[xwiki-devs] XWikiDocuments not thread safe added to XWikiCacheStore

Hi devs http://jira.xwiki.org/browse/XWIKI-13623 I would like to discuss the suggested solution, before I start implementing it: *I suggest the following solution:* Introducing a nested DocumentLoader class which loads the document calling the basestore loadXWikiDoc in a synchronized getDocOrLoad method. The DocumentLoader objects gets instantiated in the cacheStore on a cache miss. It then gets stored in a ConcurrentHashMap using the same key which is used for the document cache (DocumentReference including language). Using putIfAbsent to insert the DocumentLoader and calling the synchronized load method on the object in the map solves the memory visibility issue and moreover ensures that the same XWikiDocument is not loaded multiple times concurrently from the database. It is still possible to load different documents in parallel. A DocumentLoader will load the XWikiDocument only once and the returns the identical document object on any following call of the synchronized getDocOrLoad method. WDYT? Kind Regards, Fabian