RPCTarget getTarget(long now) {
            if (index >= targets.length) {
                index = 0;
            }
            RPCTarget target = targets[index];
            if (target.getJRTTarget().isValid()) {
                target.addRef();
                lastUse = now;
                index++;
                return target;
            }
            return null;
        }
Implements a helper class holds the necessary reference and timestamp of a target. The lastUse member is updated
when a call to {@link RPCTargetPool#flushTargets(boolean)} iterates over an active target.
messagebus/src/main/java/com/yahoo/messagebus/network/rpc/RPCTargetPool.java