Hi Yubiao, Thanks for driving this fix. Based on the LTS version strategy, user should able to upgrade from 3.0 to 4.0 without and compatibility issues and downgrade from 4.0 to 3.0 without any compatibility issues.
https://pulsar.apache.org/contribute/release-policy/#compatibility-between-releases So, we should also disable it by default in 4.0, but we can consider to make it as default in 5.0. And for the feature version release, user should also able to downgrade from 4.x to 3.x without any compatibility issues, so for any feature releases between 4.0 to 5.0 should also disable it by default. Cherry-pick to 3.0 sounds good to me with disabled by default, but we need to highlight in the documentation and configuration file that enabling this feature will break the backward compatibility if user wants to rollback to 2.11. Regards, Penghui On Mon, Dec 23, 2024 at 01:43 Baodi Shi <ba...@apache.org> wrote: > +1 #9292 > > > Thanks, > Baodi Shi > > Yubiao Feng <yubiao.f...@streamnative.io.invalid> 于2024年12月23日周一 11:56写道： > > > > Hi all > > > > ## Background > > PR #9292 improved the serialization for cursor metadata, which reduces > > Young GC and makes Pulsar persist more ack records of the cursor, but it > > also caused two issues below > > > > **Issue-1: Downgrade compatibility issue** > > - It changed the default implementation of cursor serialization. > > - Users can not rollback to `3.0.x` once upgraded to `4.0.x` because > > `release:3.0.x` does not contain the deserialization introduced by it, > > > > **Issue-2: It is in conflict with another config > > unackedRangesOpenCacheSetEnabled** > > - If users disabled `unackedRangesOpenCacheSetEnabled`, the cursor ack > > records will always be lost. see details > > https://github.com/apache/pulsar/pull/23759 > > > > ## Goal > > > > - Add an optional config to disable the feature that compresses cursor > > metadata, which was contributed by #9292 > > > > ``` > > cursorMetadataSerialization=V2 > > ``` > > > > - Since it reduced Young GC, I want to cherry-pick it into branch-3.0 > with > > a disabled default value. >
