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/**
* Copyright (C) 2021-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 <memory>
#include "mongo/db/process_health/fault.h"
#include "mongo/db/process_health/fault_facet.h"
#include "mongo/db/process_health/fault_facet_container.h"
#include "mongo/db/process_health/fault_manager_config.h"
#include "mongo/db/process_health/health_observer.h"
#include "mongo/db/service_context.h"
#include "mongo/executor/task_executor.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/platform/mutex.h"
namespace mongo {
namespace process_health {
/**
* FaultManager is a singleton constantly monitoring the health of the
* system.
*
* It supports pluggable 'HealthObservers', which are responsible to check various
* aspects of the server health. The aggregate outcome of all periodic checks
* is accesible as FaultState.
*
* If an active fault state persists, FaultManager will terminate the server process.
*/
class FaultManager : protected FaultFacetsContainerFactory {
FaultManager(const FaultManager&) = delete;
FaultManager& operator=(const FaultManager&) = delete;
public:
// The taskExecutor provided should not be already started.
explicit FaultManager(ServiceContext* svcCtx,
std::shared_ptr<executor::TaskExecutor> taskExecutor,
std::unique_ptr<FaultManagerConfig> config);
virtual ~FaultManager();
// Start periodic health checks, invoke it once during server startup.
// It is unsafe to start health checks immediately during ServiceContext creation
// because some ServiceContext fields might not be initialized yet.
// Health checks cannot be stopped but could be effectively disabled with health-checker
// specific flags.
void startPeriodicHealthChecks();
static FaultManager* get(ServiceContext* svcCtx);
// Replace the FaultManager for the 'svcCtx'. This functionality
// is exposed for testing and initial bootstrap.
static void set(ServiceContext* svcCtx, std::unique_ptr<FaultManager> newFaultManager);
// Returns the current fault state for the server.
FaultState getFaultState() const;
// Returns the current fault, if any. Otherwise returns an empty pointer.
FaultConstPtr currentFault() const;
protected:
// Starts the health check sequence and updates the internal state on completion.
// This is invoked by the internal timer.
virtual void healthCheck();
// All observers remain valid for the manager lifetime, thus returning
// just pointers is safe, as long as they are used while manager exists.
std::vector<HealthObserver*> getHealthObservers();
// Protected interface FaultFacetsContainerFactory implementation.
// The interface FaultFacetsContainerFactory is implemented by the member '_fault'.
FaultFacetsContainerPtr getFaultFacetsContainer() const override;
FaultFacetsContainerPtr getOrCreateFaultFacetsContainer() override;
void updateWithCheckStatus(HealthCheckStatus&& checkStatus) override;
// State machine related.
void checkForStateTransition(); // Invoked by periodic thread.
// Methods that represent particular events that trigger state transition.
void processFaultExistsEvent();
void processFaultIsResolvedEvent();
// Makes a valid state transition or returns an error.
// State transition should be triggered by events above.
void transitionToState(FaultState newState);
void schedulePeriodicHealthCheckThread(bool immediately = false);
// TODO: move this into fault class; refactor to remove FaultInternal
bool hasCriticalFacet(const FaultInternal* fault) const;
std::unique_ptr<FaultManagerConfig> _config;
private:
// One time init.
void _initHealthObserversIfNeeded();
ServiceContext* const _svcCtx;
mutable Mutex _mutex =
MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(5), "FaultManager::_mutex");
std::shared_ptr<FaultInternal> _fault;
// We lazily init all health observers.
AtomicWord<bool> _initializedAllHealthObservers{false};
// Manager owns all observer instances.
std::vector<std::unique_ptr<HealthObserver>> _observers;
std::shared_ptr<executor::TaskExecutor> _taskExecutor;
boost::optional<executor::TaskExecutor::CallbackHandle> _periodicHealthCheckCbHandle;
SharedPromise<void> _initialHealthCheckCompletedPromise;
// Protects the state below.
mutable Mutex _stateMutex =
MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(0), "FaultManager::_stateMutex");
FaultState _currentState = FaultState::kStartupCheck;
// Responsible for transitioning the state of FaultManager to ActiveFault after a
// timeout while in the TransientFault state. The timer is canceled when the instance is
// destroyed.
struct TransientFaultDeadline {
TransientFaultDeadline() = delete;
TransientFaultDeadline(FaultManager* faultManager,
std::shared_ptr<executor::TaskExecutor> executor,
Milliseconds timeout);
virtual ~TransientFaultDeadline();
protected:
// Cancel timer for transitioning to ActiveFault
CancellationSource cancelActiveFaultTransition;
// Fufilled when we should transition to ActiveFault
ExecutorFuture<void> activeFaultTransition;
};
std::unique_ptr<TransientFaultDeadline> _transientFaultDeadline;
};
} // namespace process_health
} // namespace mongo
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