ShivsundarR commented on code in PR #19295:
URL: https://github.com/apache/kafka/pull/19295#discussion_r2016129362
##########
clients/src/main/java/org/apache/kafka/clients/consumer/internals/ShareConsumerImpl.java:
##########
@@ -644,8 +645,12 @@ private ShareFetch<K, V> collect(Map<TopicIdPartition,
NodeAcknowledgements> ack
if (currentFetch.isEmpty()) {
final ShareFetch<K, V> fetch = fetchCollector.collect(fetchBuffer);
if (fetch.isEmpty()) {
+ // Check for any acknowledgements which could have come from
control records (GAP) and include them.
+ Map<TopicIdPartition, NodeAcknowledgements>
combinedAcknowledgements = new LinkedHashMap<>(acknowledgementsMap);
+
combinedAcknowledgements.putAll(fetch.takeAcknowledgedRecords());
+
// Fetch more records and send any waiting acknowledgements
- applicationEventHandler.add(new
ShareFetchEvent(acknowledgementsMap));
+ applicationEventHandler.add(new
ShareFetchEvent(combinedAcknowledgements));
Review Comment:
Yes :)) turns out it can.
- Some integ tests in this PR - https://github.com/apache/kafka/pull/19261
revealed that in transactions, when client receives only a control record(eg.
an abort marker) in the `ShareFetchResponse` (without any non-control record),
then in the `ShareCompletedFetch`, these control records are never
acknowledged(ideally acknowledged with GAP, indicating the client is ignoring
these control records) and are never presented to the consumer application.
- It is expected that control records are skipped and are not presented to
the application, but client should still acknowledge them with GAP
(https://github.com/apache/kafka/blob/84b8fec089682486aa9827a3baffa2513118ce6d/clients/src/main/java/org/apache/kafka/clients/consumer/internals/Acknowledgements.java#L33)
- Now these control records are usually auto acknowledged with `GAP` and
will be sent on the next `ShareFetch`/`ShareAcknowledge` request. But here as
`fetch.isEmpty()` only checks for `numRecords() == 0`, when the fetch is empty,
we actually ignore the fetch here(meaning we never acknowledge these control
records) -
https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/consumer/internals/ShareConsumerImpl.java#L598
- Now for this PR, we have added any possible acknowledgements that came in
with the empty fetch (from control records) to the `ShareFetchEvent` so that it
can be sent on the next poll().
- I agree it looks a bit odd though for readability. But yeah there is a
case when this could happen.
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