enableRetry default & question on retry behaviour

[joshua-motorq]

1. Is Retry Letter Topic only supported in Shared subscription mode?
2. Broker sends message to consumer 1, Consumer 1 fails to ACK beyond timeout, Broker resends message to consumer 2. Would this message have RECONSUMEDTIMES property defined? (is this message considered to be retried?)
3. what is the default value of enaleRetry property?
4. is enableRetry need to be set to true to enable retry letter topic and tracking of RECONSUMEDTIMES?

[joshua-motorq]

Answered Q3 myself

By default, automatic retry is disabled. You can set enableRetry to true to enable automatic retry on the consumer.
https://pulsar.apache.org/docs/4.0.x/concepts-messaging/#retry-letter-topic

[lhotari]

1. Is Retry Letter Topic only supported in Shared subscription mode?

retry letter topic is implemented in the Pulsar client. For example, for the Pulsar Java client, there was a recent change that internally the consumer for the retry letter topic will always use a shared subscription addressing issues with other subscription types.
#23859

2. Broker sends message to consumer 1, Consumer 1 fails to ACK beyond timeout, Broker resends message to consumer 2. Would this message have RECONSUMEDTIMES property defined? (is this message considered to be retried?)

No, RECONSUMEDTIMES wouldn't have been incremented in that case. The transient redeliveryCount property would be incremented in this case. This is due to the implementation detail that RECONSUMEDTIMES is stored in message properties (headers) and the retry letter topic feature is completely a client side implementation.

3. what is the default value of enableRetry property?

false

4. is enableRetry need to be set to true to enable retry letter topic and tracking of RECONSUMEDTIMES?

yes.

Just adding that in case of consumers not acknowledging messages or disconnecting, the broker will increment the redeliveryCount property. That is completely independent of the retry letter topic feature. The redeliveryCount information is not persisted and it resets to 0 in certain cases.

[joshua-motorq]

The redeliveryCount information is not persisted and it resets to 0 in certain cases.

@lhotari Is it correct to undersatnd that redeliveryCount is not reliably accurate?

Thank you for the other answers, Got all the clarity needed!