On Fri, 29 May 2020 at 07:22, Yoann Rodiere <yo...@hibernate.org> 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 > yo...@hibernate.org > > > On Fri, 29 May 2020 at 07:25, Sanne Grinovero <sa...@hibernate.org> wrote: >> >> Yes, I agree. >> >> On Thu, 28 May 2020, 22:11 Steve Ebersole, <st...@hibernate.org> 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 <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
