public static Function<String, String> indexNameConverter(String namespace) {
        return indexName -> {
            if (StringUtil.isNotEmpty(namespace)) {
                return namespace + "_" + indexName;
            }
            return indexName;
        };
    }
The storage provider for ElasticSearch 6/7 and OpenSearch 1.x.
oap-server/server-storage-plugin/storage-elasticsearch-plugin/src/main/java/org/apache/skywalking/oap/server/storage/plugin/elasticsearch/StorageModuleElasticsearchProvider.java