NameNode '192.168.1.164:9000'

　　以上是我们安装完成，并且正常运行后的HDFS状态页面（访问地址：http://210.66.44.88:50070/dfshealth.jsp），其中的Browse the filesystem 是查看文件系统的入口，但是有可能会出现无法访问的问题，我就遇到过，上网查了很久的解决办法都无果，后来我通过firebug拦截请求发现，Browse the filesystem这个链接的页面会跳转到另外一个页面，而这个页面的地址是http://192.168.1.164:50075/browseDirectory.jsp?namenodeInfoPort=50070&dir=%2F（ 192.168.1.164是服务器的内网地址，在masters和slaves文件中配置的是局域网IP），但是需要通过外网才能访问（类似于http://210.66.44.88:50075/browseDirectory.jsp?namenodeInfoPort=50070&dir=%2F才行），这就是问题所在。

　　我们来看看nn_browsedfscontent.jsp的源代码：

Java代码  

1. package org.apache.hadoop.hdfs.server.namenode;   
2.   
3. import java.io.IOException;   
4. import java.net.InetAddress;   
5. import java.net.InetSocketAddress;   
6. import java.net.URLEncoder;   
7. import java.util.Vector;   
8. import javax.servlet.ServletConfig;   
9. import javax.servlet.ServletContext;   
10. import javax.servlet.ServletException;   
11. import javax.servlet.http.HttpServletRequest;   
12. import javax.servlet.http.HttpServletResponse;   
13. import javax.servlet.http.HttpSession;   
14. import javax.servlet.jsp.JspFactory;   
15. import javax.servlet.jsp.JspWriter;   
16. import javax.servlet.jsp.PageContext;   
17. import javax.servlet.jsp.SkipPageException;   
18. import org.apache.hadoop.util.ServletUtil;   
19. import org.apache.jasper.runtime.HttpJspBase;   
20. import org.apache.jasper.runtime.JspSourceDependent;   
21. import org.apache.jasper.runtime.ResourceInjector;   
22.   
23. public final class nn_005fbrowsedfscontent_jsp extends HttpJspBase   
24.   implements JspSourceDependent   
25. {   
26.   private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();   
27.   private static Vector _jspx_dependants;   
28.   private ResourceInjector _jspx_resourceInjector;   
29.   
30.   //此处是将请求随机转发到一个DataNode节点上   
31.   public void redirectToRandomDataNode(NameNode nn, HttpServletResponse resp)   
32.     throws IOException   
33.   {   
34.     String nodeToRedirect;   
35.     int redirectPort;   
36.     FSNamesystem fsn = nn.getNamesystem();   
37.     String datanode = fsn.randomDataNode();   
38.   
39.     if (datanode != null) {   
40.       redirectPort = Integer.parseInt(datanode.substring(datanode.indexOf(58) + 1));   
41.       nodeToRedirect = datanode.substring(0, datanode.indexOf(58));   
42.     }   
43.     else {   
44.       nodeToRedirect = nn.getHttpAddress().getHostName();   
45.       redirectPort = nn.getHttpAddress().getPort();   
46.     }   
47.     // 此处是得到服务器的名称（hostname）   
48.     String fqdn = InetAddress.getByName(nodeToRedirect).getCanonicalHostName();   
49.     String redirectLocation = "http://" + fqdn + ":" + redirectPort + "/browseDirectory.jsp?namenodeInfoPort=" + nn.getHttpAddress().getPort() + "&dir=" + URLEncoder.encode("/", "UTF-8");   
50.   
51.     resp.sendRedirect(redirectLocation);   
52.   }   
53.   
54.   public Object getDependants()   
55.   {   
56.     return _jspx_dependants;   
57.   }   
58.   
59.   public void _jspService(HttpServletRequest request, HttpServletResponse response)   
60.     throws IOException, ServletException   
61.   {   
62.     PageContext pageContext = null;   
63.     HttpSession session = null;   
64.     ServletContext application = null;   
65.     ServletConfig config = null;   
66.     JspWriter out = null;   
67.     Object page = this;   
68.     JspWriter _jspx_out = null;   
69.     PageContext _jspx_page_context = null;   
70.     try  
71.     {   
72.       response.setContentType("text/html; charset=UTF-8");   
73.       pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true);   
74.   
75.       _jspx_page_context = pageContext;   
76.       application = pageContext.getServletContext();   
77.       config = pageContext.getServletConfig();   
78.       session = pageContext.getSession();   
79.       out = pageContext.getOut();   
80.       _jspx_out = out;   
81.       this._jspx_resourceInjector = ((ResourceInjector)application.getAttribute("com.sun.appserv.jsp.resource.injector"));   
82.   
83.       out.write(10);   
84.       out.write("\n\n<html>\n\n<title></title>\n\n<body>\n");   
85.   
86.       NameNode nn = (NameNode)application.getAttribute("name.node");   
87.       redirectToRandomDataNode(nn, response);   
88.   
89.       out.write("\n<hr>\n\n<h2>Local logs</h2>\n<a href=\"/logs/\">Log</a> directory\n\n");   
90.   
91.       out.println(ServletUtil.htmlFooter());   
92.   
93.       out.write(10);   
94.     } catch (Throwable t) {   
95.       if (!(t instanceof SkipPageException)) {   
96.         out = _jspx_out;   
97.         if ((out != null) && (out.getBufferSize() != 0))   
98.           out.clearBuffer();   
99.         if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);   
100.       }   
101.     } finally {   
102.       _jspxFactory.releasePageContext(_jspx_page_context);   
103.     }   
104.   }   
105. }  

