Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/2760#discussion_r18854088
--- Diff: core/src/main/scala/org/apache/spark/FutureAction.scala ---
@@ -271,3 +274,55 @@ class ComplexFutureAction[T] extends FutureAction[T] {
def jobIds = jobs
}
+
+private[spark]
+class JavaFutureActionWrapper[S, T](futureAction: FutureAction[S],
converter: S => T)
+ extends JavaFutureAction[T] {
+
+ import scala.collection.JavaConverters._
+
+ override def isCancelled: Boolean = futureAction.isCancelled
+
+ override def isDone: Boolean = {
+ // According to java.util.Future's Javadoc, this returns True if the
task was completed,
+ // whether that completion was due to succesful execution, an
exception, or a cancellation.
+ futureAction.isCancelled || futureAction.isCompleted
+ }
+
+ override def jobIds(): java.util.List[java.lang.Integer] = {
+ new java.util.ArrayList(futureAction.jobIds.map(x => new
Integer(x)).asJava)
+ }
+
+ private def getImpl(timeout: Duration): T = {
+ // This will throw TimeoutException on timeout:
+ Await.ready(futureAction, timeout)
+ futureAction.value.get match {
+ case scala.util.Success(value) => converter(value)
+ case Failure(exception) =>
+ if (isCancelled) {
+ throw new CancellationException("Job cancelled:
${exception.message}");
+ } else {
+ // java.util.Future.get() wraps exceptions in ExecutionException
+ throw new ExecutionException("Exception thrown by job: ",
exception)
+ }
+ }
+ }
+
+ override def get(): T = getImpl(Duration.Inf)
+
+ override def get(timeout: Long, unit: TimeUnit): T =
+ getImpl(Duration.fromNanos(unit.toNanos(timeout)))
+
+ override def cancel(mayInterruptIfRunning: Boolean): Boolean = {
+ if (isDone) {
+ // According to java.util.Future's Javadoc, this should return false
if the task is completed.
+ false
+ } else {
+ // We're limited in terms of the semantics we can provide here; our
cancellation is
+ // asynchronous and doesn't provide a mechanism to not cancel if the
job is running.
+ futureAction.cancel()
+ true
--- End diff --
From a purely pedant point of view, it's still possible for two threads to
call `cancel()` and reach here, which means two cancelations would return
`true` and violate the contract. Not a big deal though.
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