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/**
* Copyright (C) 2020-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/operation_context.h"
#include "mongo/platform/mutex.h"
#include "mongo/rpc/topology_version_gen.h"
#include "mongo/s/mongos_hello_response.h"
#include "mongo/transport/hello_metrics.h"
#include "mongo/util/concurrency/with_lock.h"
#include <memory>
namespace mongo {
class MongosTopologyCoordinator {
public:
static MongosTopologyCoordinator* get(OperationContext* opCtx);
/**
* Constructs a Mongos Topology Coordinator object.
**/
MongosTopologyCoordinator();
/**
* Constructs and returns a MongosHelloResponse. Will block until the given deadline waiting
* for a significant topology change if the 'counter' field of 'clientTopologyVersion' is equal
* to the current TopologyVersion 'counter' maintained by this class. Returns immediately if
* 'clientTopologyVersion' < TopologyVersion of this class or if the processId
* differs.
*
* Note that Quiesce Mode is the only valid topology change on mongos.
*/
std::shared_ptr<const MongosHelloResponse> awaitHelloResponse(
OperationContext* opCtx,
boost::optional<TopologyVersion> clientTopologyVersion,
boost::optional<Date_t> deadline) const;
/**
* We only enter quiesce mode during the shutdown process, which means that the
* MongosTopologyCoordinator will never need to reset _inQuiesceMode. This function causes us
* to increment the topologyVersion and start failing hello requests with ShutdownInProgress.
* This will inform clients to route new operations to another mongos.
*
* We also sleep for quiesceTime, which allows short running operations to finish.
*/
void enterQuiesceModeAndWait(OperationContext* opCtx, Milliseconds quiesceTime);
TopologyVersion getTopologyVersion() const {
stdx::lock_guard lk(_mutex);
return _topologyVersion;
}
bool inQuiesceMode() const {
stdx::lock_guard lk(_mutex);
return _inQuiesceMode;
}
private:
using SharedPromiseOfMongosHelloResponse =
SharedPromise<std::shared_ptr<const MongosHelloResponse>>;
/**
* Calculates the time (in millis) left in quiesce mode and converts the value to int64.
*/
long long _calculateRemainingQuiesceTimeMillis() const;
/**
* Helper for constructing a MongosHelloResponse.
**/
std::shared_ptr<MongosHelloResponse> _makeHelloResponse(WithLock) const;
//
// All member variables are labeled with one of the following codes indicating the
// synchronization rules for accessing them.
//
// (M) Reads and writes guarded by _mutex
// Protects member data of this MongosTopologyCoordinator.
mutable Mutex _mutex = MONGO_MAKE_LATCH("MongosTopologyCoordinator::_mutex");
// Keeps track of the current mongos TopologyVersion.
TopologyVersion _topologyVersion; // (M)
// True if we're in quiesce mode. If true, we'll respond to hello requests with ok:0.
bool _inQuiesceMode; // (M)
// The deadline until which quiesce mode will last.
Date_t _quiesceDeadline; // (M)
// The promise waited on by awaitable hello requests on mongos.
std::shared_ptr<SharedPromiseOfMongosHelloResponse> _promise; // (M)
};
} // namespace mongo
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