HI @Jay Kumar SenSharma, Thanks for the reply. By setting the hostname of the machine running the ambari-server service, in the "/etc/hosts" file of each host machine, helped to solve the problem. Quick question: in the "/etc/hosts" file of each host machine, shall I only set the hostname of the machine running the ambari-server service, or shall I also write the hostname of the all hosts? Because my cluster is composed by serveral machines, and different services, such as, YARN, Spark, Mapreduce< HIVE etc. are running on different machines (for example, some machine are Nodemanager, other machine run the Hive server etc.).
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Suddenly, Ambari displayed heartbeat lost on all hosts as the following picture shows: I have tried to generate a new certificate for each host as showed at this link but it does not help. Fyi, on all my hosts the folder `/var/lib/ambari-agent/keys` is empty. If I execute the command `sudo ambari-agent start` I get the following error: Verifying Python version compatibility... Using python /usr/bin/python Checking for previously running Ambari Agent... /run/ambari-agent/ambari-agent.pid found with no process. Removing 3439... Starting ambari-agent Verifying ambari-agent process status... ERROR: ambari-agent start failed. For more details, see /var/log/ambari-agent/ambari-agent.out: ==================== Traceback (most recent call last): File "/usr/lib/python2.6/site-packages/ambari_agent/main.py", line 387, in <module> main(heartbeat_stop_callback) File "/usr/lib/python2.6/site-packages/ambari_agent/main.py", line 355, in main (retries, connected, stopped) = netutil.try_to_connect(server_url, MAX_RETRIES, logger) UnboundLocalError: local variable 'server_url' referenced before assignment ====================
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