Thanks for the clarification. "regardless of the method visibility/stability" confused me for a bit.
On Fri, Oct 28, 2016 at 10:31 AM, Sangjin Lee <[email protected]> wrote: > No, private methods are free to change as far as the class contract is > concerned. > > On Fri, Oct 28, 2016 at 10:30 AM, Ravi Prakash <[email protected]> > wrote: > >> Would this mean that if there is a private method in MyPublicStableClass, >> changing which wouldn't break anything, could we still not change it? >> >> On Thu, Oct 27, 2016 at 2:55 PM, Sangjin Lee <[email protected]> wrote: >> >> > Resurrecting an old thread as part of the YARN bug bash (YARN-5130). >> > >> > At minimum, I believe we agree to the following (do let me know if that >> is >> > not the case): >> > (1) If the class is declared Public/Stable, no changes to the class that >> > breaks the Stable contract should be made between non-major releases >> > **regardless >> > of the method visibility/stability**. For example, the following would >> > break the stability: >> > - adding a new abstract method, whether that method is stable, >> evolving, or >> > even private >> > - renaming a public method >> > Although it may be possible to have methods with weaker >> > stability/visibility, they still MUST not break the class contract. >> > >> > (2) We need to address the existing violations to ContainerStatus and >> > NodeReport by adding a default implementation for **minor releases**. >> > - ContainerStatus: YARN-3866 (2.8) >> > - NodeReport: YARN-4293 (2.8) >> > >> > There are subsequent changes to ContainerStatus by YARN-2882 and >> YARN-5430, >> > but they are marked 2.9.0. Is there going to be 2.9.0? If not, then >> these >> > might not matter as 3.0.0 permits backward incompatible changes. >> > >> > Thoughts? >> > >> > On Tue, May 31, 2016 at 10:48 AM, Sangjin Lee <[email protected]> wrote: >> > >> > > >> > > >> > > On Tue, May 31, 2016 at 10:10 AM, Chris Nauroth < >> > [email protected]> >> > > wrote: >> > > >> > >> I recommend that we update the compatibility guide with some text >> that >> > >> explicitly addresses subclassing/interface inheritance stability for >> > >> classes/interfaces annotated Stable. This is for our own benefit >> too. >> > (I >> > >> often refer back to that doc when I'm coding a patch that might have >> a >> > >> chance of being backwards-incompatible.) >> > >> >> > > >> > > I agree that making this distinction helps not only users but also the >> > > hadoop contributors. In addition to updating the compatibility guide, >> how >> > > about adding a new audience annotation for interfaces & abstract >> classes >> > > that spells out whether a 3rd-party is expected to extend/implement >> it? >> > > >> > > For example, some interface can be Public/Stable for use but could be >> > > off-limits in terms of extending/implementing it, while another can be >> > > Public/Stable for use and allowed to be extended but with an Evolving >> > > stability. It requires a little design, but should helps us a great >> deal >> > on >> > > both ends. My 2 cents. >> > > >> > > Sangjin >> > > >> > > >> > >> >> > >> --Chris Nauroth >> > >> >> > >> >> > >> >> > >> >> > >> On 5/31/16, 9:46 AM, "Karthik Kambatla" <[email protected]> wrote: >> > >> >> > >> >Argh! Totally my bad on YARN-2882. Kept missing the changes to >> > >> >ContainerStatus even after you pointed out. >> > >> > >> > >> >Filed YARN-5184 to fix this before we release it. Thanks for >> pointing >> > it >> > >> >out, Steve. >> > >> > >> > >> >On Tue, May 31, 2016 at 6:00 AM, Steve Loughran < >> > [email protected]> >> > >> >wrote: >> > >> > >> > >> >> >> > >> >> On 31 May 2016, at 05:44, Karthik Kambatla <[email protected] >> > <mailto: >> > >> >> [email protected]>> wrote: >> > >> >> >> > >> >> Inline. >> > >> >> >> > >> >> On Sat, May 28, 2016 at 11:34 AM, Sangjin Lee <[email protected] >> > >> <mailto: >> > >> >> [email protected]>> wrote: >> > >> >> I think there is more to it. The InterfaceStability javadoc >> states: >> > >> >> Incompatible changes must not be made to classes marked as >> > stable. >> > >> >> >> > >> >> And in practice, I don't think the class annotation can be >> > considered a >> > >> >> simple sum of method annotations. There is a notion of class >> > >> >>compatibility >> > >> >> distinct from method stability. One key example is interfaces and >> > >> >>abstract >> > >> >> classes as in this case. The moment a new abstract method is >> added, >> > the >> > >> >> class becomes incompatible as it would break all downstream >> > subclasses >> > >> >>or >> > >> >> implementing