zhijiangW commented on a change in pull request #9717: [FLINK-14044] [runtime]
Reducing synchronization in AsyncWaitOperator
URL: https://github.com/apache/flink/pull/9717#discussion_r328422187
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File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/async/queue/UnorderedStreamElementQueue.java
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@@ -19,192 +19,146 @@
package org.apache.flink.streaming.api.operators.async.queue;
import org.apache.flink.annotation.Internal;
-import org.apache.flink.streaming.api.operators.async.OperatorActions;
+import org.apache.flink.streaming.api.functions.async.ResultFuture;
+import org.apache.flink.streaming.api.operators.TimestampedCollector;
+import org.apache.flink.streaming.api.watermark.Watermark;
+import org.apache.flink.streaming.runtime.streamrecord.StreamElement;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
import org.apache.flink.util.Preconditions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayDeque;
-import java.util.Arrays;
+import java.util.ArrayList;
import java.util.Collection;
+import java.util.Deque;
import java.util.HashSet;
-import java.util.Iterator;
+import java.util.List;
+import java.util.Optional;
+import java.util.Queue;
import java.util.Set;
-import java.util.concurrent.Executor;
-import java.util.concurrent.locks.Condition;
-import java.util.concurrent.locks.ReentrantLock;
/**
- * Unordered implementation of the {@link StreamElementQueue}. The unordered
stream element queue
- * emits asynchronous results as soon as they are completed. Additionally it
maintains the
- * watermark-stream record order. This means that no stream record can be
overtaken by a watermark
- * and no watermark can overtake a stream record. However, stream records
falling in the same
- * segment between two watermarks can overtake each other (their emission
order is not guaranteed).
+ * Unordered implementation of the {@link StreamElementQueue}. The unordered
stream element queue provides
+ * asynchronous results as soon as they are completed. Additionally it
maintains the watermark-stream record order.
Review comment:
Yes. Elements within a stage could overtake each other. One more thing for
further confirmation: how to guarantee that two stages can not overtake each
other?
e.g. assuming we have four stages : {a, b, c} {watermark1} {d, e, f}
{watermark2}, and the first stage is the {a, b, c}. If the user function
completes the element `e` in third stage firstly, that means the collection of
`e` would be emitted to output before the first stage? Or I missed something
else.
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