[infinispan-dev] CacheEntry vs. Metadata

[Radim Vansa]

Hi,

I was already several times looking on the class hierarchy of CacheEntry 
and its descendants. Since the documentation of those interfaces is 
usually a one liner, I'd like to ask for the big picture:

So we have CacheEntry, which implements MetadataAware - therefore, it 
contains a metadata, which define lifespan, maxIdle time and version. 
However, even the CacheEntry interface itself contains getters for 
lifespan and idle time and MortalCacheEntry hosts the fields - so I see 
that there's some duplication with the Metadata object.
Beyond the expiration-related stuff (and common key - value getters), 
CacheEntry has several methods querying and manipulating its state - 
isChanged, isValid, isRemoved etc. It's a bit confusing that this is 
presented not as a single state but rather a matrix of boolean states. 
When I've tried to implement EntryProcessor several weeks ago (I've 
stopped the attempts since this should be implemented in Infinispan 8), 
I had quite a hard time figuring out which should be set and how in case 
I want to update/remove the entry. undelete() and skipLookup() are not 
obvious, either.

Is the reason for having Immortal/Mortal/Transient/TransientMortal 
entries + Metadata* versions + *Values to optimally use memory?

Then there are the ReadCommitted and RepeatableRead entries - are these 
ever stored in data container, or just in context? What's the exact 
relation between those implementing InternalCacheEntry and MVCCEntry?

Then there's the DeltaAwareCacheEntry - this does not fit to the image 
for me at all.

I am also not sure about the relation of EmbeddedMetadata and 
InternalMetadataImpl

Thanks for your insight!

Radim


-- 
Radim Vansa <rvansa at redhat.com>
JBoss Performance Team