Hortonworks Nodemanager启动但失败：连接拒绝：8042 解决方法

问题描述：

Connection failed to http://IP:8042/ws/v1/node/info (Traceback (most recent call last):
  File "/var/lib/ambari-agent/cache/stacks/HDP/3.0/services/YARN/package/alerts/alert_nodemanager_health.py", line 171, in execute
    url_response = urllib2.urlopen(query, timeout=connection_timeout)
  File "/usr/lib64/python2.7/urllib2.py", line 154, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib64/python2.7/urllib2.py", line 431, in open
    response = self._open(req, data)
  File "/usr/lib64/python2.7/urllib2.py", line 449, in _open
    '_open', req)
  File "/usr/lib64/python2.7/urllib2.py", line 409, in _call_chain
    result = func(*args)
  File "/usr/lib64/python2.7/urllib2.py", line 1244, in http_open
    return self.do_open(httplib.HTTPConnection, req)
  File "/usr/lib64/python2.7/urllib2.py", line 1214, in do_open
    raise URLError(err)
URLError: 

在ambari中重启nodemanager有时会长时间提示在检验yarn日志目录，最终导致重启失败，提示如下：
造成该原因的是yarn日志目录下产生太多临时文件，把这些无用的文件直接删除，并删除了/ var/log/hadoop-yarn/nodemanager/recovery-state目录并再次启动了YARN，虽然启动的时候，会成功，但是过来一会就有自己停止了

rm -rf /data1/hadoop/yarn/*

然后尝试以下方式直接在命令行启动nodemanager：
查看8042端口，服务并没有启动,所以端口没有被监听

netstat -tnlpa | grep 8042

解决思路：
查看yarn-yarn-nodemanager.pid
yarn-yarn-nodemanager.pid 存在，但是值为空，进程没有启动

 程序日志路径：
/var/log/hadoop-yarn/yarn/yarn-yarn-nodemanager-*.log
/var/log/hadoop-yarn/yarn/yarn-yarn-nodemanager-*.out

尝试使用命令行手动启动NodeManager

su -l yarn -c "/usr/hdp/current/hadoop-yarn-nodemanager/sbin/yarn-daemon.sh start nodemanager"