Java High Level Rest Client多搜索API在Elasticsearch 8.3.2中无法使用

问题根源 #

ES 8.x版本彻底移除了文档类型（_type）的概念，而7.17.5的Java High Level Rest Client在构建MultiSearch请求时，会自动在每个子请求的元数据部分带上types字段，这在ES8.x中属于非法参数，即使开启API兼容模式也无法绕过这个限制。

解决方案 #

给每个SearchRequest显式设置空的类型数组，让客户端不再生成types相关的元数据字段：

修改后的代码如下：

SearchSourceBuilder metaDataSearch = new SearchSourceBuilder();
// 给SearchRequest添加空类型数组，避免生成types元数据
org.elasticsearch.action.search.SearchRequest metaSearch = new org.elasticsearch.action.search.SearchRequest()
        .source(metaDataSearch)
        .indices(indexName)
        .types(new String[0]);

SearchSourceBuilder keywordExactRequestBuilder = new SearchSourceBuilder().size(10);
keywordExactRequestBuilder.query(QueryBuilders.matchAllQuery());
// 同样给第二个SearchRequest设置空类型数组
org.elasticsearch.action.search.SearchRequest keywordExactRequestSearch = new org.elasticsearch.action.search.SearchRequest()
        .source(keywordExactRequestBuilder)
        .indices(indexName)
        .types(new String[0]);

MultiSearchRequest multiSearchRequest = new MultiSearchRequest()
        .add(metaSearch)
        .add(keywordExactRequestSearch);

MultiSearchResponse multiSearchResponse = null;
try {
    multiSearchResponse = elasticClient.msearch(multiSearchRequest, RequestOptions.DEFAULT);
} catch (IOException e) {
    e.printStackTrace();
}

补充检查 #

如果上述修改后仍有问题，请确认你的RestHighLevelClient是否正确配置了ES7兼容请求头：

RestHighLevelClient elasticClient = new RestHighLevelClient(
        RestClient.builder(new HttpHost("your-es-host", 9200, "http"))
                .setHttpClientConfigCallback(httpClientBuilder ->
                        httpClientBuilder.addInterceptorLast((HttpRequestInterceptor) (request, context) -> {
                            // 添加兼容ES7的请求头
                            request.addHeader("Accept", "application/vnd.elasticsearch+json;compatible-with=7");
                        })
                )
);

内容的提问来源于stack exchange，提问作者Sheik Syed