Mistral API start without DB

gistfile1.txt

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Mistral Workflow Service, version 5.1.0

Launching server components ['api']...
2018-01-26 09:35:42.900 1 WARNING oslo_config.cfg [-] Option "rpc_conn_pool_size" from group "DEFAULT" is deprecated. Use option "rpc_conn_pool_size" from group "oslo_messaging_rabbit".
2018-01-26 09:35:47.930 1 CRITICAL Mistral [-] Unhandled error: DBError: Failed to setup database: (psycopg2.OperationalError) could not translate host name "postgres" to address: Try again
2018-01-26 09:35:47.930 1 ERROR Mistral Traceback (most recent call last):
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/usr/local/bin/mistral-server", line 10, in <module>
2018-01-26 09:35:47.930 1 ERROR Mistral     sys.exit(main())
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/home/mistral/mistral/cmd/launch.py", line 211, in main
2018-01-26 09:35:47.930 1 ERROR Mistral     launch_any(set(cfg.CONF.server))
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/home/mistral/mistral/cmd/launch.py", line 108, in launch_any
2018-01-26 09:35:47.930 1 ERROR Mistral     LAUNCH_OPTIONS[option]()
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/home/mistral/mistral/cmd/launch.py", line 98, in launch_api
2018-01-26 09:35:47.930 1 ERROR Mistral     server = api_service.WSGIService('mistral_api')
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/home/mistral/mistral/api/service.py", line 29, in __init__
2018-01-26 09:35:47.930 1 ERROR Mistral     self.app = app.setup_app()
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/home/mistral/mistral/api/app.py", line 54, in setup_app
2018-01-26 09:35:47.930 1 ERROR Mistral     db_api_v2.setup_db()
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/home/mistral/mistral/db/v2/api.py", line 29, in setup_db
2018-01-26 09:35:47.930 1 ERROR Mistral     IMPL.setup_db()
2018-01-26 09:35:47.930 1 ERROR Mistral   File "/home/mistral/mistral/db/v2/sqlalchemy/api.py", line 73, in setup_db
2018-01-26 09:35:47.930 1 ERROR Mistral     raise exc.DBError("Failed to setup database: %s" % e)
2018-01-26 09:35:47.930 1 ERROR Mistral DBError: Failed to setup database: (psycopg2.OperationalError) could not translate host name "postgres" to address: Try again