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From Alexey Goncharuk <alexey.goncha...@gmail.com>
Subject Re: Getting rid of NONE cache rebalance mode
Date Tue, 21 Jul 2020 12:31:37 GMT
Ivan,

In my understanding this mode does not work at all even in the presence of
ForceKeysRequest which is now supposed to fetch values from peers in case
of a miss. In this mode we 1) move partitions to OWNING state
unconditionally, and 2) choose an arbitrary OWNING node for force keys
request. Therefore, after a user started two additional nodes in a cluster,
the request may be mapped to a node which does not hold any data. We will
do a read-through in this case, but it will result in significant load
increase on a third-party storage right after a node started, which means
that adding a node will increase, not decrease, the load on the database
being cached.
All these issues go away when (A)SYNC mode is used.

Val,
The idea makes sense to me - a user can use rebalance future to wait for
rebalance to finish. This will simplify the configuration even further.

пн, 20 июл. 2020 г. в 21:27, Valentin Kulichenko <
valentin.kulichenko@gmail.com>:

> +1 for deprecating/removing NONE mode.
>
> Alexey, what do you think about the SYNC mode? In my experience, it does
> not add much value as well. I would go as far as removing the
> rebalancingMode parameter altogether (probably in 3.0).
>
> -Val
>
> On Mon, Jul 20, 2020 at 11:09 AM Ivan Pavlukhin <vololo100@gmail.com>
> wrote:
>
> > Alexey, Igniters,
> >
> > Could you please outline motivation answering following questions?
> > 1. Does this mode generally work correctly today?
> > 2. Can this mode be useful at all?
> >
> > I can imagine that it might be useful in a transparent caching use
> > case (if I did not misunderstand).
> >
> > 2020-07-20 20:39 GMT+03:00, Pavel Tupitsyn <ptupitsyn@apache.org>:
> > > +1
> > >
> > > More evidence:
> > >
> >
> https://stackoverflow.com/questions/62902640/apache-ignite-cacherebalancemode-is-not-respected-by-nodes
> > >
> > > On Mon, Jul 20, 2020 at 8:26 PM Alexey Goncharuk
> > > <alexey.goncharuk@gmail.com>
> > > wrote:
> > >
> > >> Igniters,
> > >>
> > >> I would like to run the idea of deprecating and probably ignoring the
> > >> NONE
> > >> rebalance mode by the community. It's in the removal list for Ignite
> 3.0
> > >> [1], but it looks like it still confuses and creates issues for users
> > >> [2].
> > >>
> > >> What about deprecating it in one of the next releases and even
> ignoring
> > >> this constant in further releases, interpreting it as ASYNC, before
> > >> Ignite
> > >> 3.0? I find it hard to believe that any Ignite user actually has
> > >> RebalanceMode.NONE set in their configuration due to its absolutely
> > >> unpredictable behavior.
> > >>
> > >> Thanks for your thoughts,
> > >> --AG
> > >>
> > >> [1]
> > >>
> > >>
> >
> https://cwiki.apache.org/confluence/display/IGNITE/Apache+Ignite+3.0+Wishlist
> > >> [2]
> > >>
> > >>
> >
> http://apache-ignite-developers.2346864.n4.nabble.com/About-Rebalance-Mode-SYNC-amp-NONE-td47279.html
> > >>
> > >
> >
> >
> > --
> >
> > Best regards,
> > Ivan Pavlukhin
> >
>

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