private static Duration requireInterval(Duration interval) {
        Objects.requireNonNull(interval);
        if (interval.isNegative() || interval.isZero())
            throw new IllegalArgumentException("Interval must be positive, but was " + interval);
        return interval;
    }
Returns the initial delay of this calculated from cluster index of the hostname of this node, and the maintainer name.
vespajlib/src/main/java/com/yahoo/concurrent/maintenance/Maintainer.java