Question

我使用Spring来实现以下目标：

在服务器上，我通过REST接口以XML格式接收数据。我想将数据转换为JSON并将其发布到另一个服务器。我的代码（我删除了一些敏感的类名/ URL以避免雇主的愤怒）看起来像这样：

主要/配置类：

package stateservice;

import org.apache.http.HttpHost;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
public class App {
    Logger log = LoggerFactory.getLogger(App.class);

    public static void main(String[] args) {
        System.out.println("Start!");
        SpringApplication.run(StateServiceApplication.class, args);
        System.out.println("End!");
    }

    @Bean
    public RestTemplate restTemplate() {
        log.trace("restTemplate()");
        HttpHost proxy = new HttpHost("proxy_url", 8080);
        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
        // Increase max total connection to 200
        cm.setMaxTotal(200);
        cm.setDefaultMaxPerRoute(50);

        RequestConfig requestConfig = RequestConfig.custom().setProxy(proxy).build();

        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
        httpClientBuilder.setDefaultRequestConfig(requestConfig);
        httpClientBuilder.setConnectionManager(cm);
        HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(
                httpClientBuilder.build());
        return new RestTemplate(requestFactory);
    }
}

表示RESTful接口的类：

package stateservice;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import foo.bar.XmlData

@RestController
public class StateController {

    private static Logger log = LoggerFactory.getLogger(DataController.class);

    @Autowired
    ForwarderService forwarder;


    @RequestMapping(value = "/data", method = RequestMethod.POST)
    public String postState(@RequestBody XmlData data) {
        forwarder.forward(data);
        return "Done!";
    }
}

最后，转发商：

package stateservice;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

import foo.bar.Converter;
import foo.bar.XmlData;

@Service
public class ForwarderService {
    private static Logger log = LoggerFactory.getLogger(ForwarderService.class);

    String uri = "forward_uri";

    @Autowired
    RestTemplate restTemplate;

    @Async
    public String forward(XmlData data) {
        log.trace("forward(...) - start");
        String json = Converter.convert(data);
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);

        ResponseEntity<String> response = restTemplate.postForEntity(uri,
                new HttpEntity<String>(json, headers), String.class);
        // responseEntity.getBody();
        // log.trace(responseEntity.toString());
        log.trace("forward(...) - end");
        return response.getBody();
    }
}

但是，Connection Manager似乎很少释放连接以供重用，此外，系统会被CLOSE_WAIT状态的连接充满（可以使用netstat看到）。池中的所有连接都被租用，但没有被释放，一旦CLOSE_WAIT状态的连接数达到ulimit，我就会得到“打开文件太多”-exceptions

由于代码的多线程特性，我怀疑套接字不能被关闭/连接被释放，因为其他一些线程是somhow阻止它们。

我非常感谢你能给我解决问题的任何帮助或暗示。

Answer 1

Apache HttpEntity有一个技巧 - 释放锁定连接 - 响应必须完全消耗和关闭。有关详细信息，请参阅EntityUtils和HttpEntity文档：

EntityUtils.consume(response);

从版本4.3开始，当在CloseableHttpResponse上调用#close（）方法时，Apache HttpClient会将连接释放回池中。

但是，自版本4.0.0-RELEASE以来，Spring Web支持此功能，请参阅HttpComponentsClientHttpResponse.java中的方法#close（）：

@Override
public void close() {
    // Release underlying connection back to the connection manager
    try {
        try {
            // Attempt to keep connection alive by consuming its remaining content
            EntityUtils.consume(this.httpResponse.getEntity());
        } finally {
            // Paranoia
            this.httpResponse.close();
        }
    }
    catch (IOException ignore) {
    }
}

成功的关键是标有“// Paranoia”的行 - 显式.close（）调用。它实际上将连接释放回池。

PoolingHttpClientConnectionManager不释放连接

1 个答案: