private void setContainerAsIndexingCluster(List<SearchNode> cluster,
                                                   IndexingDocproc indexingDocproc,
                                                   Content content,
                                                   ConfigModelContext modelContext,
                                                   ApplicationConfigProducerRoot root) {
            if (content.containers.isEmpty()) {
                createImplicitIndexingCluster(cluster, indexingDocproc, content, modelContext, root);
            } else {
                ContainerCluster<?> targetCluster = getContainerWithDocproc(content.containers);
                if (targetCluster == null)
                    targetCluster = getContainerWithSearch(content.containers);
                if (targetCluster == null)
                    targetCluster = content.containers.iterator().next().getCluster();

                addDocproc(targetCluster);
                indexingDocproc.setClusterName(targetCluster.getName());
                addIndexingChainsTo(targetCluster, content, indexingDocproc);
            }
        }
Select/creates and initializes the indexing cluster coupled to this
config-model/src/main/java/com/yahoo/vespa/model/content/Content.java