Pulsar negative acked messages in Shared Subscription sometimes doesn't get redelivered

[suvrajit94]

I am using Pulsar Java Client 2.9.3. Seeing intermittent redelivery issues when message is negative acknowledged. The topic is non-partitioned, but multi-AZ. Using receiver queue size 0 in consumer client, according to the code, messages should get dispatched immediately to next available consumers.

According to broker logs, the message is not dispatched after being negative ack.

Thanks in advance.

[lhotari]

There are thousands of improvements and fixes since 2.9.3, including a large number of critical security fixes. Please upgrade your Pulsar Java client to a supported version. What Pulsar broker version are you using?
You can find supported versions at https://pulsar.apache.org/contribute/release-policy/.

[lhotari]

One detail is that if the message has already been acknowledged, negatively acknowledging the message is a no-op. This is explained in this comment: #23436 (comment).