ClientCnxn: Session 0x0 for server null, unexpected error Connection refused

坑爹的异常！这个异常碰到过多次每次有可能会是不同的地方出现问题导致，

现在总结出来该异常的总体解决方向为：是zookeeper访问regionserver时候抛出的，一般是hbase-site.xml中的dns设置有问题，或者dns本身有问题，症状就为regionserver一个或者几个或者全部不能起动，以后再见Session 0x0，就朝着这个方向找吧。

这次抛出是dns服务器换机器了，结果配置文件没有改掉，今天优化hadoop配置参数重启之后就抛出这个一场了，修改后就没问题了。

配置参数记录如下：

<property>
    <name>hbase.zookeeper.dns.interface</name>
    <value>eth1</value>
    <description>The name of the Network Interface from which a ZooKeeper server
      should report its IP address.
    </description>
</property>
<property>
    <name>hbase.zookeeper.dns.nameserver</name>
    <value>X.X.X.111</value>
    <description>The host name or IP address of the name server (DNS)
      which a ZooKeeper server should use to determine the host name used by the
      master for communication and display purposes.
    </description>
</property>
<property>
    <name>hbase.regionserver.dns.interface</name>
    <value>eth1</value>
    <description>The name of the Network Interface from which a region server
      should report its IP address.
    </description>
</property>
<property>
    <name>hbase.regionserver.dns.nameserver</name>
    <value>X.X.X.111</value>
        <value>true</value>
        <description>Time difference of regionserver from master</description>
</property>
<property>
    <name>hbase.zookeeper.dns.interface</name>
    <value>eth1</value>
    <description>The name of the Network Interface from which a ZooKeeper server
      should report its IP address.
    </description>
</property>
<property>
    <name>hbase.zookeeper.dns.nameserver</name>
    <value>X.X.X.111</value>
    <description>The host name or IP address of the name server (DNS)
      which a ZooKeeper server should use to determine the host name used by the
      master for communication and display purposes.
    </description>
</property>
<property>
    <name>hbase.regionserver.dns.interface</name>
    <value>eth1</value>
    <description>The name of the Network Interface from which a region server
      should report its IP address.
    </description>
</property>
<property>
    <name>hbase.regionserver.dns.nameserver</name>
    <value>X.X.X.111</value>
    <description>The host name or IP address of the name server (DNS)
      which a region server should use to determine the host name used by the
      master for communication and display purposes.
    </description>
</property>
<property>
    <name>hbase.master.dns.interface</name>
    <value>eth1</value>
    <description>The name of the Network Interface from which a master
      should report its IP address.
    </description>
</property>
<property>
    <name>hbase.master.dns.nameserver</name>
    <value>X.X.X.111</value>
    <description>The host name or IP address of the name server (DNS)
      which a master should use to determine the host name used
      for communication and display purposes.
    </description>
</property>