今天我也遇到了这个问题,重启也没有解决，后来按照下面的大神发现原因是有一个几点的免密有问题。
大神Balkrushna Patil的答案
We need to make sure below point in heart beat lost host.
check firewall status. It should be stop.
service iptables stop
check /etc/ambari-agent/conf/ambari-agent.ini file.
in ambari-agent file hostname entry should be
hostname = ambariservernodehost
ambariservernodehost should be present in /etc/hosts file
openssl version should be upgraded.
Stop ambari-server
Stop ambari-agent service on all nodes
Start ambari-agent service on all nodes
Start ambari-server server
