public RestTemplate getRestClient() {
        if (restTemplate != null) {
            return restTemplate;
        }
        try {
            synchronized (RestTemplate.class) {
                if (restTemplate == null) {
                    restTemplate = new RestTemplate();
                }
            }
        } catch (Exception e) {
            logger.error("get es high level client error", e);
        }
        return restTemplate;
    }
Get http rest client.

@return springframework RestTemplate
inlong-manager/manager-service/src/main/java/org/apache/inlong/manager/service/resource/sink/es/ElasticsearchConfig.java