> If you mean `msg.getTopicName()`, how can you declare it's better than > `msgId.getOwnerTopic()`?
> It can. Because the `TopicMessageIdImpl` already contains the correct > topic. That's the point. ``` var msgId = (TopicMessageId) multiTopicsConsumer.getMessageId(); ``` if `msgId.getOwnerTopic()` is the interface of `MessageId`, I have no problem. but it needs to cast the `TopicMessageId` from `MessageId`, which is very user-unfriendly. And it doesn't make sense. > I don't know what you're thinking about using > `consumer.seek(msg.getTopicName(), msg.getMessageId()` for a single > topic consumer. If it's accepted, and you want to unify the use case > of `seek`, the original `seek` API should be deprecated and much > existing code could be affected. If it's not accepted, users have to > distinguish if a consumer is a multi-topics consumer. the same as `consumer.seek(TopicMessageId topicMessageId)` for a single topic consumer is also strange. My point is either TopicName belongs to MessageId or separate the two. it's not a good interface implementation to couple them together. Very unclear. Thanks, Bo Yunze Xu <y...@streamnative.io.invalid> 于2022年12月21日周三 22:46写道： > > > If messageID does not contain `TopicName`, the `TopicName` is best get from > > msg. > > If you mean `msg.getTopicName()`, how can you declare it's better than > `msgId.getOwnerTopic()`? > > > but it still cannot avoid `TopicName` for marking this `MessageID` belongs > > to this topic. > > It can. Because the `TopicMessageIdImpl` already contains the correct > topic. That's the point. > > > if using `TopicMessageId` also has the same problem, why we need to use > > `TopicMessageId` not `MessageId` > > Because `TopicMessageId` is constructed by the Pulsar Client library > itself, which can guarantee `getOwnerTopic()` returns the correct > topic name. The benefit of passing a `TopicMessageId` rather than the > combination of a topic name and a `MessageId` is, users won't need to > care about how to get the correct topic name for a given partition by > themselves. > > The key point is that if there is only one valid value for an > argument, which relies on the other argument, then the API design is > bad. Assume you need to use the Pulsar client like: > > ``` > // numberOfMessages must be the same with msgIds.size(), otherwise, an > exception will be thrown > consumer.acknowledge(numberOfMessages, msgIds); > ``` > > With the API of this proposal, users don't need to care much about how > to call `seek` correctly, except the MessageId is returned by > Producer#send. `consumer.seek(msg.getMessageId())` works for all > cases. > > With the `seek(String, MessageId)` API, you have to write more > explanations like: > 1. If the consumer only subscribes to a topic, use > `consumer.seek(msg.getMessageId())`. > 2. If the consumer subscribes to multiple topics, use > `consumer.seek(topic, msg.getMessageId())`. The topic must be what the > message belongs to, so you have to use the correct topic like > `consumer.seek(msg.getTopicName(), msg.getMessageId()`. Otherwise, > seek would fail. > > I don't know what you're thinking about using > `consumer.seek(msg.getTopicName(), msg.getMessageId()` for a single > topic consumer. If it's accepted, and you want to unify the use case > of `seek`, the original `seek` API should be deprecated and much > existing code could be affected. If it's not accepted, users have to > distinguish if a consumer is a multi-topics consumer. > > Thanks, > Yunze > > On Wed, Dec 21, 2022 at 8:50 PM 丛搏 <bog...@apache.org> wrote: > > > > Hi, Yunze: > > > > < ```java > > < var msg = multiTopicsConsumer.receive(); > > < var msgId = (TopicMessageId) multiTopicsConsumer.getMessageId(); > > < consumer.seek(msgId.getOwnerTopic(), msgId); > > < ``` > > > > the code can be like this: > > ```java > > var msg = anyConsumer.receive(); > > var msgId = anyConsume.getMessageId(); > > consumer.seek(msg, msgId); > > ``` > > If messageID does not contain `TopicName`, the `TopicName` is best get from > > msg. > > > > < What's different is that the offset in Kafka can represent a position > > < of ANY partition, while the MessageId in Pulsar can only represent the > > < position of A SPECIFIC partition. > > > > Although MessageId in Pulsar can only represent the position of A > > SPECIFIC partition, but it still needs a TopicName. `LedgerID` and > > `EntryID` do not mean that this `MessageID` belongs to a topic > > (although it does belong), but it still cannot avoid `TopicName` for > > marking this `MessageID` belongs to this topic. > > > > > And in Pulsar, we also do not expose > > > the partition concept, if we introduce the seek API with the topic > > > name as the argument, we have to explain in detail about what's the > > > topic name for a partition. It could be a very confusing thing from my > > > experience when I explained the "partition" concept in community. > > > > if using `TopicMessageId` also has the same problem, why we need to > > use `TopicMessageId` not `MessageId` > > > > Thanks, > > Bo > > > > Yunze Xu <y...