equanz commented on code in PR #20179:
URL: https://github.com/apache/pulsar/pull/20179#discussion_r1209967970
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pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentStickyKeyDispatcherMultipleConsumers.java:
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@@ -65,23 +67,22 @@ public class PersistentStickyKeyDispatcherMultipleConsumers
extends PersistentDi
private final KeySharedMode keySharedMode;
/**
- * When a consumer joins, it will be added to this map with the current
read position.
- * This means that, in order to preserve ordering, new consumers can only
receive old
- * messages, until the mark-delete position will move past this point.
+ * When a consumer joins, it will be added to this map with the current
last sent position per the message key.
+ * This means that, in order to preserve ordering per the message key, new
consumers can only receive old
+ * messages, until the mark-delete position will move past this point in
the key. New consumers can receive
+ * any new messages with the message key that is not in the last sent
position.
*/
- private final LinkedHashMap<Consumer, PositionImpl>
recentlyJoinedConsumers;
-
- private final Set<Consumer> stuckConsumers;
- private final Set<Consumer> nextStuckConsumers;
+ private final LinkedHashMap<Consumer, LastSentPositions>
recentlyJoinedConsumers;
+ // The lastSentPosition is not thread-safe
+ private final LastSentPositions lastSentPositions;
PersistentStickyKeyDispatcherMultipleConsumers(PersistentTopic topic,
ManagedCursor cursor,
Review Comment:
Hi @poorbarcode
* [1] I think it is not entirely correct. Your scenario step seems roughly
right, but based on my analysis, the root cause of the issue is not related to
concurrency.
The cause lies in [the isDispatcherStuckOnReplays
feature](https://github.com/apache/pulsar/blob/b7f0004313ea4565717cc6d3c0b99aee5c079c6c/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentStickyKeyDispatcherMultipleConsumers.java#L429-L434),
and [the recently joined consumers
feature](https://github.com/apache/pulsar/blob/b7f0004313ea4565717cc6d3c0b99aee5c079c6c/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentStickyKeyDispatcherMultipleConsumers.java#L371-L377).
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