[infinispan-dev] Default cache

[Paul Ferraro]

On Wed, Nov 30, 2016 at 9:13 AM, Tristan Tarrant <ttarrant at redhat.com> wrote:
> Some additional notes:
>
> - currently the XSD specifies the default-cache attribute on the
> cache-container element as required, but the parser doesn't enforce it.
> - A default ConfigurationBuilder is created for the default cache if one
> has not been specified
>
> My questions:
>
> 1. do we want the default cache to be optional or actually require it in
> the declarative configuration ?

In WildFly, default-cache has been optional since WF8.  The
cache-container used for hibernate 2LC, for example, does not have any
concept of a default-cache.  So, for us anyway, it makes sense for
default-cache to be optional.  However, we have the luxury of falling
back to Infinispan's default getCache() logic in the event that no
default-cache was specified.

> ** A: no enforcement. In this case requesting the default cache should
> print a warning about falling back to a "default" empty configuration.
>
> ** B: we don't require the user to specify a default cache in the
> configuration, but invoking getCache() will throw an exception.
>
> ** C: enforce it, although this will break all those XML files who
> haven't specified it.
>
> My preference is to use the namespace version and go for the A approach
> for < 9.0 and the B approach otherwise.

I think that makes sense.

> 2. currently, requesting a named cache for which a configuration hasn't
> been defined implicitly creates the cache by using the default
> configuration as a template.
>
> ** A: continue as is
>
> ** B: continue to implicitly create a cache, but use an empty
> configuration instead of using the default configuration, as this has
> been the source of confusion among users. Also print a warning.
>
> ** C: do not create caches unless a configuration has been explicitly
> provided.
>
> My preference is to use the namespace version and go for the A approach
> for < 9.0 and the C approach otherwise.

Agreed.

> Unfortunately the namespace version trick doesn't work for programmatic
> configurations. Probably we should add a boolean flag on the
> GlobalConfigurationManager (e.g. implicitCacheCreation) which defaults
> to false (because that's the "new order") but allows switching to the
> old behaviour if needed.
>
> In any case I'd like to also introduce a JCache-like createCache() API

I think it would be best/cleanest if caches created via this API are
anonymous (i.e. not managed by the cache manager or made accessible
via getCache(String)).  That way there is no ambiguity about who is
meant to manage the lifecycle (user vs container).

> Tristan
>
> On 10/11/16 13:20, Paul Ferraro wrote:
>> +1000
>>
>> This is precisely how we've setup cache manager semantics in WildFly
>> (since AS7):
>> https://github.com/wildfly/wildfly/blob/master/clustering/infinispan/spi/src/main/java/org/wildfly/clustering/infinispan/spi/CacheContainer.java
>> https://github.com/wildfly/wildfly/blob/master/clustering/infinispan/extension/src/main/java/org/jboss/as/clustering/infinispan/DefaultCacheContainer.java
>>
>> I'd love to be able to drop this.
>>
>> Paul
>>
>> On Thu, Nov 10, 2016 at 3:38 AM, Tristan Tarrant <ttarrant at redhat.com> wrote:
>>> In the discussion for [1] the subject of the default cache and the way
>>> it affects configuration inheritance came up.
>>>
>>> My proposal is:
>>> - remove the default cache as a special cache altogether
>>> - CacheManager.getCache()  should return the named cache specified as
>>> default in the configuration.
>>> - the programmatic GlobalConfigurationBuilder/GlobalConfiguration should
>>> have the notion of the default named cache (currently this is handled in
>>> the parser)
>>> - Retrieving the cache named "___defaultcache" should actually retrieve
>>> the above named cache
>>>
>>> Opinions ?
>>>
>>> Tristan
>>>
>>> [1] https://github.com/infinispan/infinispan/pull/4631
>>> --
>>> Tristan Tarrant
>>> Infinispan Lead
>>> JBoss, a division of Red Hat
>>> _______________________________________________
>>> infinispan-dev mailing list
>>> infinispan-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
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>
> --
> Tristan Tarrant
> Infinispan Lead
> JBoss, a division of Red Hat
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