An interceptor that acts as a failover valve: it allows all invocations to go through as long
as there is no failover in progress (valve is open), and holds all invocations while client-side
failover is taking place (valve is closed).
This class stores message count informations for a given queue
At intervals this class samples the queue for message count data
Note that the underlying queue *does not* update statistics every time a message
is added since that would reall slow things down, instead we *sample* the queues at
regular intervals - this means we are less intrusive on the queue
By convention, we name durable topic message queue names in the following way:
This is a helper class to aid in converting between the string form and the client id
and subscription name and vice versa
Context.rebind() requires that all intermediate contexts and the target context (that named by
all but terminal atomic component of the name) must already exist, otherwise
NameNotFoundException is thrown.