----- Original Message -----
From: "Tomas Jelinek" <tjelinek@redhat.com> To: awels@redhat.com Cc: "Oved Ourfali" <ovedo@redhat.com>, "Liran Zelkha" <lzelkha@redhat.com>, devel@ovirt.org Sent: Wednesday, June 3, 2015 9:58:34 AM Subject: Re: [ovirt-devel] hibernate's internal PersistentBag sent to FE
----- Original Message -----
From: "Alexander Wels" <awels@redhat.com> To: "Oved Ourfali" <ovedo@redhat.com> Cc: "Tomas Jelinek" <tjelinek@redhat.com>, "Liran Zelkha" <lzelkha@redhat.com>, devel@ovirt.org Sent: Tuesday, June 2, 2015 3:28:35 PM Subject: Re: [ovirt-devel] hibernate's internal PersistentBag sent to FE
On Tuesday, June 02, 2015 09:10:38 AM Oved Ourfali wrote:
----- Original Message -----
From: "Tomas Jelinek" <tjelinek@redhat.com> To: awels@redhat.com Cc: "Liran Zelkha" <lzelkha@redhat.com>, "Oved Ourfali" <ovedo@redhat.com>, devel@ovirt.org Sent: Tuesday, June 2, 2015 4:08:05 PM Subject: Re: [ovirt-devel] hibernate's internal PersistentBag sent to FE
----- Original Message -----
From: "Alexander Wels" <awels@redhat.com> To: "Liran Zelkha" <lzelkha@redhat.com> Cc: "Tomas Jelinek" <tjelinek@redhat.com>, "Oved Ourfali" <ovedo@redhat.com>, devel@ovirt.org Sent: Tuesday, June 2, 2015 2:51:31 PM Subject: Re: [ovirt-devel] hibernate's internal PersistentBag sent to FE
On Tuesday, June 02, 2015 03:05:11 AM Liran Zelkha wrote:
----- Original Message -----
> From: "Tomas Jelinek" <tjelinek@redhat.com> > To: "Oved Ourfali" <ovedo@redhat.com> > Cc: awels@redhat.com, "Liran Zelkha" <lzelkha@redhat.com>, > devel@ovirt.org > Sent: Tuesday, June 2, 2015 9:59:17 AM > Subject: Re: [ovirt-devel] hibernate's internal PersistentBag > sent > to > FE > > > > ----- Original Message ----- > > > From: "Oved Ourfali" <ovedo@redhat.com> > > To: awels@redhat.com > > Cc: "Liran Zelkha" <lzelkha@redhat.com>, devel@ovirt.org > > Sent: Tuesday, June 2, 2015 8:35:56 AM > > Subject: Re: [ovirt-devel] hibernate's internal PersistentBag > > sent > > to > > FE > > > > top-posting: > > Due to the fact that we'll see that all over the place, I > > really > > think > > that > > it would be best to support that at the frontend level, and not > > the > > backend > > level. > > well, from philosophical perspective I think that sending > org.hibernate.collection.**internal**.PersistentBag from backend > to > FE > and > than faking it's implementation on FE > is a way to hell. It will bring lots of problems. For example the > FE > will > be directly dependent on the internal structure of an internal > hibernate > class and if we update hibernate, FE can fail miserably. > Also the FE patch (https://gerrit.ovirt.org/#/c/41682/1) seems to > be > more > tricky than expected - it seems to be working but Omer had issues > with > it > and in some cases (when the delegating also retainAll()) it > caused > my > JRE > to fail on SIGSEGV. > It can be fixed on FE but it is a hack with all risks this kinds > of > hacks > brings.
I don't think it really matters where we do it, as long as server code will still use the PersistentBag (otherwise we won't be able to use attached entities, and performance will suffer). I believe that serializing these objects to JSON/XML - will work, we won't need to do 2 level of conversions (PersistentBag-->List-->JSON/XML). So if the issue is only on the GWT side, and we won't to write this code once, and not per entity - where is the best way to put it?
The original problem comes from the fact that we are serializing an object from the backend to the frontend that the frontend cannot handle (The persistent bag). This is a backend implementation detail that the frontend really doesn't care about. In essence GWT is Javascript that is made to look like Java, but it has a bunch of limitations due to the fact it still ends up as javascript in the end.
> > Doing it in the backend level will cause a lot of overhead. > > Is it really lots of overhead? Comparing to all other layers the > data > has > to pass anyway? When abandoning GWT FE and start to use REST we > will > anyway remove the GenericApiGWTServiceImpl which contains this > cleaning > (https://gerrit.ovirt.org/#/c/41810/).
The overhead comes from having to scan through every single object that we are transferring to the front end, even though right now only one or two object types have this particular problem. The scanning only happens if we actually transfer the object to the frontend. If there was a way to determine if we need to scan the objects being returned to the front end that would cut down on the overhead. Another question to ask, is the overhead BAD enough to care? I honestly don't know without doing some profiling. But my gut is telling me no it is not.
