private void setupTuning(ContentCluster c, ModelElement tuning) {
            ModelElement distribution = tuning.child("distribution");
            if (distribution != null) {
                String attr = distribution.stringAttribute("type");
                if (attr != null) {
                    if (attr.equalsIgnoreCase("strict")) {
                        c.distributionMode = DistributionMode.STRICT;
                    } else if (attr.equalsIgnoreCase("loose")) {
                        c.distributionMode = DistributionMode.LOOSE;
                    } else if (attr.equalsIgnoreCase("legacy")) {
                        c.distributionMode = DistributionMode.LEGACY;
                    } else {
                        throw new IllegalArgumentException("Distribution type " + attr + " not supported.");
                    }
                }
            }
            ModelElement merges = tuning.child("merges");
            if (merges != null) {
                Integer attr = merges.integerAttribute("max-nodes-per-merge");
                if (attr != null) {
                    c.maxNodesPerMerge = attr;
                }
            }
        }
The admin model of this system or null if none (which only happens in tests)
config-model/src/main/java/com/yahoo/vespa/model/content/cluster/ContentCluster.java