@Override
        public String toString() {
            if (isEmpty()) return "move none";
            return super.toString() + " [skew reduction "  + netSkewReduction + "]";
        }
We do this here rather than in MetricsReporter because it is expensive and frequent updates are unnecessary
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/Rebalancer.java