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/**
* Copyright (C) 2019-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 <vector>
#include "mongo/base/status.h"
#include "mongo/platform/mutex.h"
#include "mongo/util/functional.h"
#include "mongo/util/hierarchical_acquisition.h"
namespace mongo {
/**
* Offers a type which allows idl to register observers for server parameters at runtime.
*
* An easy way to leverage this type is to register it as an on_update handler via
* on_update: std::ref(someGlobalMutableObserverRegistry)
*
* Then adding observers via someGlobalMutableObserverRegistry.addObserver();
*/
template <typename T>
class MutableObserverRegistry {
public:
using Argument = T;
void addObserver(unique_function<void(const T&)> observer) {
stdx::lock_guard lk(_mutex);
_registry.emplace_back(std::move(observer));
}
// TODO SERVER-40224: remove the Status return when on_update is changed to return void
Status operator()(const T& t) {
stdx::lock_guard lk(_mutex);
for (const auto& observer : _registry) {
observer(t);
}
return Status::OK();
}
private:
Mutex _mutex =
MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(0), "MutableObserverRegistry::_mutex");
std::vector<unique_function<void(const T&)>> _registry;
};
} // namespace mongo
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