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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/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/repl/replica_set_aware_service.h"
#include "mongo/db/service_context.h"
namespace mongo {
namespace user_writes_recoverable_critical_section_util {
bool inRecoveryMode(OperationContext* opCtx);
}
/**
* Represents the 'user writes blocking' critical section. The critical section status is persisted
* on disk and it's in-memory representation is kept in sync with the persisted state through an
* OpObserver that reacts to the inserts/updates/deletes on the persisted document.
*
* On replicaSets, enable blocking is depicted by transition (1); and disable blocking is depicted
* by transition (2):
*
* (1) acquireRecoverableCriticalSectionBlockingUserWrites()
* ---------------------------------------------------------
* | |
* | v
* + --------------------+ + --------------------+
* | User writes allowed | | User writes blocked |
* + --------------------+ + --------------------+
* ^ ^
* | |
* ---------------------------------------------------------
* (2) releaseRecoverableCriticalSection()
*
* On sharded clusters, blocking/unblocking happens as a two-phase protocol. Enable blocking is
* depicted by transitions (1) and (2); and disable blocking is depicted by (3) and (4):
*
* (2) promoteRecoverableCriticalSectionToBlockUserWrites()
* ------------------------
* | |
* (1) acquireRecoverableCriticalSectionBlockNewShardedDDL() | |
* --------------------------------- | |
* | | | |
* | V | v
* + -------------------------+ + -------------------------+ + -------------------------+
* | User writes allowed, | | User writes allowed, | | User writes blocked |
* | User sharded DDL allowed | | User sharded DDL blocked | | User sharded DDL blocked |
* + -------------------------+ + -------------------------+ + -------------------------+
* ^ ^ |
* | | | |
* -------------------------------- | |
* (4) releaseRecoverableCriticalSection() | |
* | |
* -----------------------------
* (3) demoteRecoverableCriticalSectionToNoLongerBlockUserWrites()
*
*/
class UserWritesRecoverableCriticalSectionService
: public ReplicaSetAwareService<UserWritesRecoverableCriticalSectionService> {
public:
static const NamespaceString kGlobalUserWritesNamespace;
UserWritesRecoverableCriticalSectionService() = default;
static UserWritesRecoverableCriticalSectionService* get(ServiceContext* serviceContext);
static UserWritesRecoverableCriticalSectionService* get(OperationContext* opCtx);
bool shouldRegisterReplicaSetAwareService() const override;
/**
* Acquires the user writes critical section blocking user writes. This should be used only on
* replica sets.
*/
void acquireRecoverableCriticalSectionBlockingUserWrites(OperationContext* opCtx,
const NamespaceString& nss);
/**
* Acquires the user writes critical section blocking only new sharded DDL operations, but not
* user writes nor local DDL. This is a 'prepare' state before user writes and local DDL can be
* blocked on sharded clusters.
* Note: This method does not wait for ongoing DDL coordinators to finish. If the caller wishes
* to ensure that any ongoing DDL operation has seen the new blocking state, the caller should
* wait for the ShardingDDLCoordinators to drain itself.
*/
void acquireRecoverableCriticalSectionBlockNewShardedDDL(OperationContext* opCtx,
const NamespaceString& nss);
/**
* Promotes a user writes critical section that is in the 'prepare' state (i.e. only blocking
* sharded DDL) to start blocking also user writes. This should be run only after all shards in
* the cluster have entered the 'prepare' state.
*/
void promoteRecoverableCriticalSectionToBlockUserWrites(OperationContext* opCtx,
const NamespaceString& nss);
/**
* Demotes a user writes critical section that is blocking both sharded DDL and user writes to
* only block sharded DDL. This is a preparation step before allowing user writes again on
* sharded clusters.
*/
void demoteRecoverableCriticalSectionToNoLongerBlockUserWrites(OperationContext* opCtx,
const NamespaceString& nss);
/**
* Releases the user writes critical section, allowing user writes again. On sharded clusters,
* before this method is called all shards must have first demoted their critical sections to no
* longer block user writes.
*/
void releaseRecoverableCriticalSection(OperationContext* opCtx, const NamespaceString& nss);
/**
* This method is called when we have to mirror the state on disk of the recoverable critical
* section to memory (on startUp or on rollback).
*/
void recoverRecoverableCriticalSections(OperationContext* opCtx);
private:
void onInitialDataAvailable(OperationContext* opCtx,
bool isMajorityDataAvailable) override final {
recoverRecoverableCriticalSections(opCtx);
}
void onStartup(OperationContext* opCtx) override final {}
void onSetCurrentConfig(OperationContext* opCtx) override final {}
void onShutdown() override final {}
void onStepUpBegin(OperationContext* opCtx, long long term) override final {}
void onStepUpComplete(OperationContext* opCtx, long long term) override final {}
void onStepDown() override final {}
void onBecomeArbiter() override final {}
};
} // namespace mongo
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