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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 <map>
#include "mongo/db/index_names.h"
#include "mongo/platform/atomic_word.h"
namespace mongo {
class IndexDescriptor;
class ServiceContext;
/**
* IndexFeatures describes an anonymized set of features about a single index. For example, an index
* can be both compound and unique, and this set of flags would be used to track that information so
* that we can provide aggregated details in the AggregatedIndexUsageTracker.
*/
struct IndexFeatures {
/**
* Create an IndexFeatures structure. If 'internal' is true, the statistics for this index and
* its features should not be tracked and aggregated by the AggregatedIndexUsageTracker.
*/
static IndexFeatures make(const IndexDescriptor* desc, bool internal);
IndexType type;
bool collation = false;
bool compound = false;
bool id = false;
bool internal = false;
bool partial = false;
bool regular = false;
bool sparse = false;
bool ttl = false;
bool unique = false;
};
/**
* IndexFeatureStats holds statistics about a specific index feature. Its data members are mutable
* atomics to allow itself to be used in a const map safely.
*/
struct IndexFeatureStats {
// Number of indexes that have this feature.
mutable AtomicWord<long long> count{0};
// Number of operations that have used indexes with this feature.
mutable AtomicWord<long long> accesses{0};
};
/**
* AggregatedIndexUsageTracker aggregates usage metrics about features used by indexes. Ignores
* indexes on internal databases.
*/
class AggregatedIndexUsageTracker {
public:
static AggregatedIndexUsageTracker* get(ServiceContext* svcCtx);
AggregatedIndexUsageTracker();
/**
* Updates counters for features used by an index when the index has been accessed.
*/
void onAccess(const IndexFeatures& features) const;
/**
* Updates counters for indexes using certain features when the index has been created.
*/
void onRegister(const IndexFeatures& features) const;
/**
* Updates counters for indexes using certain features when the index has been removed.
*/
void onUnregister(const IndexFeatures& features) const;
/**
* Iterates through each feature being tracked with a call back to OnFeatureFn, which provides
* the string descriptor of the feature and its stats.
*/
using OnFeatureFn =
std::function<void(const std::string& feature, const IndexFeatureStats& stats)>;
void forEachFeature(OnFeatureFn&& onFeature) const;
/**
* Returns the total number of indexes being tracked.
*/
long long getCount() const;
private:
/**
* Internal helper to update the global stats for each index feature in 'features'. Call back
* into UpdateFn which is responsible for update the relevant statistic for each of the features
* in use.
*/
using UpdateFn = std::function<void(const IndexFeatureStats* stats)>;
void _updateStatsForEachFeature(const IndexFeatures& features, UpdateFn&& onFeature) const;
// This maps index feature description strings (e.g. 'compound', 'unique') to the actual global
// metrics counters for those features. It is intentionally ordered to have consistent
// alphabetical ordering when displayed. This map is const because we know all of its entries
// ahead of time and we can avoid the extra cost of additional concurrency control.
const std::map<std::string, IndexFeatureStats> _indexFeatureToStats;
// Total number of indexes being tracked.
mutable AtomicWord<long long> _count;
};
} // namespace mongo
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