Cascading thread fail.

[prataprc]

rdms index, by default, support concurrent thread safe API. Also some components within rdms spawn threads. This means, both locally spawned threads and rdms-handles that are used by application threads can suffer failure, in which case the failure must cascade across all the thread.

IMHO this is a bit early to work out a cascading failure mechanics. We may first have characterize the index functions and performance to implement the right method for cascading.