@streamnative.io.invalid> 于2022年12月21日周三 16:59写道： > > > > > > Hi Bo, > > > > > > If we have the `seek` API that accepts a topic name, how to use seek > > > for a single topic consumer and multi-topics consumer will be > > > different. > > > > > > ```java > > > var msg = singleTopicConsumer.receive(); > > > var msgId = singleTopicConsumer.getMessageId(); > > > consumer.seek(msgId); > > > ``` > > > > > > ```java > > > var msg = multiTopicsConsumer.receive(); > > > var msgId = (TopicMessageId) multiTopicsConsumer.getMessageId(); > > > consumer.seek(msgId.getOwnerTopic(), msgId); > > > ``` > > > > > > It's not as clear as you have thought. A question could come from the > > > code above: since we can get the key (topic name) from `msgId` itself, > > > why do we need another argument? > > > > > > What's worse is that users have to specify the correct topic name. For > > > a partitioned topic, if users specified another partition, the `seek` > > > operation would fail. If they specified something like > > > `multiTopicsConsumer.getTopic()`, it would also fail because other > > > APIs like `Consumer#getTopic()` doesn't return the correct topic name. > > > > > > If there is only one correct topic name for a given TopicMessageId, > > > what's the meaning of making it as a required argument? > > > > > > BTW, let's see Kafka client's commit API: > > > > > > ```java > > > public void commitSync(Map<TopicPartition,OffsetAndMetadata> offsets) > > > ``` > > > > > > What's different is that the offset in Kafka can represent a position > > > of ANY partition, while the MessageId in Pulsar can only represent the > > > position of A SPECIFIC partition. And in Pulsar, we also do not expose > > > the partition concept, if we introduce the seek API with the topic > > > name as the argument, we have to explain in detail about what's the > > > topic name for a partition. It could be a very confusing thing from my > > > experience when I explained the "partition" concept in community. > > > > > > Thanks, > > > Yunze > > > > > > > > > On Wed, Dec 21, 2022 at 3:20 PM 丛搏 <bog...@apache.org> wrote: > > > > > > > > Hi Yunze, > > > > > > > > add `TopicMessageId ` will couple messageID and `topic name` together, > > > > which is very unclear for non-partition-topic. > > > > > > > > ``` > > > > void seek(String topicName, MessageId messageId) throws > > > > PulsarClientException; > > > > List<Map<String, MessageId>> getLastTopicMessageId() throws > > > > PulsarClientException; > > > > ``` > > > > If the interface is designed in this way, it may be simpler, easier to > > > > understand, and more intuitive for users, and MessageID will not be > > > > coupled with TopicName. > > > > > > > > because this PIP has already initiated a VOTE, so I will sync this > > > > reply to PIP-224-VOTE[0] > > > > > > > > Thanks, > > > > Bo > > > > [0] https://lists.apache.org/thread/mbrpjsgrgwrlkdpvkk738jxnlk7rf4qk > > > > > > > > Yunze Xu <y...@streamnative.io.invalid> 于2022年12月9日周五 14:33写道： > > > > > > > > > > Hi Jiaqi, > > > > > > > > > > Let's move to > > > > > https://lists.apache.org/thread/mbrpjsgrgwrlkdpvkk738jxnlk7rf4qk > > > > > for the vote. > > > > > > > > > > Thanks, > > > > > Yunze > > > > > > > > > > On Fri, Dec 9, 2022 at 1:54 PM Jiaqi Shen <gleiphir2...@gmail.com> > > > > > wrote: > > > > > > > > > > > > This is make sense to me, +1 > > > > > > > > > > > > Thanks, > > > > > > Jiaqi Shen > > > > > > > > > > > > > > > > > > Yunze Xu <y...@streamnative.io.invalid> 于2022年12月7日周三 13:51写道： > > > > > > > > > > > > > Hi Baodi, > > > > > > > > > > > > > > I decided not to change the behavior of the `negativeAcknowledge` > > > > > > > method. I just checked again that there is no exception signature > > > > > > > for > > > > > > > this method and there is no asynchronous version like > > > > > > > `negativeAcknowledgeAsync`. To keep the API compatible, we should > > > > > > > not > > > > > > > add an exception signature, which would be required if a > > > > > > > `PulsarClientException` was thrown. > > > > > > > > > > > > > > Thanks, > > > > > > > Yunze > > > > > > > > > > > > > > On Tue, Nov 29, 2022 at 10:12 PM Baodi Shi > > > > > > > <baodi....@icloud.com.invalid> > > > > > > > wrote: > > > > > > > > > > > > > > > > Hi, Yunze: > > > > > > > > > > > > > > > > Thanks for your proposal. That Looks good to me. > > > > > > > > > > > > > > > > `negativeAcknowledge` also needs to add the same checks as the > > > > > > > > new > > > > > > > acknowledge interface. > > > > > > > > > > > > > > > > > This interface doesn't add any acknowledge overload because > > > > > > > > > the > > > > > > > overloads are already too many. But it will make the behavior > > > > > > > clear. > > > > > > > > I think since we exposed the TopicMessageId, it would be better > > > > > > > > to add > > > > > > > overloaded interfaces (even if the overloads are a lot). This can > > > > > > > users to > > > > > > > clearly associate the use cases of MultiTopicConsumer and > > > > > > > TopicMessageId. > > > > > > > > > > > > > > > > Also, while it's okay to use TopicMessageId param on a single > > > > > > > > consumer, > > > > > > > I guess we shouldn't allow users to use it. > > > > > > > > > > > > > > > > In this way, users are clearly aware that TopicMessageId is > > > > > > > > used when > > > > > > > using MultiTopicConsumer and MessageId is used when using > > > > > > > SingleTopicConsumer.(Maybe it's not a good idea) > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > Baodi Shi > > > > > > > > > > > > > > > > > 2022年11月29日 15:57，Yunze Xu <y...@streamnative.io.INVALID> 写道： > > > > > > > > > > > > > > > > > >> 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 > > > > > > > > > > > > > > >
