pnowojski commented on a change in pull request #18475:
URL: https://github.com/apache/flink/pull/18475#discussion_r794416248
##########
File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/io/StreamMultipleInputProcessor.java
##########
@@ -157,4 +186,66 @@ private void fullCheckAndSetAvailable() {
}
}
}
+
+ /** Visible for testing only. Do not use out side
StreamMultipleInputProcessor. */
+ @VisibleForTesting
+ public static class MultipleInputAvailabilityHelper {
+ private final CompletableFuture<?>[] cachedAvailableFutures;
+ private final Consumer[] onCompletion;
+ private CompletableFuture<?> availableFuture;
+
+ public CompletableFuture<?> getAvailableFuture() {
+ return availableFuture;
+ }
+
+ public static MultipleInputAvailabilityHelper newInstance(int
inputSize) {
+ MultipleInputAvailabilityHelper obj = new
MultipleInputAvailabilityHelper(inputSize);
+ return obj;
+ }
+
+ private MultipleInputAvailabilityHelper(int inputSize) {
+ this.cachedAvailableFutures = new CompletableFuture[inputSize];
+ this.onCompletion = new Consumer[inputSize];
+ }
+
+ @VisibleForTesting
+ public void init() {
+ for (int i = 0; i < cachedAvailableFutures.length; i++) {
+ final int inputIdx = i;
+ onCompletion[i] = (Void) -> notifyCompletion(inputIdx);
+ }
+ }
+
+ public boolean isInvalid() {
+ return availableFuture == null || availableFuture.isDone();
+ }
+
+ public void resetToUnavailable() {
+ availableFuture = new CompletableFuture<>();
+ }
+
+ private void notifyCompletion(int idx) {
+ if (availableFuture != null && !availableFuture.isDone()) {
+ availableFuture.complete(null);
+ }
+ cachedAvailableFutures[idx] = AVAILABLE;
+ }
Review comment:
> The AtomicReference without CAS operations is no difference with plain
field reference.
I'm afraid you are wrong in this regard. All atomic classes are wrappers
around `volatile` field + indeed some extra atomic CAS operations and such
[they provide happens before
relationship:](https://www.tutorialspoint.com/java_concurrency/concurrency_atomicreference.htm)
> That is, a set has a happens-before relationship with any subsequent get
on the same variable. The atomic compareAndSet method also has these memory
consistency features.
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