kirktrue commented on code in PR #20521:
URL: https://github.com/apache/kafka/pull/20521#discussion_r2482655989
##########
clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java:
##########
@@ -878,6 +874,108 @@ public ConsumerRecords<K, V> poll(final Duration timeout)
{
}
}
+ /**
+ * {@code checkInflightPoll()} manages the lifetime of the {@link
AsyncPollEvent} processing. If it is
+ * called when no event is currently processing, it will start a new event
processing asynchronously. A check
+ * is made during each invocation to see if the <em>inflight</em> event
has completed. If it has, it will be
+ * processed accordingly.
+ */
+ @SuppressWarnings({"CyclomaticComplexity"})
+ public void checkInflightPoll(Timer timer, boolean firstPass) {
+ // Handle the case where there's an inflight poll from the *previous*
invocation of AsyncKafkaConsumer.poll().
+ if (firstPass && inflightPoll != null) {
+ if (inflightPoll.isComplete()) {
+ Optional<KafkaException> errorOpt = inflightPoll.error();
+
+ if (errorOpt.isPresent()) {
+ // If the previous inflight event is complete, check if it
resulted in an error. If there was
+ // an error, throw it without delay.
+ log.trace("Previous inflight event {} completed with an
error, clearing", inflightPoll);
+ inflightPoll = null;
+ throw errorOpt.get();
+ } else {
+ if (fetchBuffer.isEmpty()) {
+ // If it completed without error, but without
populating the fetch buffer, clear the event
+ // so that a new event will be enqueued below.
+ log.trace("Previous inflight event {} completed
without filling the buffer, clearing", inflightPoll);
+ inflightPoll = null;
+ } else {
+ // However, if the event completed, and it populated
the buffer, *don't* create a new event.
+ // This is to prevent an edge case of starvation when
poll() is called with a timeout of 0.
+ // If a new event was created on *every* poll, each
time the event would have to complete the
+ // validate positions stage before the data in the
fetch buffer is used. Because there is
+ // no blocking, and effectively a 0 wait, the data in
the fetch buffer is continuously ignored
+ // leading to no data ever being returned from poll().
+ log.trace("Previous inflight event {} completed and
filled the buffer, not clearing", inflightPoll);
+ }
+ }
+ } else if (time.milliseconds() >= inflightPoll.deadlineMs() &&
inflightPoll.isValidatePositionsComplete()) {
Review Comment:
Added an `isExpired()` method to `AsyncPollEvent`.
##########
clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java:
##########
@@ -878,6 +874,108 @@ public ConsumerRecords<K, V> poll(final Duration timeout)
{
}
}
+ /**
+ * {@code checkInflightPoll()} manages the lifetime of the {@link
AsyncPollEvent} processing. If it is
+ * called when no event is currently processing, it will start a new event
processing asynchronously. A check
+ * is made during each invocation to see if the <em>inflight</em> event
has completed. If it has, it will be
+ * processed accordingly.
+ */
+ @SuppressWarnings({"CyclomaticComplexity"})
Review Comment:
I refactored `checkInflightPoll()` and pulled out
`maybeClearPreviousInflightPoll()` and `maybeClearCurrentInflightPoll()` helper
methods. PTAL.
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