hdfs支持双栈ipv4和ipv6

2017-11-20

前言

ipv6标准制定了这么多年，终于要开始被大力推进了。最近要求hdfs既要支持ipv4，又要支持ipv6。所以特意研究了，怎么同时能支持ipv4和ipv6。

理论基础

ipv4和ipv6都是属于网络层，我们平常做的程序很少有机会去做到网络层，除非做的路由器和交换机。我们开发的程序大都是在传输层以上，基于tcp协议或者udp的协议。所以，我猜测应该我需要做的东西不是很多。找了找java建立网络的相关api。果然就被我发现了。

/**
    * Create a server with the specified port, listen backlog, and
    * local IP address to bind to.  The <i>bindAddr</i> argument
    * can be used on a multi-homed host for a ServerSocket that
    * will only accept connect requests to one of its addresses.
    * If <i>bindAddr</i> is null, it will default accepting
    * connections on any/all local addresses.
    * The port must be between 0 and 65535, inclusive.
    * A port number of {@code 0} means that the port number is
    * automatically allocated, typically from an ephemeral port range.
    * This port number can then be retrieved by calling
    * {@link #getLocalPort getLocalPort}.
    *
    * <P>If there is a security manager, this method
    * calls its {@code checkListen} method
    * with the {@code port} argument
    * as its argument to ensure the operation is allowed.
    * This could result in a SecurityException.
    *
    * The {@code backlog} argument is the requested maximum number of
    * pending connections on the socket. Its exact semantics are implementation
    * specific. In particular, an implementation may impose a maximum length
    * or may choose to ignore the parameter altogther. The value provided
    * should be greater than {@code 0}. If it is less than or equal to
    * {@code 0}, then an implementation specific default will be used.
    * <P>
    * @param port  the port number, or {@code 0} to use a port
    *              number that is automatically allocated.
    * @param backlog requested maximum length of the queue of incoming
    *                connections.
    * @param bindAddr the local InetAddress the server will bind to
    *
    * @throws  SecurityException if a security manager exists and
    * its {@code checkListen} method doesn't allow the operation.
    *
    * @throws  IOException if an I/O error occurs when opening the socket.
    * @exception  IllegalArgumentException if the port parameter is outside
    *             the specified range of valid port values, which is between
    *             0 and 65535, inclusive.
    *
    * @see SocketOptions
    * @see SocketImpl
    * @see SecurityManager#checkListen
    * @since   JDK1.1
    */
   public ServerSocket(int port, int backlog, InetAddress bindAddr) throws IOException {
       setImpl();
       if (port < 0 || port > 0xFFFF)
           throw new IllegalArgumentException(
                      "Port value out of range: " + port);
       if (backlog < 1)
         backlog = 50;
       try {
           bind(new InetSocketAddress(bindAddr, port), backlog);
       } catch(SecurityException e) {
           close();
           throw e;
       } catch(IOException e) {
           close();
           throw e;
       }
   }

我们在建离socket连接，就是tcp的连接的时候，需要传递三个参数。我去查了下这三个数的含义。从上面的注释可以发现，port表示要绑定的端口号，backlog等待建立连接的最大连接数，binAddr则就是要绑定的端口号。如果不传入binAddr这个参数，那么就会默认监听这台机器上所有地址。

那么问题，基本上就简单解决了好多，我只要在建立rpc请求的时候，不绑定ip地址和端口号，那么我不就可以同时监听ipv4和ipv6的地址么。果然，我在hdfs中找到了相关的配置项。

<property>
  <name>dfs.namenode.http-bind-host</name>
  <value></value>
  <description>
    The actual adress the HTTP server will bind to. If this optional address
    is set, it overrides only the hostname portion of dfs.namenode.http-address.
    It can also be specified per name node or name service for HA/Federation.
    This is useful for making the name node HTTP server listen on all
    interfaces by setting it to 0.0.0.0.
  </description>
</property>

果然配置成0.0.0.0，namenode的50070端口，ipv4和ipv6的端口都可以访问。