@Override
    void received(Node node, boolean busy) {
        node.metrics.incReceived();
        if (busy) {
            node.metrics.incBusy();
        }
    }
Will pick 2 random candidates and select the one with the least pending operations.

@author baldersheim
documentapi/src/main/java/com/yahoo/documentapi/messagebus/protocol/AdaptiveLoadBalancer.java