Ambari won't restart: DB check failed - hortonworks-data-platform

Question

When I restarted my cluster, ambari didn't start because of a db check failed config:
sudo service ambari-server restart --skip-database-check
Using python /usr/bin/python
Restarting ambari-server
Waiting for server stop...
Ambari Server stopped
Ambari Server running with administrator privileges.
Organizing resource files at /var/lib/ambari-server/resources...
Ambari Server is starting with the database consistency check skipped. Do not make any changes to your cluster topology or perform a cluster upgrade until you correct the database consistency issues. See "/var/log/ambari-server/ambari-server-check-database.log" for more details on the consistency issues.
Server PID at: /var/run/ambari-server/ambari-server.pid
Server out at: /var/log/ambari-server/ambari-server.out
Server log at: /var/log/ambari-server/ambari-server.log
Waiting for server start.....................
DB configs consistency check failed. Run "ambari-server start --skip-database-check" to skip. You may try --auto-fix-database flag to attempt to fix issues automatically. If you use this "--skip-database-check" option, do not make any changes to your cluster topology or perform a cluster upgrade until you correct the database consistency issues. See /var/log/ambari-server/ambari-server-check-database.log for more details on the consistency issues.
ERROR: Exiting with exit code -1.
REASON: Ambari Server java process has stopped. Please check the logs for more information.
I looked in the logs in "/var/log/ambari-server/ambari-server-check-database.log", and I saw:
2017-08-23 08:16:13,445 INFO - Checking Topology tables
2017-08-23 08:16:13,447 ERROR - Your topology request hierarchy is not complete for each row in topology_request should exist at least one raw in topology_logical_request, topology_host_request, topology_host_task, topology_logical_task.
I tried both options --auto-fix-database and --skip-database-check, it didn't work.

Answer 1

It seems that postgresql didn't start correctly, and even if in the log of Ambari there was no mention of postgresql not started or not available, but it was weird that ambari couldn't access to the topology configuration stored in it.
sudo service postgresql restart
Stopping postgresql service: [ OK ]
Starting postgresql service: [ OK ]
It did the trick:
sudo service ambari-server restart
Using python /usr/bin/python
Restarting ambari-server
Ambari Server is not running
Ambari Server running with administrator privileges.
Organizing resource files at /var/lib/ambari-server/resources...
Ambari database consistency check started...
Server PID at: /var/run/ambari-server/ambari-server.pid
Server out at: /var/log/ambari-server/ambari-server.out
Server log at: /var/log/ambari-server/ambari-server.log
Waiting for server start.........
Server started listening on 8080