使用Spring Boot 1.5.4.RELEASE微服务使用ElasticSearch提供的低级Rest Client连接到ElasticSearch 5.5.0实例。
的pom.xml
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.4.RELEASE</version>
</parent>
<dependencies>
<!-- Spring -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- Elasticsearch -->
<dependency>
<groupId>org.elasticsearch</groupId>
<artifactId>elasticsearch</artifactId>
<version>5.5.0</version>
</dependency>
<dependency>
<groupId>org.elasticsearch.client</groupId>
<artifactId>transport</artifactId>
<version>5.5.0</version>
</dependency>
<!-- Apache Commons -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.6</version>
</dependency>
<!-- Jackson -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.8.9</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.8.9</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.8.9</version>
</dependency>
<!-- Log4j -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<!-- JUnit -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!-- Swagger -->
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger2</artifactId>
<version>2.6.1</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger-ui</artifactId>
<version>2.6.1</version>
<scope>compile</scope>
</dependency>
</dependencies>
一切都设置正确，但经过一系列点击后，客户端应用报告了一个HTTP 500错误，这就是日志文件中出现的内容：
java.io.IOException: Too many open files
at sun.nio.ch.IOUtil.makePipe(Native Method) ~[na:1.8.0_141]
at sun.nio.ch.EPollSelectorImpl.<init>(EPollSelectorImpl.java:65) ~[na:1.8.0_141]
at sun.nio.ch.EPollSelectorProvider.openSelector(EPollSelectorProvider.java:36) ~[na:1.8.0_141]
at java.nio.channels.Selector.open(Selector.java:227) ~[na:1.8.0_141]
at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor.<init>(AbstractMultiworkerIOReactor.java:142) ~[httpcore-nio-4.4.5.jar!/:4.4.5]
at org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.<init>(DefaultConnectingIOReactor.java:79) ~[httpcore-nio-4.4.5.jar!/:4.4.5]
at org.apache.http.impl.nio.client.IOReactorUtils.create(IOReactorUtils.java:43) ~[httpasyncclient-4.1.3.jar!/:4.1.3]
at org.apache.http.impl.nio.client.HttpAsyncClientBuilder.build(HttpAsyncClientBuilder.java:666) ~[httpasyncclient-4.1.3.jar!/:4.1.3]
at org.elasticsearch.client.RestClientBuilder.createHttpClient(RestClientBuilder.java:202) ~[rest-5.5.0.jar!/:5.5.0]
at org.elasticsearch.client.RestClientBuilder.build(RestClientBuilder.java:180) ~[rest-5.5.0.jar!/:5.5.0]
at com.myapp.controller.SearchController.getSearchQueryResults(SearchController.java:94) ~[classes!/:1.0]
Inside SearchController（//注释之后的第二行是第94行）：
@RestController
@RequestMapping("/api/v1")
public class SearchController {
@RequestMapping(value = "/search", method = RequestMethod.GET, produces="application/json" )
public ResponseEntity<Object> getSearchQueryResults(@RequestParam(value = "criteria") String criteria) throws IOException {
// Setup HTTP Headers
HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", "application/json");
// Setup RestClient
RestClient restClient = RestClient.builder(new HttpHost("localhost", 9200))
.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
@Override
public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder requestConfigBuilder) {
return requestConfigBuilder.setConnectTimeout(5000).setSocketTimeout(60000);
}
}).setMaxRetryTimeoutMillis(60000).build();
// Setup query and send and return ResponseEntity...
}
}
很明显，在调用restClient.performRequest（）方法后它从未关闭过......
所以，我把它放到我的代码中：
Response response = null;
try {
// Submit Query and Obtain Response
response = restClient.performRequest("POST", endPoint, Collections.singletonMap("pretty", "true"), entity);
}
catch (IOException e) {
LOG.error("\n\n\tException: " + e + "\n\n");
e.printStackTrace();
}
finally {
restClient.close();
}
阅读Elastic Search的文档，了解RestClient类是线程安全的......
另外，请阅读有关restClient.performRequestAsync（）方法的内容，但对线程缺乏经验，文档中的描述含糊不清。
问题（S）：
我的解决方案是处理和关闭大量套接字资源的最佳方式吗？
如果有人可以向我展示一种更好的方法来使用低级RestClient和弹性搜索，我将不胜感激，因为它不会导致套接字资源未被释放导致HTTP 500的相同问题。我正在使用restClient.performRequestAsync？有人可以提供一个例子吗？
感谢您抽出宝贵时间阅读此内容......
答案 0 :(得分：8)
在每个请求上创建RestClient都不是一个好习惯。您应该通过配置bean创建单个实例，如下所示：
@Configuration
public class ElasticsearchConfig {
@Value("${elasticsearch.host}")
private String host;
@Value("${elasticsearch.port}")
private int port;
@Bean
public RestClient restClient() {
return RestClient.builder(new HttpHost(host, port))
.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
@Override
public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder requestConfigBuilder) {
return requestConfigBuilder.setConnectTimeout(5000).setSocketTimeout(60000);
}
}).setMaxRetryTimeoutMillis(60000).build();
}
}
然后在你的SearchController类中，你可以像这样注入它（并且当你的容器出现故障时还添加一个清理方法来关闭restClient实例）：
@RestController
@RequestMapping("/api/v1")
public class SearchController {
@Autowired
private RestClient restClient;
@RequestMapping(value = "/search", method = RequestMethod.GET, produces="application/json" )
public ResponseEntity<Object> getSearchQueryResults(@RequestParam(value = "criteria") String criteria) throws IOException {
// Setup HTTP Headers
HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", "application/json");
// Setup query and send and return ResponseEntity...
Response response = this.restClient.performRequest(...);
}
@PreDestroy
public void cleanup() {
try {
logger.info("Closing the ES REST client");
this.restClient.close();
} catch (IOException ioe) {
logger.error("Problem occurred when closing the ES REST client", ioe);
}
}
}