尽管超时，CloseableHttpClient.execute 每隔几周就会冻结一次

Question

我们有一个 groovy 单例，它使用池大小为 200 的 PoolingHttpClientConnectionManager(httpclient:4.3.6) 来处理与搜索服务的高并发连接并处理 xml 响应。

尽管有指定的超时时间，但它大约每月冻结一次，但其余时间运行正常。

下面的 groovy 单例。方法retrieveInputFromURL 似乎阻塞了client.execute(get);

@Singleton(strict=false)
class StreamManagerUtil {
   // Instantiate once and cache for lifetime of Signleton class

   private static PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager();

   private static CloseableHttpClient client;

   private static final IdleConnectionMonitorThread staleMonitor = new IdleConnectionMonitorThread(connManager);

   private int warningLimit;
   private int readTimeout;
   private int connectionTimeout;
   private int connectionFetchTimeout;

   private int poolSize;
   private int routeSize;

   PropertyManager propertyManager  = PropertyManagerFactory.getInstance().getPropertyManager("sebe.properties")

   StreamManagerUtil() {
      // Initialize all instance variables in singleton from properties file

      readTimeout = 6
      connectionTimeout = 6
      connectionFetchTimeout =6

      // Pooling
      poolSize = 200
      routeSize = 50

      // Connection pool size and number of routes to cache
      connManager.setMaxTotal(poolSize);
      connManager.setDefaultMaxPerRoute(routeSize);

      // ConnectTimeout : time to establish connection with GSA
      // ConnectionRequestTimeout : time to get connection from pool
      // SocketTimeout : waiting for packets form GSA

      RequestConfig config = RequestConfig.custom()
      .setConnectTimeout(connectionTimeout * 1000)
      .setConnectionRequestTimeout(connectionFetchTimeout * 1000)
      .setSocketTimeout(readTimeout * 1000).build();

      // Keep alive for 5 seconds if server does not have keep alive header
      ConnectionKeepAliveStrategy myStrategy = new ConnectionKeepAliveStrategy() {
         @Override
         public long getKeepAliveDuration(HttpResponse response, HttpContext context) {
            HeaderElementIterator it = new BasicHeaderElementIterator
               (response.headerIterator(HTTP.CONN_KEEP_ALIVE));
            while (it.hasNext()) {
               HeaderElement he = it.nextElement();
               String param = he.getName();
               String value = he.getValue();
               if (value != null && param.equalsIgnoreCase
                  ("timeout")) {
                  return Long.parseLong(value) * 1000;
               }
            }
            return 5 * 1000;
         }
      };

      // Close all connection older than 5 seconds. Run as separate thread.
      staleMonitor.start();
      staleMonitor.join(1000);

      client = HttpClients.custom().setDefaultRequestConfig(config).setKeepAliveStrategy(myStrategy).setConnectionManager(connManager).build();
   }     

   private retrieveInputFromURL (String categoryUrl, String xForwFor, boolean isXml) throws Exception {

      URL url = new URL( categoryUrl );

      GPathResult searchResponse = null
      InputStream inputStream = null
      HttpResponse response;
      HttpGet get;
      try {
         long startTime = System.nanoTime();

         get = new HttpGet(categoryUrl);
         response =  client.execute(get);

         int resCode = response.getStatusLine().getStatusCode();

         if (xForwFor != null) {
            get.setHeader("X-Forwarded-For", xForwFor)
         }

         if (resCode == HttpStatus.SC_OK) {
            if (isXml) {
               extractXmlString(response)
            } else {
               StringBuffer buffer = buildStringFromResponse(response)
               return buffer.toString();
            }
         }

      }
      catch (Exception e)
      {
         throw e;
      }
      finally {
         // Release connection back to pool
         if (response != null) {
            EntityUtils.consume(response.getEntity());
         }
      }

   }

   private extractXmlString(HttpResponse response) {
      InputStream inputStream = response.getEntity().getContent()

      XmlSlurper slurper = new XmlSlurper()
      slurper.setFeature("http://xml.org/sax/features/validation", false)
      slurper.setFeature("http://apache.org/xml/features/disallow-doctype-decl", false)
      slurper.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false)
      slurper.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false)

      return slurper.parse(inputStream)
   }

   private StringBuffer buildStringFromResponse(HttpResponse response) {
      StringBuffer buffer= new StringBuffer();
      BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
      String line = "";
      while ((line = rd.readLine()) != null) {
         buffer.append(line);
         System.out.println(line);
      }
      return buffer
   }

public class IdleConnectionMonitorThread extends Thread {

    private final HttpClientConnectionManager connMgr;
    private volatile boolean shutdown;

    public IdleConnectionMonitorThread
      (PoolingHttpClientConnectionManager connMgr) {
        super();
        this.connMgr = connMgr;
    }

    @Override
    public void run() {
        try {
            while (!shutdown) {
                synchronized (this) {
                    wait(5000);
                    connMgr.closeExpiredConnections();
                    connMgr.closeIdleConnections(10, TimeUnit.SECONDS);
                }
            }
        } catch (InterruptedException ex) {
            // Ignore
        }
    }
    public void shutdown() {
        shutdown = true;
        synchronized (this) {
            notifyAll();
        }
    }
}

我还在日志中发现了这一点，这让我相信它发生在等待响应数据时

java.net.SocketTimeoutException：在 java.net.SocketInputStream.read(SocketInputStream.java:150) 在 java.net.SocketInputStream.read(SocketInputStream.read) 的 java.net.SocketInputStream.socketRead0(Native Method) 读取超时java:121) 在 sun.security.ssl.InputRecord.readFully(InputRecord.java:465)

迄今为止的发现：

• 我们使用的是 java 1.8u25。在类似情况下存在未解决的问题 https://bugs.openjdk.java.net/browse/JDK-8075484
• HttpClient 有类似的报告 https://issues.apache.org/jira/browse/HTTPCLIENT-1589 但这已在 我们正在使用的 4.3.6 版本

问题

• 这可能是同步问题吗？据我了解，即使单例由多个线程访问，唯一的共享数据是缓存的 CloseableHttpClient
• 此代码是否存在其他根本性错误，可能导致此行为的方法？

Answer 1

我没有发现您的代码有任何明显错误。不过，我强烈建议在连接管理器上设置 SO_TIMEOUT 参数，以确保它在创建时应用于所有新套接字，而不是在请求执行时。

我还想知道“冻结”到底是什么意思。工作线程是否在等待从池中获取连接或等待响应数据时被阻塞？

还请注意，如果服务器继续发送块编码数据位，工作线程可能会出现“冻结”。像往常一样，客户端会话的连线/上下文日志会有很大帮助 http://hc.apache.org/httpcomponents-client-4.3.x/logging.html