arrow/util/cancel.h

0001 // Licensed to the Apache Software Foundation (ASF) under one
0002 // or more contributor license agreements.  See the NOTICE file
0003 // distributed with this work for additional information
0004 // regarding copyright ownership.  The ASF licenses this file
0005 // to you under the Apache License, Version 2.0 (the
0006 // "License"); you may not use this file except in compliance
0007 // with the License.  You may obtain a copy of the License at
0008 //
0009 //   http://www.apache.org/licenses/LICENSE-2.0
0010 //
0011 // Unless required by applicable law or agreed to in writing,
0012 // software distributed under the License is distributed on an
0013 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
0014 // KIND, either express or implied.  See the License for the
0015 // specific language governing permissions and limitations
0016 // under the License.
0017
0018 #pragma once
0019
0020 #include <functional>
0021 #include <memory>
0022 #include <string>
0023 #include <vector>
0024
0025 #include "arrow/status.h"
0026 #include "arrow/type_fwd.h"
0027 #include "arrow/util/macros.h"
0028 #include "arrow/util/visibility.h"
0029
0030 namespace arrow {
0031
0032 class StopToken;
0033
0034 struct StopSourceImpl;
0035
0036 /// EXPERIMENTAL
0037 class ARROW_EXPORT StopSource {
0038  public:
0039   StopSource();
0040   ~StopSource();
0041
0042   // Consumer API (the side that stops)
0043   void RequestStop();
0044   void RequestStop(Status error);
0045   // Async-signal-safe. TODO Deprecate this?
0046   void RequestStopFromSignal(int signum);
0047
0048   StopToken token();
0049
0050   // For internal use only
0051   void Reset();
0052
0053  protected:
0054   std::shared_ptr<StopSourceImpl> impl_;
0055 };
0056
0057 /// EXPERIMENTAL
0058 class ARROW_EXPORT StopToken {
0059  public:
0060   // Public for Cython
0061   StopToken() = default;
0062
0063   explicit StopToken(std::shared_ptr<StopSourceImpl> impl) : impl_(std::move(impl)) {}
0064
0065   // A trivial token that never propagates any stop request
0066   static StopToken Unstoppable() { return StopToken(); }
0067
0068   /// \brief Check if the stop source has been cancelled.
0069   ///
0070   /// Producers should call this method, whenever convenient, to check and
0071   /// see if they should stop producing early (i.e. have been cancelled).
0072   /// Failure to call this method often enough will lead to an unresponsive
0073   /// cancellation.
0074   ///
0075   /// This is part of the producer API (the side that gets asked to stop)
0076   /// This method is thread-safe
0077   ///
0078   /// \return An OK status if the stop source has not been cancelled or a
0079   ///         cancel error if the source has been cancelled.
0080   Status Poll() const;
0081   bool IsStopRequested() const;
0082
0083  protected:
0084   std::shared_ptr<StopSourceImpl> impl_;
0085 };
0086
0087 /// EXPERIMENTAL: Set a global StopSource that can receive signals
0088 ///
0089 /// The only allowed order of calls is the following:
0090 /// - SetSignalStopSource()
0091 /// - any number of pairs of (RegisterCancellingSignalHandler,
0092 ///   UnregisterCancellingSignalHandler) calls
0093 /// - ResetSignalStopSource()
0094 ///
0095 /// Beware that these settings are process-wide.  Typically, only one
0096 /// thread should call these APIs, even in a multithreaded setting.
0097 ARROW_EXPORT
0098 Result<StopSource*> SetSignalStopSource();
0099
0100 /// EXPERIMENTAL: Reset the global signal-receiving StopSource
0101 ///
0102 /// This will invalidate the pointer returned by SetSignalStopSource.
0103 ARROW_EXPORT
0104 void ResetSignalStopSource();
0105
0106 /// EXPERIMENTAL: Register signal handler triggering the signal-receiving StopSource
0107 ///
0108 /// Note that those handlers are automatically un-registered in a fork()ed process,
0109 /// therefore the child process will need to call RegisterCancellingSignalHandler()
0110 /// if desired.
0111 ARROW_EXPORT
0112 Status RegisterCancellingSignalHandler(const std::vector<int>& signals);
0113
0114 /// EXPERIMENTAL: Unregister signal handler set up by RegisterCancellingSignalHandler
0115 ARROW_EXPORT
0116 void UnregisterCancellingSignalHandler();
0117
0118 }  // namespace arrow