Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/3295#discussion_r101829019
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/concurrent/FutureUtils.java
---
@@ -88,4 +100,104 @@ public RetryException(Throwable cause) {
super(cause);
}
}
+
+ //
------------------------------------------------------------------------
+ // composing futures
+ //
------------------------------------------------------------------------
+
+ /**
+ * Creates a future that is complete once multiple other futures
completed.
+ * The ConjunctFuture fails (completes exceptionally) once one of the
Futures in the
+ * conjunction fails.
+ *
+ * <p>The ConjunctFuture gives access to how many Futures in the
conjunction have already
+ * completed successfully, via {@link
ConjunctFuture#getNumFuturesCompleted()}.
+ *
+ * @param futures The futures that make up the conjunction. No null
entries are allowed.
+ * @return The ConjunctFuture that completes once all given futures are
complete (or one fails).
+ */
+ public static ConjunctFuture combineAll(Collection<? extends Future<?>>
futures) {
+ checkNotNull(futures, "futures");
+ checkArgument(!futures.isEmpty(), "futures is empty");
+
+ final ConjunctFutureImpl conjunct = new
ConjunctFutureImpl(futures.size());
+
+ for (Future<?> future : futures) {
+ future.handle(conjunct.completionHandler);
+ }
+
+ return conjunct;
+ }
+
+ /**
+ * A future that is complete once multiple other futures completed. The
futures are not
+ * necessarily of the same type, which is why the type of this Future
is {@code Void}.
+ * The ConjunctFuture fails (completes exceptionally) once one of the
Futures in the
+ * conjunction fails.
+ *
+ * <p>The advantage of using the ConjunctFuture over chaining all the
futures (such as via
+ * {@link Future#thenCombine(Future, BiFunction)}) is that
ConjunctFuture also tracks how
+ * many of the Futures are already complete.
+ */
+ public interface ConjunctFuture extends CompletableFuture<Void> {
+
+ /**
+ * Gets the total number of Futures in the conjunction.
+ * @return The total number of Futures in the conjunction.
+ */
+ int getNumFuturesTotal();
+
+ /**
+ * Gets the number of Futures in the conjunction that are
already complete.
+ * @return The number of Futures in the conjunction that are
already complete
+ */
+ int getNumFuturesCompleted();
+ }
+
+ /**
+ * The implementation of the {@link ConjunctFuture}.
+ *
+ * <p>Implementation notice: The member fields all have package-private
access, because they are
+ * either accessed by an inner subclass or by the enclosing class.
+ */
+ private static class ConjunctFutureImpl extends
FlinkCompletableFuture<Void> implements ConjunctFuture {
--- End diff --
Yes, with set rather then add it should work. Since the list gets
initialized with an array, I would actually just use an array in the first
place.
Followup ;-)
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