如何用RestHighLevelClient给某索引别名添加rollover策略

要使用RestHighLevelClient给ES中某个索引别名添加rollover策略，可以通过以下步骤实现：

1. 创建rollover策略配置：

可以使用以下代码创建rollover策略配置：

Map<String, Object> configMap = new HashMap<>();
configMap.put("max_age", "30d");
configMap.put("max_size", "50gb");

Map<String, Object> conditionsMap = new HashMap<>();
conditionsMap.put("conditions", configMap);

Map<String, Object> rolloverMap = new HashMap<>();
rolloverMap.put("name", "alias-name");
rolloverMap.put("alias", "index-alias");
rolloverMap.put("conditions", conditionsMap);

Map<String, Object> actionMap = new HashMap<>();
actionMap.put("rollover", rolloverMap);

Map<String, Object> settingsMap = new HashMap<>();
settingsMap.put("index.lifecycle.name", "rollover-policy");
settingsMap.put("index.lifecycle.rollover_alias", "index-alias");

Map<String, Object> policyMap = new HashMap<>();
policyMap.put("policy", settingsMap);
policyMap.put("actions", Collections.singletonList(actionMap));

IndexLifecyclePolicyRequest indexLifecyclePolicyRequest = new IndexLifecyclePolicyRequest("rollover-policy", policyMap);

其中，max_age属性为日志的最大保存时间，max_size属性为日志文件的最大大小，name属性为别名索引名称，alias属性为实际索引名称，index.lifecycle.name属性为策略名称，index.lifecycle.rollover_alias属性为别名索引名称。

2. 创建IndexLifecycleClient对象：

可以使用以下代码创建IndexLifecycleClient对象：

RestHighLevelClient client = new RestHighLevelClient(
        RestClient.builder(
                new HttpHost("localhost", 9200, "http")));
IndexLifecycleClient lifecycleClient = new RestHighLevelClient(client.getLowLevelClient()).indexLifecycle();

其中，HttpHost对象为ES集群的连接地址和端口号。

3. 创建并执行IndexLifecyclePolicyRequest对象：

可以使用以下代码创建并执行IndexLifecyclePolicyRequest对象：

CreateIndexLifecyclePolicyRequest createIndexLifecyclePolicyRequest = new CreateIndexLifecyclePolicyRequest(indexLifecyclePolicyRequest);
CreateIndexLifecyclePolicyResponse createIndexLifecyclePolicyResponse = lifecycleClient.createIndexLifecyclePolicy(createIndexLifecyclePolicyRequest, RequestOptions.DEFAULT);

通过以上步骤，就可以使用RestHighLevelClient给ES中某个索引别名添加rollover策略了。