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From Alexey Goncharuk <alexey.goncha...@gmail.com>
Subject Re: Set default cache synchronization mode to FULL_SYNC
Date Wed, 02 Aug 2017 08:11:04 GMT
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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