> Is there a case where the user uses the messageId returned by the producer to seek in the consumer? Is this a good behavior?
Yes. I think it should be acceptable. To correct my previous point, now I think the MessageId returned by send should also be able to be applied for seek or acknowledge. > even with the current proposal, it may return null when getting the topic from TopicMessageId for backward compatibility. No. It may return null just because Java doesn't allow a non-null returned value. The internal implementations of TopicMessageId#getOwerTopic should return a non-null topic name to avoid null check. When I mentioned **the implementation of getTopicName() must return null**, the assumption is that MessageId#toByteArray serializes the topic name if adding the `getTopicName()` method. However, in this proposal, `TopicMessageId#toByteArray` won't. See the implementation of `TopicMessageId#create`. It's only a wrapper for an arbitrary MessageId implementation. Thanks, Yunze On Tue, Nov 29, 2022 at 2:47 PM Zike Yang <z...@apache.org> wrote: > > Hi Yunze, > > Thanks for your proposal. Quoted from your GitHub comments[0]: > > > There is also a case when MessageId is returned from Producer#send. In this > > case, the returned MessageId should only used for serialization > > Is there a case where the user uses the messageId returned by the > producer to seek in the consumer? Is this a good behavior? > > > If we added the method directly to MessageId, to keep the backward > > compatibility, the implementation of getTopicName() must return null, which > > is not a good design. > > I think it's a trade-off. If I understand correctly, even with the > current proposal, it may return null when getting the topic from > TopicMessageId for backward compatibility. The current > TopicMessageIdImpl doesn't serialize the topic information. > > > [0] https://github.com/apache/pulsar/issues/18616#issuecomment-1328609346 > > Thanks, > Zike Yang > > On Mon, Nov 28, 2022 at 12:22 PM Yunze Xu <y...@streamnative.io.invalid> > wrote: > > > > Hi all, > > > > I've opened a PIP to discuss: https://github.com/apache/pulsar/issues/18616. > > > > The consumer's MessageId related APIs have some hidden requirements > > and flakiness and some behaviors are not documented well. This > > proposal will introduce a TopicMessageId interface that exposes a > > method to get a message's owner topic. > > > > P.S. There was an email [1] that didn't add the "[DISCUSS]" label, > > which might be a little confusing. So I sent the email again for > > discussion. Please do not reply to the previous email. > > > > [1] https://lists.apache.org/thread/6gj16pmrjk6ncsd30xrl20pr5ng6t61o > > > > Thanks, > > Yunze
