Re: [hibernate-dev] v6 and load-event

If/when it comes to needing that, I kind of like that continuation design. But I agree, Yoann is right - let's leave it off until needed or until we have specific requirements. Thanks everyone! On Fri, May 29, 2020 at 2:19 AM Sanne Grinovero <sanne(a)hibernate.org&gt; wrote: > On Fri, 29 May 2020 at 07:22, Yoann Rodiere <yoann(a)hibernate.org&gt; wrote: > > > > +1 not to add surround capability initially. Sounds better to start > simple and make things more complex when we actually need it :) > > Right. I didn't mean to raise additional requirements without having > investigated those tracing libraries - what I meant really is just to > raise awareness that we'll likely need to evolve it further when it > comes to finally implement such things. > > > > > Yoann Rodière > > Hibernate Team > > yoann(a)hibernate.org > > > > > > On Fri, 29 May 2020 at 07:25, Sanne Grinovero <sanne(a)hibernate.org&gt; > wrote: > >> > >> Yes, I agree. > >> > >> On Thu, 28 May 2020, 22:11 Steve Ebersole, <steve(a)hibernate.org&gt; wrote: > >>> > >>> Wanted to clarify - > >>> > >>> Regarding incremental addition of "surround listeners", so long as we > are all in agreement that this simply means there will be absolutely no > surround capability ***initially*** then I am fine with that. > >>> > >>> On Thu, May 28, 2020 at 4:10 PM Steve Ebersole <steve(a)hibernate.org&gt; > wrote: > >>>> > >>>> Hm, the dynamic enable/disable stuff should be easy to handle, no? > Depends on what specific library you are thinking of and exactly how that > detail gets propagated to us. At the end of the day, its really as simple > as protecting the creation of some of these objects with `if > (enabled)`-type checks. > >>>> > >>>> But again, if you have specific details in mind we can take a look. > >>>> > >>>> Also, I think it is not at all a good idea to even plan for > "different types of events". In fact I'm fine with getting rid of > LoadEvent completely from that contract and simply directly passing the > information that is likely useful. I mean at the end of the day a listener > for load events is going to be interested in the same set of information. > Yes, some will not need all of that information but that's not really a > concern IMO. Especially if we inline the parameters and completely avoid > the event object instantiation > >>>> > >>>> Regarding incremental addition of "surround listeners", so long as we > are all in agreement that this simply means there will be absolutely no > surround capability then I am fine with that. > >>>> > >>>> > >>>> On Thu, May 28, 2020 at 3:55 PM Sanne Grinovero < sanne(a)hibernate.org&gt; > wrote: > >>>>> > >>>>> On Thu, 28 May 2020 at 21:27, Steve Ebersole <steve(a)hibernate.org&gt; > wrote: > >>>>> > > >>>>> > Any thoughts on this "continuation" approach? > >>>>> > >>>>> I love the pattern! Maybe we'll need also some ability to not capture > >>>>> the state for events which don't have any? > >>>>> > >>>>> I wonder if that implies we'll need two different event contracts: > one > >>>>> for the listeners which need state and one for those which don't; but > >>>>> I'm not eager to overcomplicate this. > >>>>> > >>>>> > Or maybe its just not important (yet) to handle "surround" > handling? > >>>>> > >>>>> I'm confident that integration with tracing libraries would be very > >>>>> useful and interesting to have - but indeed not having time to > >>>>> research it properly I'm a bit afraid that it might need further > >>>>> changes to reach excellent performance. > >>>>> > >>>>> For example one thing I remember is that with some libraries you're > >>>>> supposed to have the option to enable/disable the profiling options > >>>>> dynamically, and since there's an expectation of no overhead when > it's > >>>>> disabled this would need to imply having a way for the overhead of > >>>>> allocating space for the captured state to "vanish": this might be a > >>>>> bit more complicated, or need to be able to take advantage of JIT > >>>>> optimisations. > >>>>> > >>>>> So if we end up thinking that such event APIs need to be different > >>>>> depending on the need for state, perhaps indeed it's better to > >>>>> postpone the design of those with state to when someone has time to > >>>>> research an optimal integration with a tracing library. It might not > >>>>> be too hard, I just haven't explored it myself yet. > >>>>> > >>>>> Maybe let's do this incrementally, considering the "continuation" > >>>>> approach a next step? > >>>>> > >>>>> Thanks, > >>>>> Sanne > >>>>> > >>>>> > > >>>>> > On Wed, May 27, 2020 at 9:27 AM Steve Ebersole < > steve(a)hibernate.org&gt; wrote: > >>>>> >> > >>>>> >> Inline... > >>>>> >> > >>>>> >> On