[infinispan-dev] Caches need be stopped in a specific order to respect cross-cache dependencies

[Sanne Grinovero]

The goal being to resolve ISPN-4561, I was thinking to expose a very
simple reference counter in the AdvancedCache API.

As you know the Query module - which triggers on indexed caches - can
use the Infinispan Lucene Directory to store its indexes in a
(different) Cache.
When the CacheManager is stopped, if the index storage caches are
stopped first, then the indexed cache is stopped, this might need to
flush/close some pending state on the index and this results in an
illegal operation as the storate is shut down already.

We could either implement a complex dependency graph, or add a method like:


  boolean incRef();

on AdvancedCache.

when the Cache#close() method is invoked, this will do an internal
decrement, and only when hitting zero it will really close the cache.

A CacheManager shutdown will loop through all caches, and invoke
close() on all of them; the close() method should return something so
that the CacheManager shutdown loop understand if it really did close
all caches or if not, in which case it will loop again through all
caches, and loops until all cache instances are really closed.
The return type of "close()" doesn't necessarily need to be exposed on
public API, it could be an internal only variant.

Could we do this?

--Sanne