private static double resourceUsageOf(String type, ContentNode node) {
        var result = node.resourceUsageOf(type);
        return result.isPresent() ? result.get().getUsage() : 0.0;
    }
Represents resource usage stats for the cluster that are exposed as metrics.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ResourceUsageStats.java