Hadoop启动之后datanode进程在 但50070页面Live Nodes为0

当正常启动hadoop之后，一般进程都在，而且50070端口可以访问，但Live Nodes为0，这里可能有多种原因造成这样：

1、/etc/hosts 中的ip映射不对

2、master与slave之间不能互通

3、hadoop配置文件有错

在子节点中查看日志，

2018-01-03 09:26:48,488 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:26:49,489 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:26:50,490 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:26:51,494 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 5 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:26:52,495 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 6 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:26:53,496 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 7 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:26:54,497 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 8 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:26:55,498 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:27:26,510 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2018-01-03 09:27:27,511 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: hbase1/192.168.10.101:8031. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)

说明子节点无法访问到主节点，再去看了/etc/hosts文件：

#127.0.0.1      localhost
172.17.168.96  hbase1
192.168.10.101 hbase1
192.168.10.102 hbase2
192.168.10.103 hbase3
192.168.10.104 hbase4
192.168.10.105 hbase5
192.168.10.106 hbase6
192.168.10.107 hbase7
#backup cluster
192.168.20.101  bhbase1
192.168.20.102  bhbase2
192.168.20.103  bhbase3
192.168.20.104  bhbase4
192.168.20.105  bhbase5
192.168.20.106  bhbase6
192.168.20.107  bhbase7

其中hbase1（即主节点）映射了两个ip，但一般在linux中默认只会取hosts中配置的第一条主机名映射来使用，对于172.17.168.96这个ip，因为子节点配置了内网ip，所以访问不到。

解决方法就是将外网ip注释掉。

#127.0.0.1      localhost
#172.17.168.96  hbase1
192.168.10.101 hbase1
192.168.10.102 hbase2
192.168.10.103 hbase3
192.168.10.104 hbase4
192.168.10.105 hbase5
192.168.10.106 hbase6
192.168.10.107 hbase7
#backup cluster
192.168.20.101  bhbase1
192.168.20.102  bhbase2
192.168.20.103  bhbase3
192.168.20.104  bhbase4
192.168.20.105  bhbase5
192.168.20.106  bhbase6
192.168.20.107  bhbase7

然后重启hadoop即可。

=======================

还有一个问题就是，正常启动了hadoop之后，50070端口可以正常访问，但是8088端口访问不了，解决方法：

修改配置文件yarn-site.xml 中的

       yarn.resourcemanager.webapp.address
       hbase1:8088

修改后为：

       yarn.resourcemanager.webapp.address
       172.17.168.96:8088

这里不能用主机名，而应该用外网ip。每一台子节点都要修改，修改完成之后重启hadoop即可。

这样8088就能够正常访问。