClusterQueryResult> blockUntilNext(OperationContext* opCtx);
/**
* Awaits the next result from the ARM up to the time limit specified on 'opCtx'. If this is the
* user's initial find or we have already obtained at least one result for this batch, this
* method returns EOF immediately rather than blocking.
*/
StatusWith<ClusterQueryResult> awaitNextWithTimeout(OperationContext* opCtx,
RouterExecStage::ExecContext execCtx);
/**
* Returns the next event to wait upon - either a new event from the ARM, or a valid preceding
* event which we scheduled during the previous call to next().
*/
StatusWith<executor::TaskExecutor::EventHandle> getNextEvent();
TailableModeEnum _tailableMode;
executor::TaskExecutor* _executor;
// In a case where we have a tailable, awaitData cursor, a call to 'next()' will block waiting
// for an event generated by '_arm', but may time out waiting for this event to be triggered.
// While it's waiting, the time limit for the 'awaitData' piece of the cursor may have been
// exceeded. When this happens, we use '_leftoverEventFromLastTimeout' to remember the old event
// and pick back up waiting for it on the next call to 'next()'.
executor::TaskExecutor::EventHandle _leftoverEventFromLastTimeout;
AsyncResultsMerger _arm;
};
} // namespace mongo
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