introduced a borrow queue to a Host that is used when there are no available connections. It could be nice to have a method on Session.State to request the size of that queue, similar to getInFlightQueries(Host).
Resolution: Since adding a method to Session.State would break API compatibility, we decided to only add this as Metrics.getRequestQueueDepth() (request-queue-depth)
Might also be good to add a meter to Metrics to monitor when requests get queued globally. We could also take it a step further and also monitor when a borrow request times out.