classes. That's the case even if *all methods are >> > declared >> > >> >> stable*. Thus, adding any abstract method (no matter what their >> > >> >> scope/stability is) should be considered in violation of the >> stable >> > >> >> contract of the class. >> > >> >> >> > >> >> Fair point. I was referring to them in the context of adding >> > @Evolving >> > >> >> methods to @Stable classes. Our policy states that "Classes not >> > >> >>annotated >> > >> >> are implicitly ³Private². Class members not annotated inherit the >> > >> >> annotations of the enclosing class." So, the annotation on a >> method >> > >> >> overrides that of the enclosing class. This seems pretty >> reasonable >> > to >> > >> >>me. >> > >> >> >> > >> >> >> > >> >> >> > >> >> My code wouldn't even compile because new abstract methods were >> added >> > >> >>to a >> > >> >> class tagged as stable. >> > >> >> >> > >> >> As far as I'm concerned, it doesn't meat the strict semantics of >> > >> >>"stable", >> > >> >> unless there is some nuance I'm missing. >> > >> >> >> > >> >> Therefore, I'm with Sangin: adding new abstract methods to an >> > existing >> > >> >> @Stable class breaks compatibility. Adding new non-abstract >> methods >> > >> >>‹fine. >> > >> >> It would have been straightforward to add some new methods to, say >> > >> >> ContainerReport, which were no-ops/exception raising, but which at >> > >> least >> > >> >> didn't break compilation. (though they may have broken codepaths >> > which >> > >> >> required the methods to act as getters/settes) >> > >> >> >> > >> >> Do you think there is reason to revisit this? If yes, we should >> > update >> > >> >> this for Hadoop 3. >> > >> >> >> > >> >> I'm not sure about revisiting. I'm raising the fact that changes >> to >> > >> >> classes marked as stable have broken code, and querying the >> validity >> > of >> > >> >> such an operation within the constraints of the 2.x codebase. >> > >> >> >> > >> >> And I'm raising it on yarn-dev, as that's where things broke. If >> we >> > do >> > >> >> want to revisit things, that'll mean a move to common-dev. >> > >> >> >> > >> >> >> > >> >> >> > >> >> Regarding interfaces and abstract classes, one future enhancement >> to >> > >> the >> > >> >> InterfaceStability annotation we could consider is formally >> > separating >> > >> >>the >> > >> >> contract for users of the API and the implementers of the API. >> They >> > >> >>follow >> > >> >> different rules. It could be feasible to have an interface as >> > >> >>Public/Stable >> > >> >> for users (anyone can use the API in a stable manner) but Private >> for >> > >> >> implementers. The idea is that it is still a public interface but >> no >> > >> >> third-party code should not subclass or implement it. I suspect a >> > fair >> > >> >> amount of hadoop's public interface might fall into that category. >> > That >> > >> >> itself is probably an incompatible change, so we might have to >> wait >> > >> >>until >> > >> >> after 3.0, however. >> > >> >> >> > >> >> Interesting thought. Agree that we do not anticipate users >> > sub-classing >> > >> >> most of our Public-Stable classes. >> > >> >> >> > >> >> There are also classes which we do not anticipate end-users to >> > directly >> > >> >> use, but devs might want to sub-class. This applies to pluggable >> > >> >>entities; >> > >> >> e.g. SchedulingPolicy in fairscheduler. We are currently using >> > >> >> Public-Evolving to capture this intent. >> > >> >> >> > >> >> Should we add a third annotation in addition to Audience and >> > Stability >> > >> >>to >> > >> >> capture whether a class can be extended? Given the few classes we >> > >> >> anticipate being extended, this is likely lesser work. :) >> > >> >> >> > >> >> >> > >> >> Some options. >> > >> >> >> > >> >> -add a specific @PluginPoint extension with different stability >> > >> >> requirements.(stable, unstable, evolving). That tells implementors >> > how >> > >> >> likely things are to break. >> > >> >> >> > >> >> -Add some interface to indicate really, really, unstable. That >> comes >> > up >> > >> >> more with things like the Async FS APIs, where the discussion >> there >> > is >> > >> >> about how it may change radically. >> > >> >> >> > >> >> Something like @Experimental could be that. That means not just >> "can >> > >> >> change" but "can go away" >> > >> >> >> > >> >> > >> >> > >> ------------------------------------------------------------ >> --------- >> > >> To unsubscribe, e-mail: [email protected] >> > >> For additional commands, e-mail: [email protected] >> > >> >> > >> >> > > >> > >> > >
