使用 Elastic Search 5.5.0 时如何正确关闭 Raw RestClient 以获得最佳性能？

Question

我正在使用 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。

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>

一切设置正确，但经过多次点击后，客户端应用程序报告 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]

SearchController 内部（// 注释后的第二行是第 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，调用了restClient.performRequest()方法后它从来没有关闭过……

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...

此外，请阅读有关 restClient.performRequestAsync() 方法的信息，但我对线程有些缺乏经验，并且文档中的描述含糊不清。

问题：

1. 我的解决方案是处理和关闭一堆套接字资源的最佳方式吗？

2. 如果有人能告诉我一个更好的方法来使用 Elastic Search 的低级别 RestClient 将不胜感激，因为它不会导致与未释放套接字资源导致 HTTP 500 相同的问题。应该我正在使用 restClient.performRequestAsync？有人可以举个例子吗？

感谢您抽出宝贵时间阅读本文...

Answer 1

对每个请求都创建RestClient 不是一个好习惯。您应该通过如下配置 bean 创建单个实例：

@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（并且还添加一个清理方法以在您的容器出现故障时关闭 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);
        }
    }

}