使用Elastic Search 5.5.0获得最佳性能时如何正确关闭原始RestClient？

使用 Spring Boot 1.5.4.RELEASE Microservice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,但经过一堆点击后,客户端应用程序报告HTTP 500错误,这是日志文件中出现的：

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]

在SearchController内部(//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...

    }
}

显而易见的是,在调用restClient.performRequest()方法之后它从未关闭过……

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()方法的信息,但我对线程缺乏经验,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一堆套接字资源的最佳方法吗？
>如果有人能够向我展示一种更好的方法来使用弹性搜索的低级RestClient意味着它不会导致套接字资源未被释放导致HTTP 500的相同问题,我将不胜感激.我是否应该使用restClient. performRequestAsync？有人可以提供一个例子吗？

感谢您抽出时间来阅读…

在每个请求上创建一个RestClient并不是一个好习惯.您应该通过配置bean创建一个单独的实例,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();
    }
}

然后在您的SearchController类中,您可以像这样注入它(并且还在容器关闭时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);
        }
    }

}