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From Dmitriy Setrakyan <dsetrak...@apache.org>
Subject Re: MVCC configuration
Date Wed, 20 Sep 2017 04:30:08 GMT
Can caches within the same group have different MVCC configuration?

On Tue, Sep 19, 2017 at 2:34 AM, Vladimir Ozerov <vozerov@gridgain.com>
wrote:

> What I mean is that it might be not applicable for DML by design. E.g. may
> be we will have to fallback to per-memory-policy approach, or to
> per-cache-group. As we do not know it at the moment and there is no clear
> demand from users, I would simply put it aside to avoid in mess in public
> API in future.
>
> Moreover, per-cache flag raises additional questions which can be put out
> of scope otherwise. E.g. is it legal to mix MVCC and non-MVCC caches in a
> single transaction? If yes, what is the contract? Without fine-grained
> per-cache approach in the first iteration we can avoid answering it.
>
> On Tue, Sep 19, 2017 at 12:25 PM, Semyon Boikov <sboikov@gridgain.com>
> wrote:
>
> > If it is not valid for DML then we can easily detect this situation and
> > throw exception, but if I do not use DML why non make it configurable
> > per-cache?
> >
> > On Tue, Sep 19, 2017 at 12:22 PM, Vladimir Ozerov <vozerov@gridgain.com>
> > wrote:
> >
> > > I would say that per-cache configuration should be out of scope as well
> > for
> > > the first iteration. Because we do not know whether it will be valid
> for
> > > DML.
> > >
> > > On Tue, Sep 19, 2017 at 12:15 PM, Semyon Boikov <sboikov@gridgain.com>
> > > wrote:
> > >
> > > > Folks, thank you for feedback, I want to summarize some decisions:
> > > >
> > > > 1. Mvcc is disabled by default. We'll add two flags to enable mvcc:
> > > > per-cache flag - CacheConfiguration.isMvccEnabled, default value for
> > all
> > > > caches - IgniteConfiguration.isMvccEnabled.
> > > > 2. For initial implementation mvcc for ATOMIC cache is out of scope,
> it
> > > can
> > > > be enabled only for TRANSACTIONAL caches.
> > > > 3. Mvcc coordinator can be any server node (oldest server node is
> > > selected
> > > > automatically). Also I believe we need possibility to have
> *dedicated*
> > > mvcc
> > > > coordinator nodes which will process only internal mvcc messages.
> Node
> > > can
> > > > be marked as dedicated coordinator via new flag
> > > > IgniteConfiguration.isMvccCoordinator or we can add separate
> > > > MvccConfiguration bean. But let's skip this decision for now before
> we
> > > have
> > > > benchmarks numbers.
> > > > 4. Need add some metrics to monitor mvcc coordinator performance.
> > > >
> > > >
> > > > Thanks
> > > >
> > > > On Tue, Sep 19, 2017 at 10:47 AM, Vladimir Ozerov <
> > vozerov@gridgain.com>
> > > > wrote:
> > > >
> > > > > This could be something like "preferredMvccCoordinator".
> > > > >
> > > > > On Tue, Sep 19, 2017 at 10:40 AM, Alexey Goncharuk <
> > > > > alexey.goncharuk@gmail.com> wrote:
> > > > >
> > > > > > >
> > > > > > > I agree that we need coordinator nodes, but I do not understand
> > why
> > > > > can't
> > > > > > > we reuse some cache nodes for it? Why do we need to ask
user to
> > > start
> > > > > up
> > > > > > > yet another type of node?
> > > > > > >
> > > > > >
> > > > > > Dmitriy,
> > > > > >
> > > > > > My understanding is that Semyon does not deny a cache node to
be
> > used
> > > > as
> > > > > a
> > > > > > coordinator. This property will allow to optionally have a
> > > *dedicated*
> > > > > node
> > > > > > serving as a coordinator to improve cluster throughput under
> heavy
> > > > load.
> > > > > >
> > > > >
> > > >
> > >
> >
>

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