1 | // Licensed to the Apache Software Foundation (ASF) under one |
2 | // or more contributor license agreements. See the NOTICE file |
3 | // distributed with this work for additional information |
4 | // regarding copyright ownership. The ASF licenses this file |
5 | // to you under the Apache License, Version 2.0 (the |
6 | // "License"); you may not use this file except in compliance |
7 | // with the License. You may obtain a copy of the License at |
8 | // |
9 | // http://www.apache.org/licenses/LICENSE-2.0 |
10 | // |
11 | // Unless required by applicable law or agreed to in writing, |
12 | // software distributed under the License is distributed on an |
13 | // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
14 | // KIND, either express or implied. See the License for the |
15 | // specific language governing permissions and limitations |
16 | // under the License. |
17 | |
18 | #ifndef ARROW_UTIL_TASK_GROUP_H |
19 | #define ARROW_UTIL_TASK_GROUP_H |
20 | |
21 | #include <functional> |
22 | #include <memory> |
23 | #include <utility> |
24 | |
25 | #include "arrow/status.h" |
26 | #include "arrow/util/macros.h" |
27 | #include "arrow/util/visibility.h" |
28 | |
29 | namespace arrow { |
30 | namespace internal { |
31 | |
32 | class ThreadPool; |
33 | |
34 | // TODO Simplify this. Subgroups don't seem necessary. |
35 | |
36 | /// \brief A group of related tasks |
37 | /// |
38 | /// A TaskGroup executes tasks with the signature `Status()`. |
39 | /// Execution can be serial or parallel, depending on the TaskGroup |
40 | /// implementation. When Finish() returns, it is guaranteed that all |
41 | /// tasks have finished, or at least one has errored. |
42 | /// |
43 | class ARROW_EXPORT TaskGroup { |
44 | public: |
45 | /// Add a Status-returning function to execute. Execution order is |
46 | /// undefined. The function may be executed immediately or later. |
47 | template <typename Function> |
48 | void Append(Function&& func) { |
49 | return AppendReal(std::forward<Function>(func)); |
50 | } |
51 | |
52 | /// Wait for execution of all tasks (and subgroups) to be finished, |
53 | /// or for at least one task (or subgroup) to error out. |
54 | /// The returned Status propagates the error status of the first failing |
55 | /// task (or subgroup). |
56 | virtual Status Finish() = 0; |
57 | |
58 | /// The current agregate error Status. Non-blocking, useful for stopping early. |
59 | virtual Status current_status() = 0; |
60 | |
61 | /// Whether some tasks have already failed. Non-blocking , useful for stopping early. |
62 | virtual bool ok() = 0; |
63 | |
64 | /// How many tasks can typically be executed in parallel. |
65 | /// This is only a hint, useful for testing or debugging. |
66 | virtual int parallelism() = 0; |
67 | |
68 | /// Create a subgroup of this group. This group can only finish |
69 | /// when all subgroups have finished (this means you must be |
70 | /// be careful to call Finish() on subgroups before calling it |
71 | /// on the main group). |
72 | // XXX if a subgroup errors out, should it propagate immediately to the parent |
73 | // and to children? |
74 | virtual std::shared_ptr<TaskGroup> MakeSubGroup() = 0; |
75 | |
76 | static std::shared_ptr<TaskGroup> MakeSerial(); |
77 | static std::shared_ptr<TaskGroup> MakeThreaded(internal::ThreadPool*); |
78 | |
79 | virtual ~TaskGroup() = default; |
80 | |
81 | protected: |
82 | TaskGroup() = default; |
83 | ARROW_DISALLOW_COPY_AND_ASSIGN(TaskGroup); |
84 | |
85 | virtual void AppendReal(std::function<Status()> task) = 0; |
86 | }; |
87 | |
88 | } // namespace internal |
89 | } // namespace arrow |
90 | |
91 | #endif // ARROW_UTIL_TASK_GROUP_H |
92 | |