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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 <boost/optional.hpp>
#include "mongo/bson/timestamp.h"
#include "mongo/db/commands/tenant_migration_donor_cmds_gen.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/repl/optime.h"
#include "mongo/executor/task_executor.h"
#include "tenant_migration_access_blocker.h"
namespace mongo {
/**
* The TenantMigrationRecipientAccessBlocker is used to reject tenant reads at a point-in-time
* before a recipient node reaches the consistent state after a tenant migration.
*
* When data cloning is finished (and therefore a consistent donor optime established) an opObserver
* that is observing the recipient state document will create a
* TenantMigrationRecipientAccessBlocker in state `kReject` that will reject all reads (with
* SnapshotTooOld) for that tenant.
*
* When oplog application reaches this consistent point, the recipient primary will wait for
* the earlier state document write to be committed on all recipient nodes before doing the state
* machine write for the consistent state. The TenantMigrationRecipientAccessBlocker, upon see the
* write for the consistent state, will transition to `kRejectBefore` state with the
* `rejectBeforeTimestamp` set to the recipient consistent timestamp and will start allowing reads
* for read concerns which read the latest snapshot, and "atClusterTime" or "majority" read concerns
* which are after the `rejectBeforeTimestamp`. Reads for older snapshots, except "majority" until
* the majority snapshot for a node reaches the `rejectBeforeTimestamp`, will be rejected with
* SnapshotTooOld. Reads for "majority" when the majority snapshot is before the
* `rejectBeforeTimestamp` will be blocked until the majority committed snapshot reaches that
* timestamp.
*
* To ensure atClusterTime and afterClusterTime reads are consistent, when the recipient receives a
* recipientSyncData command with a returnAfterReachingTimestamp after the consistent point, the
* `rejectBeforeTimestamp` will be advanced to the given returnAfterReachingTimestamp.
*
* Blocker excludes all operations with 'tenantMigrationRecipientInfo' decoration set, as they are
* internal.
*/
class TenantMigrationRecipientAccessBlocker
: public std::enable_shared_from_this<TenantMigrationRecipientAccessBlocker>,
public TenantMigrationAccessBlocker {
public:
TenantMigrationRecipientAccessBlocker(ServiceContext* serviceContext,
UUID migrationId,
std::string tenantId,
MigrationProtocolEnum protocol,
std::string donorConnString);
//
// Called by all writes and reads against the database.
//
Status checkIfCanWrite(Timestamp writeTs) final;
Status waitUntilCommittedOrAborted(OperationContext* opCtx) final;
Status checkIfLinearizableReadWasAllowed(OperationContext* opCtx) final;
SharedSemiFuture<void> getCanReadFuture(OperationContext* opCtx, StringData command) final;
//
// Called by index build user threads before acquiring an index build slot, and again right
// after registering the build.
//
Status checkIfCanBuildIndex() final;
// @return true if TTL is blocked
bool checkIfShouldBlockTTL() const final;
// Clear TTL blocker once the state doc is garbage collectable.
void stopBlockingTTL();
/**
* Called when an optime is majority committed.
*/
void onMajorityCommitPointUpdate(repl::OpTime opTime) final;
void appendInfoForServerStatus(BSONObjBuilder* builder) const final;
UUID getMigrationId() const;
BSONObj getDebugInfo() const final;
void recordTenantMigrationError(Status status) final{};
//
// Called as a recipient to reject reads before the `timestamp`.
//
void startRejectingReadsBefore(const Timestamp& timestamp);
bool inStateReject() const {
return _state.isReject();
}
private:
/**
* The access states of an mtab.
*/
class BlockerState {
public:
void transitionToRejectBefore() {
_state = State::kRejectBefore;
}
bool isReject() const {
return _state == State::kReject;
}
bool isRejectBefore() const {
return _state == State::kRejectBefore;
}
std::string toString() const;
private:
enum class State { kReject, kRejectBefore };
State _state = State::kReject;
};
ServiceContext* _serviceContext;
const UUID _migrationId;
const std::string _tenantId;
const MigrationProtocolEnum _protocol;
const std::string _donorConnString;
// Protects the state below.
mutable Mutex _mutex = MONGO_MAKE_LATCH("TenantMigrationRecipientAccessBlocker::_mutex");
BlockerState _state;
boost::optional<Timestamp> _rejectBeforeTimestamp;
// Start with blocked TTL, unblock when the migration document is marked as
// garbage collectable.
bool _ttlIsBlocked = true;
};
} // namespace mongo
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