As discussed on IRC, the idea is to make IndexManager and BackendQueueProcessor two independent, orthogonal aspects:

• IM concerns how index changes are applied to a certain indexing technology (Lucene, ES)
• BQP concerns how index changes are propgated (locally, or remotely via JMS/JGroups)

Future index manager implementations will benefit from this clear separation as they can be used in conjunction with the different backends (local, JMS, JGgroups) "for free".