Function TestFinishNotSticky

cpp/src/arrow/util/task_group_test.cc:291–328

}

void TestFinishNotSticky(std::function<std::shared_ptr<TaskGroup>()> factory) {
  // If a task is added that runs very quickly it might decrement the task counter back
  // down to 0 and mark the completion future as complete before all tasks are added.
  // The "finished future" of the task group could get stuck to complete.
  //
  // Instead the task group should not allow the finished future to be marked complete
  // until after FinishAsync has been called.
  const int NTASKS = 100;
  for (int i = 0; i < NTASKS; ++i) {
    auto task_group = factory();
    // Add a task and let it complete
    task_group->Append([] { return Status::OK(); });
    // Wait a little bit, if the task group was going to lock the finish hopefully it
    // would do so here while we wait
    SleepFor(1e-2);

    // Add a new task that will still be running
    std::atomic<bool> ready(false);
    std::mutex m;
    std::condition_variable cv;
    task_group->Append([&m, &cv, &ready] {
      std::unique_lock<std::mutex> lk(m);
      cv.wait(lk, [&ready] { return ready.load(); });
      return Status::OK();
    });

    // Ensure task group not finished already
    auto finished = task_group->FinishAsync();
    ASSERT_FALSE(finished.is_finished());

    std::unique_lock<std::mutex> lk(m);
    ready = true;
    lk.unlock();
    cv.notify_one();

    ASSERT_FINISHES_OK(finished);
  }
}

void TestFinishNeverStarted(std::shared_ptr<TaskGroup> task_group) {
  // If we call FinishAsync we are done adding tasks so if we never added any it should be