westonpace commented on code in PR #14257:
URL: https://github.com/apache/arrow/pull/14257#discussion_r989220819
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cpp/src/arrow/util/async_util.cc:
##########
@@ -98,13 +98,53 @@ class FifoQueue : public AsyncTaskScheduler::Queue {
std::list<std::unique_ptr<Task>> tasks_;
};
+class AlreadyFailedScheduler : public AsyncTaskScheduler {
+ public:
+ explicit AlreadyFailedScheduler(Status failure_reason,
+ FnOnce<Status(Status)> finish_callback)
+ : failure_reason_(std::move(failure_reason)),
+ finish_callback_(std::move(finish_callback)) {}
+ bool AddTask(std::unique_ptr<Task> task) override { return false; }
+ void End() override {
+ std::ignore = std::move(finish_callback_)(failure_reason_);
+ self.reset();
+ }
+ Future<> OnFinished() const override {
+ DCHECK(false) << "You should not rely on sub-scheduler's OnFinished. Use
a "
+ "finished callback when creating the sub-scheduler
instead";
+ return Future<>::MakeFinished(Status::UnknownError("Unreachable code
encountered"));
+ }
+ AsyncTaskScheduler* MakeSubScheduler(FnOnce<Status(Status)> finish_callback,
+ Throttle* throttle,
+ std::unique_ptr<Queue> queue) override {
+ return AlreadyFailedScheduler::Make(failure_reason_,
std::move(finish_callback));
+ }
Review Comment:
I'm moving the finish callback passed in and not `finish_callback_` (which
is the finish callback for the parent scheduler). That being said, the very
first scheduler doesn't have a finish callback by design.
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