[infinispan-dev] FlagAffectedCommand interface hierarchy (ISPN-761)

[Galder Zamarreño]

On May 31, 2013, at 4:11 PM, Sanne Grinovero <sanne at infinispan.org> wrote:

> On 31 May 2013 14:37, William Burns <wburns at redhat.com> wrote:
>> While adding changes for cache methods (entrySet, keySet, values, size) to include passivated entries it had been pointed out to conditionally do these operations if flags such as SKIP_CACHE_STORE and SKIP_CACHE_LOAD were provided.  Also does anyone have any feedback on if both flags should apply or just say SKIP_CACHE_STORE?
> 
> Right, that could definitely be improved. I would expect both to be
> needed as one mentions "store", the other "load", but in practice it
> seems that SKIP_CACHE_STORE skips both operations. I think this should
> at least be clarified in the javadocs.
> 
>> Currently SizeCommand, EntrySetCommand, ValuesCommand and KeySetCommand do not inherit from FlagAffectedCommand which are used for commands that behavior is dependent upon flags.
> 
> You just listed the most evil operations you can use in Infinispan.
> All of these are inherently broken as we need to constantly clarify to
> users that they only apply to the local datastore, which makes it even
> trickier to test something on a single node and then expect it to work
> on multiple nodes as well..

… which is why they're not included in JCache/JSR-107. All you have there is an iterator()...

> I know, we have warnings on javadoc but since it implements
> ConcurrentMap and Map, these warnings are easily overseen.
> 
> So my doubt actually is, since these operations are fundamentally
> unreliable, why should they include CacheStore s as well? IMHO they
> should all throw a runtime exception to flag they are not supported.
> I guess we don't throw such exceptions as they could be useful for
> some metrics, but still I think it would be more appropriate to move
> this responsibility to a statistics/monitoring API.

Indeed, they should be removed at some point and align ourselves closer to JCache on this occasion. +1 on being something about statistics/monitoring, which is done at the local level (tools can be used to aggregate results, or even map/reduce?)

> 
> Sanne
> 
> 
>> The problem is that FlagAffectedCommand currently extends VisitableCommand, TopologyAffectedCommand, MetadataAwareCommand interfaces.  These interfaces do not really apply to the commands I am working on as they are local only.  I was planning on removing the extended interfaces from the FlagAffectedCommand interface and update all the commands that implement this interface currently to make sure they still properly implement the additional interfaces.  Searching for instanceof FlagAffectedCommand it also appears that all current references should be alright after refactoring.  Once these interfaces are decoupled I can add the FlagAffectedCommand interface to the SizeCommand, EntrySetCommand, ValuesCommand and KeySetCommand and subsequently to the CommandFactory and my changes should be good.
>> 
>> Any opinions or concerns?
>> 
>> Thanks,
>> 
>> - Will
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> 
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--
Galder Zamarreño
galder at redhat.com
twitter.com/galderz

Project Lead, Escalante
http://escalante.io

Engineer, Infinispan
http://infinispan.org