kun yu 77e1ddd81b branch-0.4.0
Former-commit-id: a4df63653202df32d0b983de27f5c969905d17ac
2019-07-30 10:23:34 +08:00

92 lines
3.1 KiB
C++

// 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_UTIL_TASK_GROUP_H
#define ARROW_UTIL_TASK_GROUP_H
#include <functional>
#include <memory>
#include <utility>
#include "arrow/status.h"
#include "arrow/util/macros.h"
#include "arrow/util/visibility.h"
namespace arrow {
namespace internal {
class ThreadPool;
// TODO Simplify this. Subgroups don't seem necessary.
/// \brief A group of related tasks
///
/// A TaskGroup executes tasks with the signature `Status()`.
/// Execution can be serial or parallel, depending on the TaskGroup
/// implementation. When Finish() returns, it is guaranteed that all
/// tasks have finished, or at least one has errored.
///
class ARROW_EXPORT TaskGroup {
public:
/// Add a Status-returning function to execute. Execution order is
/// undefined. The function may be executed immediately or later.
template <typename Function>
void Append(Function&& func) {
return AppendReal(std::forward<Function>(func));
}
/// Wait for execution of all tasks (and subgroups) to be finished,
/// or for at least one task (or subgroup) to error out.
/// The returned Status propagates the error status of the first failing
/// task (or subgroup).
virtual Status Finish() = 0;
/// The current agregate error Status. Non-blocking, useful for stopping early.
virtual Status current_status() = 0;
/// Whether some tasks have already failed. Non-blocking , useful for stopping early.
virtual bool ok() = 0;
/// How many tasks can typically be executed in parallel.
/// This is only a hint, useful for testing or debugging.
virtual int parallelism() = 0;
/// Create a subgroup of this group. This group can only finish
/// when all subgroups have finished (this means you must be
/// be careful to call Finish() on subgroups before calling it
/// on the main group).
// XXX if a subgroup errors out, should it propagate immediately to the parent
// and to children?
virtual std::shared_ptr<TaskGroup> MakeSubGroup() = 0;
static std::shared_ptr<TaskGroup> MakeSerial();
static std::shared_ptr<TaskGroup> MakeThreaded(internal::ThreadPool*);
virtual ~TaskGroup() = default;
protected:
TaskGroup() = default;
ARROW_DISALLOW_COPY_AND_ASSIGN(TaskGroup);
virtual void AppendReal(std::function<Status()> task) = 0;
};
} // namespace internal
} // namespace arrow
#endif // ARROW_UTIL_TASK_GROUP_H