I agree this is the correct fix on the correct place. On the other hand, it needs some optimizations and tests if it actually works and if it is not a big bottleneck. Also we need to consider if we want to have some annotation on classes we want to filter before sending back to frontend or we want this to be done all the time.
Long story short, I think the patch which broke the frontend debugging should be reverted and merged once the https://gerrit.ovirt.org/#/c/41810/ is finished and tested.
What's the ETA on finishing https://gerrit.ovirt.org/#/c/41810 ?
I will be working on 41810 to make sure it is solid and is working as expected. I am expecting it to take 1-2 days to fully complete, but I will try to do it asap.
OK, Alexander have posted a new version of https://gerrit.ovirt.org/#/c/41810 and I think it is now good enough to be merged. I have tested it on my setup and everything seems to be working again.
I think there is some room for enhancements but that enhancements can be discussed separately in a separate patch.
Long story short - everyone who was stuck can now debug the FE again :) Thanx Alexander for the patch!
Thank you both for the quick analysis and the solution!
@Liran: could you please revert your patch? Because currently the FE debugging is pretty much broken (and I don't trust the web mode either...) and the solution is not completely clear now.
Let's see what the ETA is, as perhaps we can merge something soon. Liran's patch is a big change in all DB layers, so won't be easy to revert.
> > I'll leave the technical details to the UX experts here to see > > what's > > the > > right approach to do it in the frontend side. > > > > Thanks, > > Oved > > > > ----- Original Message ----- > > > > > From: "Alexander Wels" <awels@redhat.com> > > > To: "Martin Perina" <mperina@redhat.com> > > > Cc: "Liran Zelkha" <lzelkha@redhat.com>, devel@ovirt.org > > > Sent: Tuesday, June 2, 2015 4:16:31 AM > > > Subject: Re: [ovirt-devel] hibernate's internal PersistentBag > > > sent > > > to > > > FE > > > > > > On Monday, June 01, 2015 10:51:28 AM Martin Perina wrote: > > > > ----- Original Message ----- > > > > > > > > > From: "Alexander Wels" <awels@redhat.com> > > > > > To: "Tomas Jelinek" <tjelinek@redhat.com> > > > > > Cc: "Liran Zelkha" <lzelkha@redhat.com>, devel@ovirt.org > > > > > Sent: Monday, June 1, 2015 4:19:47 PM > > > > > Subject: Re: [ovirt-devel] hibernate's internal > > > > > PersistentBag > > > > > sent > > > > > to > > > > > FE > > > > > > > > > > On Monday, June 01, 2015 09:33:07 AM Tomas Jelinek wrote: > > > > > > ----- Original Message ----- > > > > > > > > > > > > > From: "Alexander Wels" <awels@redhat.com> > > > > > > > To: devel@ovirt.org > > > > > > > Cc: "Tomas Jelinek" <tjelinek@redhat.com>, "Liran > > > > > > > Zelkha" > > > > > > > <lzelkha@redhat.com> Sent: Monday, June 1, 2015 > > > > > > > 3:16:34 > > > > > > > PM > > > > > > > Subject: Re: [ovirt-devel] hibernate's internal > > > > > > > PersistentBag > > > > > > > sent > > > > > > > to > > > > > > > FE > > > > > > > > > > > > > > On Monday, June 01, 2015 09:08:50 AM Tomas Jelinek wrote: > > > > > > > > Hey all, > > > > > > > > > > > > > > > > since the > > > > > > > > org.ovirt.engine.core.common.job.Job/Step... > > > > > > > > has > > > > > > > > been > > > > > > > > moved > > > > > > > > to > > > > > > > > use > > > > > > > > the JPA we have a problem on frontend. The problem > > > > > > > > is > > > > > > > > that > > > > > > > > the > > > > > > > > @OneToMany > > > > > > > > annotations results in a List which is of type > > > > > > > > PersistentBag. > > > > > > > > When > > > > > > > > we > > > > > > > > send > > > > > > > > this to Frontend it fails during deserialization. > > > > > > > > It > > > > > > > > actually > > > > > > > > fails > > > > > > > > quite > > > > > > > > bad because the FE already has an ui-override of it > > > > > > > > which > > > > > > > > is > > > > > > > > not > > > > > > > > correct > > > > > > > > resulting in a ton of NPEs in development mode. > > > > > > > > > > > > > > > > So, there are 2 nasty fixes I have made where none > > > > > > > > of > > > > > > > > them > > > > > > > > should > > > > > > > > be > > > > > > > > merged > > > > > > > > but demonstrate the possibilities: 1: extend the FE > > > > > > > > to > > > > > > > > be > > > > > > > > able > > > > > > > > to > > > > > > > > work > > > > > > > > with > > > > > > > > the PersistentBag > > > > > > > > (https://gerrit.ovirt.org/#/c/41682/) > > > > > > > > not > > > > > > > > really > > > > > > > > good > > > > > > > > solution since the