Hadoop 多节点集群：异常：java.net.ConnectException：连接被拒绝

Question

我已经使用http://pingax.com/install-apache-hadoop-ubuntu-cluster-setup/设置了4个节点的hadoop集群：

名称节点：node04 数据节点：node01 数据节点：node02 数据节点：node03

我只能看到集群中运行的两个节点（node01、node03）。 Node02 有一个日志，错误消息为：

2015-12-11 10:15:18,698 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: node04/127.17.0.224:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2015-12-11 10:15:19,699 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: node04/127.17.0.224:9000. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2015-12-11 10:15:20,699 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: node04/127.17.0.224:9000. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)

每个节点 /etc/hosts 包含以下内容：

127.0.0.1       localhost

127.17.0.221    node01
127.17.0.222    node02
127.17.0.223    node03
127.17.0.224    node04
# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

并且 /etc/hadoop/masters 包含 node04，/etc/hadoop/slaves 包含 node01 node02 和 node03

您能帮我了解如何到达吗？ 谢谢！

Answer 1

执行以下操作：

1. 转到node02并运行telnet node04 9000和ping node04命令 确认 node02 和 node04 之间存在连接
2. 在所有节点上检查 core-site.xml 和 hdfs-site.xml 内容是否相同

Answer 2

1. 检查 ssh 和 sshd
2. 节点间ssh连接
3. 检查端口绑定详细信息 (Hadoop Datanodes cannot find NameNode)

另请参阅https://wiki.apache.org/hadoop/ServerNotAvailable