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From Vladimir Ozerov <voze...@gridgain.com>
Subject Re: Set default cache synchronization mode to FULL_SYNC
Date Wed, 02 Aug 2017 08:27:17 GMT
+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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