PersistenBag is an internal > > > > > > > > Hibernate > > > > > > > > class > > > > > > > > which > > > > > > > > is > > > > > > > > really not meant to be passed around > > > > > > > > > > > > > > > > 2: fix on the backend to not send the PersistentBag > > > > > > > > but > > > > > > > > an > > > > > > > > ArrayList. > > > > > > > > This > > > > > > > > is only a PoC fixed on a command we face the > > > > > > > > problem > > > > > > > > (https://gerrit.ovirt.org/#/c/41797/) Obviously > > > > > > > > this > > > > > > > > is > > > > > > > > not > > > > > > > > going > > > > > > > > to > > > > > > > > work > > > > > > > > for other commands accessing the same Job nor for > > > > > > > > other > > > > > > > > entities. > > > > > > > > > > > > > > > > So, the first option is generic but very very bad. > > > > > > > > The > > > > > > > > second > > > > > > > > option > > > > > > > > should > > > > > > > > be used but not sure how to do this in a cheep way > > > > > > > > (e.g. > > > > > > > > without > > > > > > > > using > > > > > > > > reflection to deep traverse everything sent back to > > > > > > > > frontend > > > > > > > > checking > > > > > > > > if > > > > > > > > it > > > > > > > > does not have a PersistentBag in it. > > > > > > > > > > > > > > Tomas, > > > > > > > > > > > > > > Thanks, I was investigating the same issue, I noticed > > > > > > > it > > > > > > > last > > > > > > > Friday > > > > > > > just > > > > > > > before leaving, so I was investigating the problem to > > > > > > > see > > > > > > > what > > > > > > > was > > > > > > > going > > > > > > > on. You are right we should not be sending > > > > > > > PersistentBag > > > > > > > to > > > > > > > the > > > > > > > frontend > > > > > > > at all. So how about we do a combination of [1] and > > > > > > > [2], > > > > > > > but > > > > > > > instead > > > > > > > of > > > > > > > delegating in [1] we actually simple throw an > > > > > > > exception > > > > > > > stating > > > > > > > don't > > > > > > > sent PersistentBag to the front end. that way anyone > > > > > > > inadvertently > > > > > > > using > > > > > > > it will be notified immediately (since their code > > > > > > > won't > > > > > > > work). > > > > > > > > > > > > Throwing the exception would help us in debugging but > > > > > > the > > > > > > main > > > > > > question > > > > > > is > > > > > > how will we make it work? Since we are planning to move > > > > > > more > > > > > > and > > > > > > more > > > > > > to > > > > > > JPA so we will face this issue more and more often. > > > > > > Solving > > > > > > it > > > > > > one > > > > > > by > > > > > > one > > > > > > on backend in each command is not going to work. > > > > > > > > > > How about something like this [1]? It appears to use some > > > > > aspects > > > > > to > > > > > translate > > > > > the hibernate internal classes into normal java util > > > > > classes. > > > > > > > > > > [1] https://code.google.com/p/dehibernator/ > > > > > > > > Well, not sure about that from performance point of view. > > > > > > > > If we really move away from GWT completely in 4.0, then > > > > implementing > > > > all > > > > hibernate inner collections in "uioverride" in a similar > > > > way > > > > as > > > > Tomas > > > > did > > > > seems to me as the best solution from performance and > > > > "easiest > > > > to > > > > remove > > > > when not needed" point of view. > > > > > > I took some inspiration from that code and wrote my own > > > fairly > > > simple > > > hibernate persistent collection replacer, and I put the patch > > > up > > > here > > > [3]. > > > It > > > still uses reflection so it is probably not the fastest thing > > > ever > > > written. > > > > > > [3] https://gerrit.ovirt.org/#/c/41810/ > > > > > > > > > > Alexander > > > > > > > > > > > > > > > Any better ideas? > > > > > > > > Thanx, > > > > > > > > Tomas > > > > > > > > _______________________________________________ > > > > > > > > Devel mailing list > > > > > > > > Devel@ovirt.org > > > > > > > > http://lists.ovirt.org/mailman/listinfo/devel > > > > > > > > > > _______________________________________________ > > > > > Devel mailing list > > > > > Devel@ovirt.org > > > > > http://lists.ovirt.org/mailman/listinfo/devel > > > > > > _______________________________________________ > > > Devel mailing list > > > Devel@ovirt.org > > > http://lists.ovirt.org/mailman/listinfo/devel > > > > _______________________________________________ > > Devel mailing list > > Devel@ovirt.org > > http://lists.ovirt.org/mailman/listinfo/devel
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