[infinispan-dev] Fwd: CloudCacheStore Bug

[Philippe Van Dyck]

>
> Am I missing something ? Loosing data is something I cannot afford ! I Plan
> to use this store as a *permanent* one... I have no backup ! (Actually S3 is
> the backup) - So, no, I don't want this ... at any price ;-)
>
>
> Then set <async enabled="false" /> in your cache store config.  :-)
>

That is exactly what I planned to do... for the FileCacheStore since the
latency is quite low and the failure rate almost zero.
But the S3 store is very slow, and asynchronism is not a luxury...

Right now, I am trying to make my own custom solution based on the size of
the cache in memory (as trigger) and then I will evict specific oldest
entries... hoping that async transactions are fully committed.


>
>
>
>> reduced by looking through the async queue as well, before checking the
>> underlying store.  But as I said, this just reduces the size of this window
>> and not eliminate it altogether, since this is async and there is no
>> guarantee that the cache store has finished writing internally (e.g., an
>> fsync() operation or in the case of S3, Amazon's eventual consistency
>> model).
>>
>>
>> Why should eviction be transactional?  I don't need eviction to be an
>> all-or-nothing, reversible event. :)  If an entry gets evicted, cool.  If
>> not (for whatever reason), too bad, move on to the next evictable entry.
>>
>
> You are right, we don't want to rollback evictions... but maybe we should
> use a priority queue to be sure that evictions are done after any other
> command ? Doesn't it solve it all ?
>
> 1) The eviction thread runs (we could lower the priority of this thread
> too)
> 2) It fills a queue of keys to evict
> 3) The async queue is prioritized and evicts entries ... when there is
> nothing else to do (suddenly it looks like garbage collecting)
>
>
> That is a possibility.  But I don't expect to be making any drastic changes
> to the existing eviction code anymore.  Don't know if you have been
> following discussions re: LIRS, lock amortization, etc., but Vladimir is
> working on some very interesting self-evicting, bounded data containers
> which would mean that the eviction threads, etc all get ripped out.
>
>
Sounds terrific...

Just to close the subject, shouldn't the documentation explicitly say that
async and eviction are not "compatible" ?

phil
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