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

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