package org.apache.hadoop.hdfs.server.namenode;

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.URLEncoder;
import java.util.Vector;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.SkipPageException;
import org.apache.hadoop.util.ServletUtil;
import org.apache.jasper.runtime.HttpJspBase;
import org.apache.jasper.runtime.JspSourceDependent;
import org.apache.jasper.runtime.ResourceInjector;

public final class nn_005fbrowsedfscontent_jsp extends HttpJspBase
  implements JspSourceDependent
{
  private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();
  private static Vector _jspx_dependants;
  private ResourceInjector _jspx_resourceInjector;

  //此处是将请求随机转发到一个DataNode节点上
  public void redirectToRandomDataNode(NameNode nn, HttpServletResponse resp)
    throws IOException
  {
    String nodeToRedirect;
    int redirectPort;
    FSNamesystem fsn = nn.getNamesystem();
    String datanode = fsn.randomDataNode();

    if (datanode != null) {
      redirectPort = Integer.parseInt(datanode.substring(datanode.indexOf(58) + 1));
      nodeToRedirect = datanode.substring(0, datanode.indexOf(58));
    }
    else {
      nodeToRedirect = nn.getHttpAddress().getHostName();
      redirectPort = nn.getHttpAddress().getPort();
    }
    // 此处是得到服务器的名称（hostname）
    String fqdn = InetAddress.getByName(nodeToRedirect).getCanonicalHostName();
    String redirectLocation = "http://" + fqdn + ":" + redirectPort + "/browseDirectory.jsp?namenodeInfoPort=" + nn.getHttpAddress().getPort() + "&dir=" + URLEncoder.encode("/", "UTF-8");

    resp.sendRedirect(redirectLocation);
  }

  public Object getDependants()
  {
    return _jspx_dependants;
  }

  public void _jspService(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
  {
    PageContext pageContext = null;
    HttpSession session = null;
    ServletContext application = null;
    ServletConfig config = null;
    JspWriter out = null;
    Object page = this;
    JspWriter _jspx_out = null;
    PageContext _jspx_page_context = null;
    try
    {
      response.setContentType("text/html; charset=UTF-8");
      pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true);

      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;
      this._jspx_resourceInjector = ((ResourceInjector)application.getAttribute("com.sun.appserv.jsp.resource.injector"));

      out.write(10);
      out.write("\n\n<html>\n\n<title></title>\n\n<body>\n");

      NameNode nn = (NameNode)application.getAttribute("name.node");
      redirectToRandomDataNode(nn, response);

      out.write("\n<hr>\n\n<h2>Local logs</h2>\n<a href=\"/logs/\">Log</a> directory\n\n");

      out.println(ServletUtil.htmlFooter());

      out.write(10);
    } catch (Throwable t) {
      if (!(t instanceof SkipPageException)) {
        out = _jspx_out;
        if ((out != null) && (out.getBufferSize() != 0))
          out.clearBuffer();
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

　　从代码可以看出，当我们点击Browse the filesystem 时后台会将请求随机转发到一台DataNode节点，使用的是slaves文件中配置的服务器列表所反解的域名或主机名，而通过局域网IP未能反解出域名和主机名，所以用的是IP，这样就出问题了，解决办法有两个：视redirectToRandomDataNode方法内生成的URL而定，如果反转域名是主机名的话，你只需要修改本地HOSTS映射就可以了（推荐使用Windows Hosts Editor，软件地址：http://yymmiinngg.iteye.com/blog/360779）；如果反转出的域名是主机局域网IP的话，那就需要配置slaves和masters使用域名或外网IP