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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
#pragma once
#include <functional>
#include <memory>
#include <string>
#include <vector>
#include "arrow/status.h"
#include "arrow/type_fwd.h"
#include "arrow/util/macros.h"
#include "arrow/util/visibility.h"
namespace arrow {
class StopToken;
struct StopSourceImpl;
/// EXPERIMENTAL
class ARROW_EXPORT StopSource {
public:
StopSource();
~StopSource();
// Consumer API (the side that stops)
void RequestStop();
void RequestStop(Status error);
// Async-signal-safe. TODO Deprecate this?
void RequestStopFromSignal(int signum);
StopToken token();
// For internal use only
void Reset();
protected:
std::shared_ptr<StopSourceImpl> impl_;
};
/// EXPERIMENTAL
class ARROW_EXPORT StopToken {
public:
// Public for Cython
StopToken() {}
explicit StopToken(std::shared_ptr<StopSourceImpl> impl) : impl_(std::move(impl)) {}
// A trivial token that never propagates any stop request
static StopToken Unstoppable() { return StopToken(); }
/// \brief Check if the stop source has been cancelled.
///
/// Producers should call this method, whenever convenient, to check and
/// see if they should stop producing early (i.e. have been cancelled).
/// Failure to call this method often enough will lead to an unresponsive
/// cancellation.
///
/// This is part of the producer API (the side that gets asked to stop)
/// This method is thread-safe
///
/// \return An OK status if the stop source has not been cancelled or a
/// cancel error if the source has been cancelled.
Status Poll() const;
bool IsStopRequested() const;
protected:
std::shared_ptr<StopSourceImpl> impl_;
};
/// EXPERIMENTAL: Set a global StopSource that can receive signals
///
/// The only allowed order of calls is the following:
/// - SetSignalStopSource()
/// - any number of pairs of (RegisterCancellingSignalHandler,
/// UnregisterCancellingSignalHandler) calls
/// - ResetSignalStopSource()
///
/// Beware that these settings are process-wide. Typically, only one
/// thread should call these APIs, even in a multithreaded setting.
ARROW_EXPORT
Result<StopSource*> SetSignalStopSource();
/// EXPERIMENTAL: Reset the global signal-receiving StopSource
///
/// This will invalidate the pointer returned by SetSignalStopSource.
ARROW_EXPORT
void ResetSignalStopSource();
/// EXPERIMENTAL: Register signal handler triggering the signal-receiving StopSource
///
/// Note that those handlers are automatically un-registered in a fork()ed process,
/// therefore the child process will need to call RegisterCancellingSignalHandler()
/// if desired.
ARROW_EXPORT
Status RegisterCancellingSignalHandler(const std::vector<int>& signals);
/// EXPERIMENTAL: Unregister signal handler set up by RegisterCancellingSignalHandler
ARROW_EXPORT
void UnregisterCancellingSignalHandler();
} // namespace arrow
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