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Diffstat (limited to 'src/mongo/db/cancelable_operation_context.h')
-rw-r--r-- | src/mongo/db/cancelable_operation_context.h | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/src/mongo/db/cancelable_operation_context.h b/src/mongo/db/cancelable_operation_context.h new file mode 100644 index 00000000000..ca9493a58c2 --- /dev/null +++ b/src/mongo/db/cancelable_operation_context.h @@ -0,0 +1,95 @@ +/** + * 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/service_context.h" +#include "mongo/platform/atomic_word.h" +#include "mongo/util/future.h" +#include "mongo/util/out_of_line_executor.h" + +namespace mongo { + +class CancelationToken; +class OperationContext; + +/** + * Wrapper class around an OperationContext that calls markKilled(ErrorCodes::CallbackCanceled) when + * the supplied CancelationToken is canceled. + * + * This class is useful for having an OperationContext be interrupted when a CancelationToken is + * canceled. Note that OperationContext::getCancelationToken() is instead useful for having a + * CancelationToken be canceled when an OperationContext is interrupted. The combination of the two + * enables bridging between OperationContext interruption and CancelationToken cancellation + * arbitrarily. + * + * IMPORTANT: Executors are allowed to refuse work. markKilled(ErrorCodes::CallbackCanceled) won't + * be called when the supplied CancelationToken is canceled if the task executor has already been + * shut down, for example. Use a task executor bound to the process lifetime if you must guarantee + * that the OperationContext is interrupted when the CancelationToken is canceled. + */ +class CancelableOperationContext { +public: + CancelableOperationContext(ServiceContext::UniqueOperationContext opCtx, + const CancelationToken& cancelToken, + ExecutorPtr executor); + + CancelableOperationContext(const CancelableOperationContext&) = delete; + CancelableOperationContext& operator=(const CancelableOperationContext&) = delete; + + CancelableOperationContext(CancelableOperationContext&&) = delete; + CancelableOperationContext& operator=(CancelableOperationContext&&) = delete; + + ~CancelableOperationContext(); + + OperationContext* get() const noexcept { + return _opCtx.get(); + } + + OperationContext* operator->() const noexcept { + return get(); + } + + OperationContext& operator*() const noexcept { + return *get(); + } + +private: + struct SharedBlock { + AtomicWord<bool> done{false}; + }; + + const std::shared_ptr<SharedBlock> _sharedBlock; + const ServiceContext::UniqueOperationContext _opCtx; + const SemiFuture<void> _markKilledFinished; +}; + +} // namespace mongo |