I've investigated more on this issue. The `allowAutoTopicCreationType` config introduced in https://github.com/apache/pulsar/pull/4963 also brings an incompatibility but it's not serious.
I ran a standalone of Pulsar 2.5.0 (need to use JDK 8) with the following config: ``` allowAutoTopicCreationType=partitioned ``` Then I ran Pulsar client 2.5.0 and 2.4.0 to produce messages to topics that does not exist (with "http://localhost:8080"; as the service url), then list the topics: ``` "persistent://public/default/topic-2.4.0" "persistent://public/default/topic-2.5.0-partition-0" ``` The `allowAutoTopicCreationType` doesn't work for clients affected by the breaking change of #10601 and could bring unexpected behavior while a higher version (>= 2.5.0) client serves a automatically created topic by lower version clients (< 2.5.0). If `allowAutoTopicCreationForLegacyClients` is true, we should make the behavior consistent. Thanks, Yunze On Fri, Nov 18, 2022 at 12:02 PM Yunze Xu <y...@streamnative.io> wrote: > > Hi all, > > There is a breaking change for old version clients when using HTTP > lookup, see details in discussion here[1]. The affected clients I know > are: > - Java client 2.4.1 or earlier > - C++/Python clients 2.8.0 or earlier > > In short, #10601 changed the behavior for querying the partition > metadata of a topic that does not exist. > - Before: returns 0 > - After: return a TopicNotFound error, this could differ between a > non-partitioned topic and a topic that does not exist. > > Since the new getPartitionedTopicMetadata semantics have already been > used for all recent active releases (2.8 to now), it's better not to > revert #10601. Instead, I'd like to add a config to keep compatibility > for legacy clients. > > ```bash > allowAutoTopicCreationForLegacyClients=false > ``` > > If it's true, the legacy clients should be supported. > > [1] https://github.com/apache/pulsar/pull/10601#issuecomment-1319501354 > > Thanks, > Yunze
