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From Alexei Scherbakov <alexey.scherbak...@gmail.com>
Subject Re: Getting rid of NONE cache rebalance mode
Date Wed, 22 Jul 2020 07:00:19 GMT
As a reminder - we already have a ticket for a deprecation of
rebalanceDelay as well [1]

[1] https://issues.apache.org/jira/browse/IGNITE-12662

ср, 22 июл. 2020 г. в 09:39, Alexei Scherbakov <alexey.scherbakoff@gmail.com
>:

> Ivan,
> My opinion the ASYNC rebalancing is a best approach for off-loading 3-d
> party store, and it provides consistency.
>
> +1 for deprecation of NONE in the next release - ignore NONE and use ASYNC
> instead
> For those who require absence of rebalancing for some reason still be
> possible to use rebalanceDelay=infinity.
>
> +1 for removal of rebalanceMode in 3.0.
> Note what we still require SYNC logic internally for system cache in some
> places.
>
>
>
> вт, 21 июл. 2020 г. в 15:59, Ivan Pavlukhin <vololo100@gmail.com>:
>
>> Alexey,
>>
>> Thank you for explanation. I feel that I miss a couple bits to
>> understand the picture fully. I am thinking about a case which I tend
>> to call a Memcached use-case. There is a cache over underlying storage
>> with read-through and expiration and without any rebalancing at all.
>> When new nodes enter they take ownership for some partitions from
>> already running nodes and serve client requests. Entries for not
>> owning anymore partitions expire according to configuration.
>>
>> Actually, I have an idea. My guess is that "rebalancing" is a smarter
>> and better approach than waiting for expiration. Am I right?
>>
>> 2020-07-21 15:31 GMT+03:00, Alexey Goncharuk <alexey.goncharuk@gmail.com
>> >:
>> > 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
>> >> >
>> >>
>> >
>>
>>
>> --
>>
>> Best regards,
>> Ivan Pavlukhin
>>
>
>
> --
>
> Best regards,
> Alexei Scherbakov
>


-- 

Best regards,
Alexei Scherbakov

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