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From Ivan Pavlukhin <vololo...@gmail.com>
Subject Re: Forbid mixed cache groups with both atomic and transactional caches
Date Fri, 07 Feb 2020 08:16:05 GMT
Nikolay, Ivan,

Thank you guys! I knew that I should not worry =)

Best regards,
Ivan Pavlukhin

ср, 5 февр. 2020 г. в 13:46, Ivan Rakov <ivan.glukos@gmail.com>:
>
> Ivan,
>
> Thanks for pointing this out. Less than one day is indeed too early to
> treat this discussion thread as a "community conclusion". Still, the
> consensus among the current participants made me feel that a conclusion
> will be reached.
> We'll surely get back to the discussion if opposite opinions will arise.
>
> On Wed, Feb 5, 2020 at 1:11 PM Ivan Pavlukhin <vololo100@gmail.com> wrote:
>
> > Folks,
> >
> > A bit of offtop. Do we have some recommendations in the community how
> > long should we wait until treating something as "a Community
> > conclusion"? It worries me a little bit that I see a discussion for a
> > first time and there is already a conclusion. And the discussion was
> > started lesser than 24 hours ago. I suppose we should allow everyone
> > interested to share an opinion (here I agree with the proposal) and it
> > usually requires some time in open-source communities.
> >
> > ср, 5 февр. 2020 г. в 10:58, Ivan Rakov <ivan.glukos@gmail.com>:
> > >
> > > Folks,
> > >
> > > Thanks for your feedback.
> > > I've created a JIRA issue on this change:
> > > https://issues.apache.org/jira/browse/IGNITE-12622
> > >
> > > On Tue, Feb 4, 2020 at 10:43 PM Denis Magda <dmagda@apache.org> wrote:
> > >
> > > > +1 from my end. It doesn't sound like a big deal if Ignite users need
> > to
> > > > define separate groups for atomic and transactional caches.
> > > >
> > > > -
> > > > Denis
> > > >
> > > >
> > > > On Tue, Feb 4, 2020 at 3:28 AM Ivan Rakov <ivan.glukos@gmail.com>
> > wrote:
> > > >
> > > > > Igniters,
> > > > >
> > > > > Apparently it's possible in Ignite to configure a cache group with
> > both
> > > > > ATOMIC and TRANSACTIONAL caches.
> > > > > Proof: IgniteCacheGroupsTest#testContinuousQueriesMultipleGroups*
> > tests.
> > > > > In my opinion, it would be better to remove such possibility from
the
> > > > > product. There are several reasons:
> > > > >
> > > > > 1) The original idea of grouping caches was optimizing storage
> > overhead
> > > > and
> > > > > PME time by joining data of similar caches into the same partitions.
> > > > ATOMIC
> > > > > and TRANSACTIONAL caches provide different guarantees and are
> > designed
> > > > for
> > > > > different use cases, thus they can hardly be called "similar".
> > > > >
> > > > > 2) Diving deeper: synchronization protocols and possible reasons
for
> > > > > primary-backup divergences are conceptually different for ATOMIC
and
> > > > > TRANSACTIONAL cases. In TRANSACTIONAL case, transactions recovery
> > > > protocol
> > > > > allows to recover consistency if any participating node will fail,
> > but
> > > > for
> > > > > ATOMIC caches there's possible scenario with failure of primary node
> > > > where
> > > > > neither of backups will contain the most recent state of the data.
> > > > Example:
> > > > > one backup have received updates 1, 3, 5 while another have received
> > 2, 4
> > > > > (which is possible due to message reordering), and even tracking
> > counters
> > > > > [1] won't restore the consistency. The problem is that we can't
> > > > distinguish
> > > > > what kind of conflict we have faced in case update counters have
> > diverged
> > > > > in a mixed group.
> > > > >
> > > > > 3) Mixed groups are poorly tested. I can't find any tests except
a
> > couple
> > > > > of smoke tests in IgniteCacheGroupsTest. We can't be sure that
> > different
> > > > > synchronization protocols will work correctly for such
> > configurations,
> > > > > especially under load and with a variety of dependent configuration
> > > > > parameters.
> > > > >
> > > > > 4) I have never heard of any feedback on mixed groups. I have asked
> > > > > different people on this and no one recalled any attempts to
> > configure
> > > > such
> > > > > groups. I believe that in fact no one has ever tried to do it.
> > > > >
> > > > > Please let me know if you are aware of any cases where mixed groups
> > are
> > > > > used or reasons to keep them. Otherwise I'll create a ticket to
> > prohibit
> > > > > mixed configurations.
> > > > >
> > > > > [1]: https://issues.apache.org/jira/browse/IGNITE-11797
> > > > >
> > > > > --
> > > > > Best Regards,
> > > > > Ivan Rakov
> > > > >
> > > >
> >
> >
> >
> > --
> > Best regards,
> > Ivan Pavlukhin
> >

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