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From Anton Vinogradov <avinogra...@gridgain.com>
Subject Re: Set default cache synchronization mode to FULL_SYNC
Date Fri, 04 Aug 2017 10:23:02 GMT
+1 to change PRIMARY_SYNC to FULL_SYNC and keep readFromBackup=true

Dmitriy,
Why should we wait for 3.0?
This change looks safe for me.

On Wed, Aug 2, 2017 at 9:51 PM, Dmitriy Setrakyan <dsetrakyan@apache.org>
wrote:

> We have to wait with any default changes to 3.0, unfortunately.
>
> On Wed, Aug 2, 2017 at 8:30 PM, Vladimir Ozerov <vozerov@gridgain.com>
> wrote:
>
> > Not sure about readFromBackup, but changing PRIMARY_SYNC to FULL_SYNC
> looks
> > safe to me. Any other thoughts?
> >
> > ср, 2 авг. 2017 г. в 21:10, Denis Magda <dmagda@apache.org>:
> >
> > > +1 for both suggestions but I’m not sure we can do the change till 3.0.
> > >
> > > —
> > > Denis
> > >
> > > > On Aug 2, 2017, at 1:27 AM, Vladimir Ozerov <vozerov@gridgain.com>
> > > wrote:
> > > >
> > > > +1 for readFromBackup=false as well :-) Another example of default
> > value
> > > > with subtle effects.
> > > >
> > > > On Wed, Aug 2, 2017 at 11:11 AM, Alexey Goncharuk <
> > > > alexey.goncharuk@gmail.com> wrote:
> > > >
> > > >> Vladimir,
> > > >>
> > > >> Personally, I agree that we should put correctness over performance,
> > > >> however (1) is not a correct statement for TRANSACTIONAL caches. A
> > > >> transactional client always validates the result of an operation and
> > > throw
> > > >> a correct exception if operation failed. (1) is true for ATOMIC
> > caches,
> > > >> though.
> > > >>
> > > >> A user can get in trouble in this default for both TX and ATOMIC
> > caches
> > > if
> > > >> a put is performed from a backup node and readFromBackup is set to
> > > false.
> > > >> In this case, the simple read-after-write scenario may fail. I would
> > > rather
> > > >> set readFromBackup to false by default, however, this fixes neither
> > the
> > > SQL
> > > >> nor ATOMIC caches issues.
> > > >>
> > > >> +1 for the change, and extend the warning for partitioned caches
> with
> > > >> readFromBackup=true and PRIMARY_SYNC.
> > > >>
> > > >>
> > > >>
> > > >> 2017-08-02 10:58 GMT+03:00 Vladimir Ozerov <vozerov@gridgain.com>:
> > > >>
> > > >>> Igniters,
> > > >>>
> > > >>> I want to re-iterate idea of changing default synchronization
mode
> > from
> > > >>> PRIMARY_SYNC to FULL_SYNC.
> > > >>>
> > > >>> Motivation:
> > > >>> 1) If user set [cacheMode=PARTITIONED, backups=1] he still could
> > loose
> > > >> data
> > > >>> silently. Because primary node could report success to the client
> and
> > > >> then
> > > >>> crash before data is propagated to backups.
> > > >>> 2) If user set [cacheMode=REPLICATED] and use SQL, he will might
> get
> > > >>> invalid results if cache is being updated concurrently - well
known
> > > >> issue.
> > > >>>
> > > >>> The only advantage of PRIMARY_SYNC is slightly better performance,
> > but
> > > we
> > > >>> should prefer correctness over performance.
> > > >>>
> > > >>> Proposed changes:
> > > >>> 1) Make FULL_SYNC default;
> > > >>> 2) Print a warning about possibly incorrect SQL results if
> REPLICATED
> > > >> cache
> > > >>> is started in PRIMARY_SYNC mode.
> > > >>>
> > > >>> Thoughts?
> > > >>>
> > > >>> Vladimir.
> > > >>>
> > > >>
> > >
> > >
> >
>

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