Good suggestion. We can try that.

Thanks,
Yunze

On Fri, Jul 14, 2023 at 7:03 PM Lari Hotari <lhot...@apache.org> wrote:
>
> Makes sense. We should use tooling in CI to enforce binary
> compatibility of the modules that shouldn't break.
> There's japicmp [1] that can be used to do this. japicmp comes with a
> maven plugin [2] that needs to be configured with the rules to be
> used.
>
> -Lari
>
> 1 - https://siom79.github.io/japicmp/
> 2 - https://siom79.github.io/japicmp/MavenPlugin.html
>
> On Fri, Jul 14, 2023 at 1:55 PM Yunze Xu <x...@apache.org> wrote:
> >
> > Hi all,
> >
> > As the Pulsar community is growing, the core project could be depended
> > on by many ecosystem projects, including protocol handlers and
> > connectors. However, there is no clear API compatibility guarantee at
> > the moment.
> >
> > For now, PIP is required when public APIs change [1]. However, I think
> > the public API only refers to the interfaces in:
> > - The pulsar-client-api module
> > - The pulsar-admin-api module
> > - Any plugin interface, e.g. ProtocolHandler
> >
> > However, when a 3rd party project adds Pulsar as the dependency, it's
> > legal and common to use any public class and any public method from
> > it. For a specific example, just as I've discussed many times, the
> > MessageId interface from the pulsar-client-api module, the 3rd party
> > project tends to cast it to the specific implementation (e.g.
> > MessageIdImpl) to use.Then the challenge comes, if we modifies any
> > public method of MessageIdImpl, the ecosystem developer could suffer
> > from it.
> >
> > For this case, we have no clear rule on how Pulsar guarantees the API
> > compatibility. So I'd like to propose my suggestion here, once it
> > reaches the consensus, I will write a formal proposal and add it to
> > our contribution guide [2].
> >
> > Here are my proposed rules (I will add specific examples for a formal 
> > proposal):
> > 1. For any new interface, add the
> > org.apache.pulsar.common.classification.InterfaceStability
> > 2. For patch releases, e.g. 3.0.x to 3.0.y, we should never introduce
> > any public method change.
> > 3. For minor releases, e.g. 3.1.0 to 3.2.0, when you want to modify a
> > public method, e.g. `foo(int, int)` is changed to `foo(int, String)`,
> > don't remove the original `foo(int, int)` method. Instead, add the
> > `@Deprecated` annotation and keep the semantics not changed if
> > possible.
> > 4. Any public method with the `@Deprecated` annotation can be removed
> > in the next minor release.
> > 5. The rules above are applied to all modules, not only the xxx-api modules.
> >
> > With the rules above,
> > -  For ecosystem developers, they can know the risk to use any public
> > method from a class, especially implementation class. They can also be
> > confident that no API will change if they upgrade Pulsar from a.b.c to
> > a.b.d.
> > - For committers, they should be more careful to review the PRs that
> > introduce API changes.
> > - For release managers, it would be clear that any PR that changes any
> > public method should not be cherry-picked to release branches.
> >
> > [1] https://github.com/apache/pulsar/tree/master/pip#when-is-a-pip-required
> > [2] https://pulsar.apache.org/contribute/
> >
> > Thanks,
> > Yunze

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