liangyepianzhou commented on PR #20927:
URL: https://github.com/apache/pulsar/pull/20927#issuecomment-1717091753
> > During the process of creating a subscription, when checking if the
transaction pending has been initialized using return store.exists(PREFIX +
path);, a connection failure error occurred while connecting to ZooKeeper.
However, the created subscription continues to exist in the PersistentTopic,
which causes subsequent retries to keep using the same subscription.
>
> @liangyepianzhou In such a scenario, the "subscribe" command should be
deemed unsuccessful. The PendingAck module, being a part of the system, should
focus solely on cleaning up its own state and subsequently notifying the caller
of the failure it encountered. Then the caller("subscribe") should cleanup it's
own state.
This process can happen in loading or creating persistent topics, and the
method `createPersistentSubscription` does not concern the errors that happened
in constructing PersistentSubscription. So it's not easy for us to fail the
caller.
```java
private PersistentSubscription createPersistentSubscription(String
subscriptionName, ManagedCursor cursor,
boolean replicated, Map<String, String> subscriptionProperties) {
requireNonNull(topicCompactionService);
if (isCompactionSubscription(subscriptionName)
&& topicCompactionService instanceof
PulsarTopicCompactionService pulsarTopicCompactionService) {
CompactedTopicImpl compactedTopic =
pulsarTopicCompactionService.getCompactedTopic();
return new PulsarCompactorSubscription(this, compactedTopic,
subscriptionName, cursor);
} else {
return new PersistentSubscription(this, subscriptionName,
cursor, replicated, subscriptionProperties);
}
}
```
We can just reload the subscription to load PendingAck again.
Whether it is the broker initiating a retry or returning an exception to the
client side, which then triggers a retry, the result is identical. Users are
oblivious to this, as we do not throw retryable exceptions to the users.
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