@Override
    public String toString() { return "metrics at " + at + ": " +
                                      load +
                                      " generation: " + generation +
                                      " inService: " + inService +
                                      " stable: " + stable +
                                      " queryRate: " + queryRate;
    }
The configuration generation at the time of this measurement, or -1 if not known
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/NodeMetricSnapshot.java