Ambari有时候在重启集群或者进行某些操作时，agent节点会出现hearbeat lost的问题
解决方法：
重启ambari-agent，ambari-agent restart
如果上述方法没法解决问题，进入该节点，查看agent的日志。
如果显示异常如下：
异常信息
File “/usr/lib/python2.6/site-packages/ambari_agent/Controller.py”, line 545, in sendRequest
raise IOError(‘Request to {0} failed due to {1}’.format(url, str(exception)))
IOError: Request to https://localhost:8441/agent/v1/register/namenode.exterrocloud.info
failed due to EOF occurred in violation of protocol (_ssl.c:661)
ERROR 2018-04-09 07:09:38,185 Controller.py:227 –
Error:Request to https://localhost:8441/agent/v1/register/namenode.exterrocloud.info
failed due to EOF occurred in violation of protocol (_ssl.c:661)
WARNING 2018-04-09 07:09:38,185 Controller.py:228 – Sleeping for 27 seconds and
then trying again
主要异常
“IOError: Request to https://localhost:8441/agent/v1/register/namenode.exterrocloud.info failed due to EOF occurred in violation of protocol (_ssl.c:661)” when starting an Ambari agent
可按照下面方法进行解决：
修改失去心跳节点的ambari-agent.ini配置文件，一般目录为：/etc/ambari-agent/conf/ambari-agent.ini
vim /etc/ambari-agent/conf/ambari-agent.ini
在[security] 新增如下一行
[security]
force_https_protocol=PROTOCOL_TLSv1_2
然后重启ambari-agent。
