Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/7385#discussion_r34755173
--- Diff: core/src/main/scala/org/apache/spark/FutureAction.scala ---
@@ -116,55 +123,27 @@ class SimpleFutureAction[T] private[spark](jobWaiter:
JobWaiter[_], resultFunc:
}
override def ready(atMost: Duration)(implicit permit: CanAwait):
SimpleFutureAction.this.type = {
- if (!atMost.isFinite()) {
- awaitResult()
- } else jobWaiter.synchronized {
- val finishTime = System.currentTimeMillis() + atMost.toMillis
- while (!isCompleted) {
- val time = System.currentTimeMillis()
- if (time >= finishTime) {
- throw new TimeoutException
- } else {
- jobWaiter.wait(finishTime - time)
- }
- }
- }
+ jobWaiter.ready(atMost)(permit)
this
}
@throws(classOf[Exception])
override def result(atMost: Duration)(implicit permit: CanAwait): T = {
- ready(atMost)(permit)
- awaitResult() match {
- case scala.util.Success(res) => res
- case scala.util.Failure(e) => throw e
- }
+ jobWaiter.result(atMost)(permit) // Throws exception if the job failed.
--- End diff --
Let's see... jobWaiter.result delegates to the job waiter's
promise.future.result.
Here, I think we have an instance of DefaultPromise, whose `result`
(https://github.com/scala/scala/blob/v2.10.4/src/library/scala/concurrent/impl/Promise.scala#L222)
is implemented in terms of `ready`
(https://github.com/scala/scala/blob/v2.10.4/src/library/scala/concurrent/impl/Promise.scala#L218),
which in turn is implemented using the internal `tryAwait` method:
https://github.com/scala/scala/blob/v2.10.4/src/library/scala/concurrent/impl/Promise.scala#L194
It looks like this is implemented by scheduling an `onComplete` callback
which updates a latch. This callback runs on `Future`'s
InternalCallbackExecutor:
https://github.com/scala/scala/blob/v2.10.4/src/library/scala/concurrent/Future.scala#L590
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