We are facing Heartbeat lost for one of our node. All nodes ambari-agent is up and running fine even ambari-server too.
Done with restarting ambari-server and ambari-agent too but it dint resolved.
Have you looked at the Ambari Agent log on the node with the missing heartbeat? Anything useful there? Have you made sure that NTP (or equivalent) is running properly and there is no time drift?
Verify the hostname as seen by the ambari agent and server are the same
1. In the /var/log/ambari-agent/ambari-agent.log , search for socket.getfqdn, sample line below
hostname.py:106 - Read public hostname '<servername>' using socket.getfqdn()
2. Get the list of hosts from the api
Verify the FQDN <servername>