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/**
* Copyright (C) 2022-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/base/string_data.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/query/stats/collection_statistics.h"
#include "mongo/db/query/stats/stats_cache_loader.h"
#include "mongo/util/concurrency/thread_pool.h"
#include "mongo/util/read_through_cache.h"
namespace mongo::stats {
using StatsCacheType = ReadThroughCache<StatsPathString, StatsCacheVal>;
using StatsCacheValueHandle = StatsCacheType::ValueHandle;
/**
* Collectoin statistics read through cache. It reads from the persitent storage but never wrties to
* it.
*/
class StatsCache : public StatsCacheType {
public:
/**
* The constructor provides the Service context under which this cache has been instantiated,
* and a Thread pool to be used for invoking the blocking 'lookup' calls. The size is the number
* of entries the underlying LRU cache will hold.
*/
StatsCache(ServiceContext* service,
std::unique_ptr<StatsCacheLoader> cacheLoader,
ThreadPoolInterface& threadPool,
int size);
/**
* Returns statsCacheLoader currently used for testing only.
*/
StatsCacheLoader* getStatsCacheLoader() {
invariant(_statsCacheLoader);
return _statsCacheLoader.get();
}
private:
/**
* Reads collection stats from the underlying storage if its not found in the in memory cache.
*/
LookupResult _lookupStats(OperationContext* opCtx,
const StatsPathString& statsPath,
const ValueHandle& stats);
Mutex _mutex = MONGO_MAKE_LATCH("StatsCache::_mutex");
std::unique_ptr<StatsCacheLoader> _statsCacheLoader;
};
} // namespace mongo::stats
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