[infinispan-dev] cache loader/preload

[Ray Tsang]

Btw how do we deal with preloading in a cluster?

Eg how do we prevent every node from preloading the same data?

On Aug 14, 2013, at 16:09, Mircea Markus <mmarkus at redhat.com> wrote:

>
> On 14 Aug 2013, at 20:53, Sanne Grinovero <sanne at infinispan.org> wrote:
>
>> On 14 August 2013 17:59, Mircea Markus <mmarkus at redhat.com> wrote:
>>>
>>> On 14 Aug 2013, at 15:26, Sanne Grinovero <sanne at infinispan.org> wrote:
>>>
>>>> On 14 August 2013 11:15, Mircea Markus <mmarkus at redhat.com> wrote:
>>>>> Currently the "preload" attribute is configured at *loaders* level and the first cache loader in the chain is used for preloading.
>>>>> A better place for preload might be the individual loader element: would indicate clearly which loader is used for preloading and also consistent with the fetchPeristentState which is again defined on a per loader basis.
>>>>>
>>>>> How does it sound?
>>>>
>>>> Very confusing actually :-)
>>>> Are you going to prevent me to enable "preload" on multiple Cache
>>>> Loaders elements?
>>>
>>> I'm not going to take anything from you, this is something you're not allowed to do ATM :-)
>>
>> That's exactly my point. I'm not allowed to do it ATM, but if you
>> change the position of this attribute to *each* loader it will look
>> like I could enable/disable it differently on a per-instance.
>
> Gotcha, I'll either add a check to allow specifying preload on a single store, or (if time allows) I'll implement the multiple preload feature.
>
>>
>>>
>>>> And what if I'm actually storing entries in
>>>> different CacheStore instanced based on some discriminator, like the
>>>> value (key) type?
>>>>
>>>> To make a practical example, the Lucene Directory CacheLoader only
>>>> loads some specific types, and only from named indexes which match a
>>>> configured name. You could want multiple instances using different
>>>> configurations, so that for each index name stored in the same cache
>>>> you actually store them in different cachestores.
>>>>
>>>> Similar situation, with the JPA CacheStore you might want to use
>>>> multiple independent instances, one per mapped type. Not necessarily
>>>> needed (one could improve the CacheStore implementation as well) but
>>>> it gives lot of flexibility, like connecting to different RDBMs
>>>> instances or with different credentials/schemas, etc...
>>>
>>> Indeed user might want this in the future. Moving "preload" at "loader" level would only facilitate that.
>>
>> Right. I'm making those examples to highlight the benefit of moving
>> the attribute to each cachestore, as you proposed, but this only makes
>> sense if you actually allow the option to be applied differently for
>> each instance.
>
> Cheers,
> --
> Mircea Markus
> Infinispan lead (www.infinispan.org)
>
>
>
>
>
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