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From Denis Magda <dma...@gridgain.com>
Subject Re: Cache inserts in full offheap
Date Fri, 05 Feb 2016 13:51:30 GMT
Eviction of entries doesn't trigger flushing of data from the 
write-behind store [1] to your disk storage.
The write-behind store flushes data basing on flush frequency and its 
internal queue size.

Actually, when you put an entry its copy will be stored in offheap and 
in the write-behind store internal queue.
When an entry is evicted from the offheap cache it's not completely lost 
in your case because either write-behind store's queue or your disk 
storage already has it.

You don't see any file on your disk because the write-behind store's 
queue size is enough to hold all the entries. When you get an entry that 
is already evicted it's taken from the write-behind queue, placed back 
to memory and returned to your application.

If you remove this from your configuration
fccfg.setReadThrough(true);

then you will see that some entries are already evicted because you will 
get 'null' instead of their real values.

Write-behind queue size can be controlled with 'setFlushSize' parameter.

[1] 
https://github.com/apache/ignite/blob/b3d347e35a254928fd1c4a0473f1b17d642c72f3/modules/core/src/main/java/org/apache/ignite/internal/processors/cache/store/GridCacheWriteBehindStore.java

--
Denis

On 2/5/2016 4:01 PM, bsmets wrote:
> Hi,
>
> We don't use any Near caches. You can find our configuration on this gist:
> https://gist.github.com/anonymous/ebfa88893764f8a3a5f8
>
> Note that we know that these settings are ridiculous for any serious
> production environment but we are just interested in what happens when the
> offheap gets filled up. We would expect to see the entries that are being
> evicted to be written to disk (bypassing the writebehind settings) so they
> don't get lost when they get evicted as they have no where else to go (swap
> disabled). However, we observed that no files are getting written to disk,
> the cache contains only the last X offheap entries with others evicted BUT
> all entries are still accessible and can be retrieved just fine. Maybe this
> is just a weird case of luck with memory not being cleared yet? (Although
> this experiment is repeatable with the same result every time..)
>
>
>
> --
> View this message in context: http://apache-ignite-users.70518.x6.nabble.com/Cache-inserts-in-full-offheap-tp2851p2858.html
> Sent from the Apache Ignite Users mailing list archive at Nabble.com.


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