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/**
* Copyright (C) 2023-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/baton.h"
#include "mongo/executor/task_executor.h"
#include "mongo/util/cancellation.h"
#include "mongo/util/duration.h"
#include "mongo/util/future.h"
#include "mongo/util/interruptible.h"
#include "mongo/util/out_of_line_executor.h"
#include "mongo/util/producer_consumer_queue.h"
namespace mongo::executor {
/**
* An RAII type to run tasks inline. Multiple threads may schedule tasks on this executor, but only
* one thread can run the scheduled tasks. This executor does not own any execution resources (e.g.,
* threads), so the user must call its `run` method to process scheduled tasks.
*
* The executor is marked non-copyable to make sure there's only one runner/consumer. At
* destruction, it drains all scheduled tasks with a non-okay status and rejects new work.
*
* This is an alternative to `Baton` when an `OperationContext` is not available or a custom
* predicate should be used to interrupt running scheduled tasks. More details and examples on using
* `Batons` is available here: https://github.com/mongodb/mongo/blob/master/docs/baton.md.
*/
class InlineExecutor {
public:
/**
* Maintains the shared state between producers and the consumer.
*/
struct State {
MultiProducerSingleConsumerQueue<OutOfLineExecutor::Task> tasks;
};
InlineExecutor();
~InlineExecutor();
InlineExecutor(const InlineExecutor&) = delete;
/*
* Returns an executor that can schedule tasks on this `InlineExecutor`. This executor may
* (safely) outlive its corresponding `InlineExecutor`, but will run tasks with
* `ErrorCodes::ShutdownInProgress` once the destructor for `InlineExecutor` runs.
* This method may be called by multiple threads. The returned `OutOfLineExecutor` may also be
* safely accessed by multipe threads to schedule jobs concurrently.
*/
std::shared_ptr<OutOfLineExecutor> getExecutor() {
return _executor;
}
/*
* Blocking call that runs scheduled tasks inline until the `predicate` returns `true`.
* May throw if interrupted, or if a scheduled task throws.
* May only be called from the thread that owns this `InlineExecutor`.
*/
using Predicate = std::function<bool()>;
void run(Predicate predicate, Interruptible* interruptible = Interruptible::notInterruptible());
/*
* A wrapper to make this executor compatible with our `AsyncTry` APIs.
*/
class SleepableExecutor : public OutOfLineExecutor {
public:
void schedule(OutOfLineExecutor::Task) override = 0;
virtual ExecutorFuture<void> sleepFor(Milliseconds, const CancellationToken&) = 0;
};
/*
* Makes a `SleepableExecutor` that may schedule tasks on this `InlineExecutor`, or utilize the
* provided `baton` (if possible) or `executor` for delayed scheduling. Either `executor` or
* `baton` must contain a non-null value, but `baton` is preferred when both provided.
*/
std::shared_ptr<SleepableExecutor> getSleepableExecutor(
const std::shared_ptr<TaskExecutor>& executor,
const std::shared_ptr<Baton>& baton = nullptr);
private:
std::shared_ptr<State> _state;
std::shared_ptr<OutOfLineExecutor> _executor;
};
} // namespace mongo::executor
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