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 <st...@hibernate.org> 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 <sa...@hibernate.org> > wrote: > >> On Thu, 28 May 2020 at 21:27, Steve Ebersole <st...@hibernate.org> 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 <st...@hibernate.org> >> wrote: >> >> >> >> Inline... >> >> >> >> On Wed, May 27, 2020 at 8:10 AM Sanne Grinovero <sa...@hibernate.org> >> 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@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev