[GitHub] [arrow] westonpace commented on a change in pull request #10968: ARROW-13680: [C++] Create an asynchronous nursery to simplify capture logic

[GitBox <gi...@apache.org>]

westonpace commented on a change in pull request #10968:
URL: https://github.com/apache/arrow/pull/10968#discussion_r693638540



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File path: cpp/src/arrow/util/async_nursery.h
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@@ -0,0 +1,144 @@
+// 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.
+
+#ifndef ARROW_ASYNC_NURSERY_H
+#define ARROW_ASYNC_NURSERY_H
+
+#include <list>
+
+#include "arrow/result.h"
+#include "arrow/status.h"
+#include "arrow/util/future.h"
+#include "arrow/util/mutex.h"
+
+namespace arrow {
+namespace util {
+
+class OwnedAsyncCloseable;
+
+/// An object which should be asynchronously closed before it is destroyed
+///
+/// Any AsyncCloseable must be kept alive until its parent is destroyed (this is a given
+/// if the parent is a nursery).  For shorter lived tasks/objects consider
+/// OwnedAsyncCloseable adding a dependent task.
+class AsyncCloseable {
+ public:
+  /// \brief Construct an AsyncCloseable as a child of `parent`
+  explicit AsyncCloseable(AsyncCloseable* parent);
+  virtual ~AsyncCloseable();
+
+  /// Returns a future that is completed when this object is finished closing
+  Future<> OnClosed();
+
+ protected:
+  /// Closes the AsyncCloseable
+  /// This will first call DoClose and then simultaneously close all children and
+  /// tasks_
+  virtual Future<> Close();
+  /// Subclasses should override this and perform any cleanup that is not captured by
+  /// tasks_.  Once the future returned by this method finishes then this object is
+  /// eligible for destruction and any reference to `this` may be invalid
+  virtual Future<> DoClose() = 0;
+
+  /// This method is called by subclasses to add tasks which must complete before the
+  /// object can be safely deleted
+  void AddDependentTask(Future<> task);
+  /// This method can be called by subclasses for error checking purposes.  It will
+  /// return an invalid status if this object has started closing
+  Status CheckClosed() const;
+  /// This can be used for sanity checking that a callback is not run after close has
+  /// been finished.  It will assert if the object has been fully closed (and `this`
+  /// references are unsafe)
+  void AssertNotCloseComplete() const;
+
+ private:
+  Future<> CloseChildren();
+
+  std::list<AsyncCloseable*> children_;
+  std::list<AsyncCloseable*>::iterator self_itr_;
+  std::list<std::shared_ptr<AsyncCloseable>> owned_children_;
+  std::vector<Future<>> tasks_;
+  Future<> on_closed_;
+  std::atomic<bool> closed_{false};
+  std::atomic<bool> close_complete_{false};
+  util::Mutex mutex_;
+
+  friend OwnedAsyncCloseable;
+};
+
+/// An override of AsyncCloseable which is eligible for eviction.  Instances must be

Review comment:
       I removed the concept of eviction.




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