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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/db/concurrency/d_concurrency.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/repl/replica_set_aware_service.h"
#include "mongo/util/concurrency/thread_pool.h"
#include "mongo/util/uuid.h"
namespace mongo {
/**
* Scoped lock to synchronize with the execution of range deletions.
* The range-deleter acquires a scoped lock in IX mode while orphans are being deleted.
* Acquiring the scoped lock in MODE_X ensures that no orphan counter in `config.rangeDeletions`
* entries is going to be updated concurrently.
*/
class ScopedRangeDeleterLock {
public:
ScopedRangeDeleterLock(OperationContext* opCtx, LockMode mode)
: _resourceLock(opCtx, _mutex.getRid(), mode) {}
private:
const Lock::ResourceLock _resourceLock;
static inline const Lock::ResourceMutex _mutex{"ScopedRangeDeleterLock"};
};
/**
* The BalancerStatsRegistry is used to cache metadata on shards, such as the orphan documents
* count. The blancer (on the config sever) periodically fetches this metadata through the
* _shardsvrGetStatsForBalancing command and uses it to evaluate balancing status of collections.
*
* The BalancerStatsRegistry is active only on replicaset primary nodes, it is initialized on stepUp
* and terminated on stepDown.
*/
class BalancerStatsRegistry : public ReplicaSetAwareServiceShardSvr<BalancerStatsRegistry> {
BalancerStatsRegistry(const BalancerStatsRegistry&) = delete;
BalancerStatsRegistry& operator=(const BalancerStatsRegistry&) = delete;
public:
BalancerStatsRegistry() = default;
/**
* Obtains the service-wide instance.
*/
static BalancerStatsRegistry* get(ServiceContext* serviceContext);
static BalancerStatsRegistry* get(OperationContext* opCtx);
/**
* Non blocking initialization. Performs an asyncronous initialization of this registry.
*/
void initializeAsync(OperationContext* opCtx);
void terminate();
/**
* Update orphan document count for a specific collection.
* `delta` is the increment/decrement that will be applied to the current cached count.
*
* If the registy is not initialized this function will be a noop.
*/
void updateOrphansCount(const UUID& collectionUUID, long long delta);
void onRangeDeletionTaskInsertion(const UUID& collectionUUID, long long numOrphanDocs);
void onRangeDeletionTaskDeletion(const UUID& collectionUUID, long long numOrphanDocs);
long long getCollNumOrphanDocs(const UUID& collectionUUID) const;
/**
* Retrieves the numOrphanDocs from the balancer stats registry if initialized or runs an
* aggregation on disk if not.
*/
long long getCollNumOrphanDocsFromDiskIfNeeded(OperationContext* opCtx,
const UUID& collectionUUID) const;
private:
void onInitialDataAvailable(OperationContext* opCtx,
bool isMajorityDataAvailable) override final {}
void onStepUpBegin(OperationContext* opCtx, long long term) override final {}
void onBecomeArbiter() override final {}
void onShutdown() override final {}
void onStartup(OperationContext* opCtx) override final;
void onStepUpComplete(OperationContext* opCtx, long long term) override final;
void onStepDown() override final;
void _loadOrphansCount(OperationContext* opCtx);
bool _isInitialized() const {
return _state.load() == State::kInitialized;
}
struct CollectionStats {
// Number of orphan documents for this collection
long long numOrphanDocs;
// Number of range deletion tasks
long long numRangeDeletionTasks;
};
enum class State {
kPrimaryIdle, // The node is primary but the registry is not initialzed
kInitializing,
kInitialized,
kTerminating,
kSecondary,
};
mutable Mutex _stateMutex = MONGO_MAKE_LATCH("BalancerStatsRegistry::_stateMutex");
AtomicWord<State> _state{State::kSecondary};
ServiceContext::UniqueOperationContext _initOpCtxHolder;
mutable Mutex _mutex = MONGO_MAKE_LATCH("BalancerStatsRegistry::_mutex");
// Map containing all the currently cached collection stats
stdx::unordered_map<UUID, CollectionStats, UUID::Hash> _collStatsMap;
// Thread pool used for asyncronous initialization
std::shared_ptr<ThreadPool> _threadPool;
};
} // namespace mongo
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