pnowojski commented on a change in pull request #9383: [FLINK-13248] [runtime]
Adding processing of downstream messages in AsyncWaitOperator's wait loops
URL: https://github.com/apache/flink/pull/9383#discussion_r314654570
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File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/AbstractStreamOperator.java
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@@ -232,6 +233,24 @@ public void setup(StreamTask<?, ?> containingTask,
StreamConfig config, Output<S
stateKeySelector2 = config.getStatePartitioner(1,
getUserCodeClassloader());
}
+ /**
+ * Allows downstream operators in the operator chain to process of
events.
+ * <p>This method should be called whenever an operator would need to
block the task thread to wait for output
+ * buffers to flush.</p>
+ * <p>If such an operator would indeed block the task thread, deadlocks
can arise when two such operators are
+ * chained.</p>
+ * <p>It's up to the implementor of the operator to find a good
trade-off, between yielding and own processing.
+ * If the operator never blocks the task thread during input
processing, this method should not be called at
+ * all.</p>
+ * <p>This method indicates whether downstream events actually have
been processed, which can be used to issue
+ * further invocations.</p>
+ *
+ * @return true if any downstream event has been handled.
+ */
+ protected boolean yieldToDownstream() {
+ throw new NotImplementedException("API draft");
Review comment:
I'm just not sure how to expose it to the users.
Instead of `AbstractStreamOperator#yield()` we could have
`StreamOperator#yield()`, or `StreamTask#yield()`. For the last one,
`StreamTask` is accessible via `SetupableStreamOperator#setup()` and
`StreamOperatorFactory#createStreamOperator()` methods.
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