2:59 a.m.
----- Original Message -----
From: "Oved Ourfali" <ovedo(a)redhat.com>
To: awels(a)redhat.com
Cc: "Liran Zelkha" <lzelkha(a)redhat.com>, devel(a)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.
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/).
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(a)redhat.com>
> To: "Martin Perina" <mperina(a)redhat.com>
> Cc: "Liran Zelkha" <lzelkha(a)redhat.com>, devel(a)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(a)redhat.com>
> > > To: "Tomas Jelinek" <tjelinek(a)redhat.com>
> > > Cc: "Liran Zelkha" <lzelkha(a)redhat.com>, devel(a)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(a)redhat.com>
> > > > > To: devel(a)ovirt.org
> > > > > Cc: "Tomas Jelinek" <tjelinek(a)redhat.com>,
"Liran Zelkha"
> > > > > <lzelkha(a)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
> > > > > > _______________________________________________
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