Wed, May 27, 2020 at 8:10 AM Sanne Grinovero < > sanne(a)hibernate.org&gt; wrote: > >>>>> >>> > >>>>> >>> At high level I agree, just have 3 more thoughts: > >>>>> >>> > >>>>> >>> # Regarding the "swap" of information between listeners - could > that > >>>>> >>> even work? I might have misunderstood something, but wouldn't we > >>>>> >>> require listeners to run in some specific order for such > swapping to > >>>>> >>> work? > >>>>> >> > >>>>> >> > >>>>> >> This is why we allow control over the ordering of the registered > listeners. And yes, that is and was a hokey solution. Nothing changes > there really if that is why you are using load listener. > >>>>> >> > >>>>> >> > >>>>> >>> > >>>>> >>> # The "surround advice" you mention for e.g. timing seems very > >>>>> >>> interesting, especially as I'd love us to be able to integrate > with > >>>>> >>> tracing libraries - but these would need to be able to co-relate > the > >>>>> >>> pre-load event with some post-load event. How would that work? > I'd > >>>>> >>> expect these to need having a single listener implementation > which > >>>>> >>> implements both PreLoadEventListener and PostLoadEventListener, > but > >>>>> >>> also they'll likely need some capability to store some > information > >>>>> >>> contextual to the "event". > >>>>> >> > >>>>> >> > >>>>> >> I was just thinking through this one as well. My initial thought > was exactly what you proposed - some combination of pre/post listener with > some ability to store state between. But that gets ugly. > >>>>> >> > >>>>> >> Another option I thought about is easier to illustrate, but > basically works on the principle of "continuation" many surround advice > solutions are based on: > https://gist.github.com/sebersole/142765fe2417492061e92726e7cb6bd8 > >>>>> >> > >>>>> >> I kept the name LoadEventListener there, but since it changes the > contract anyway I'd probably rename this to something like > SurroundLoadEventListener > >>>>> >> > >>>>> >> > >>>>> >>> > >>>>> >>> # To clarify on my previous comment regarding why I'd consider > having > >>>>> >>> an actual Event class more maintainable: > >>>>> >>> Sure we won't have inline classes widely used for a while, but I > >>>>> >>> prefer planning for the long term - also we could start using > them > >>>>> >>> very soon via multi-release jars, which would simply imply that > users > >>>>> >>> on newer JDKs would see more benefits than other users. > >>>>> >>> But especially, such event instances are passed over and over > across > >>>>> >>> many methods; so in terms of maintenance and readability, such > methods > >>>>> >>> would need to pass many parameters rather than one: the example > made > >>>>> >>> above is oversimplifying our use. Also while I understand it's > >>>>> >>> unlikely, having a "cheap" event objects makes it easier to > change the > >>>>> >>> exact types being passed on. > >>>>> >>> BTW stack space is cheap but forcing many references to be > passed when > >>>>> >>> one single reference could do might also have some performance > >>>>> >>> implications since these are passed many times - I've never > tested > >>>>> >>> this scientifically though :) Inline objects would typically be > >>>>> >>> allocated on the stack as well, but they don't force the JVM to > do so. > >>>>> >>> > >>>>> >>> > >>>>> >>> Also while I said that it's unlikely we want to change those > types, > >>>>> >>> the very coming of inline types might actually encourage us to > make > >>>>> >>> changes in this area, even though these events have been stable > for > >>>>> >>> years; for example "String entityName" seems like an excellent > >>>>> >>> candidate to become "EntityName typeIdentifier" - and then allow > us to > >>>>> >>> improve the persister maps, which have been a bottleneck in the > past. > >>>>> >>> So sure we could remove them and just pass parameters, we'd just > need > >>>>> >>> to change more code if such a situation arises - I'm just > highliting > >>>>> >>> the drawbacks for our consideration, not recommending against it > :) > >>>>> >> > >>>>> >> > >>>>> >> Maybe its simply a difference of wording, but to me none of this > validates how keeping an event class is more maintainable. If you want to > say that eventually the overhead of having an actual event class will be > less, ok, but that's different. > >>>>> >> > >>>>> >> For sure though we'd have lots of uses for in-line value types > throughout the code base. Just not sure this really an argument for > keeping the event impl in-and-of-itself. > >>>>> >> > _______________________________________________ hibernate-dev mailing list hibernate-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev