simplify main script

scripts/ucloud

@@ -1,49 +1,34 @@
 #!/usr/bin/env python3
 
 import argparse
-import multiprocessing as mp
 import logging
+import importlib
 
-from os.path import join as join_path
-from ucloud.sanity_checks import check
+# For the exception
+import decouple
+import sys
+
+COMMANDS = ['api', 'scheduler', 'host', 'filescanner', 'imagescanner', 'metadata']
 
 if __name__ == "__main__":
+    log = logging.getLogger("ucloud")
+
     arg_parser = argparse.ArgumentParser(prog='ucloud',
                                          description='Open Source Cloud Management Software')
-    arg_parser.add_argument('component',
-                            choices=['api', 'scheduler', 'host',
-                                     'filescanner', 'imagescanner',
-                                     'metadata'])
+    arg_parser.add_argument('component', choices=COMMANDS)
     arg_parser.add_argument('component_args', nargs='*')
     args = arg_parser.parse_args()
 
     try:
-        if args.component == 'api':
-            from ucloud.api.main import main
+        name = args.component
 
-            main()
-        elif args.component == 'host':
-            from ucloud.host.main import main
+        mod = importlib.import_module("ucloud.{}.main".format(name))
+        main = getattr(mod, "main")
+        main()
 
-            hostname = args.component_args
-            mp.set_start_method('spawn')
-            main(*hostname)
-        elif args.component == 'scheduler':
-            from ucloud.scheduler.main import main
-
-            main()
-        elif args.component == 'filescanner':
-            from ucloud.filescanner.main import main
-
-            main()
-        elif args.component == 'imagescanner':
-            from ucloud.imagescanner.main import main
-
-            main()
-        elif args.component == 'metadata':
-            from ucloud.metadata.main import main
-
-            main()
+    except decouple.UndefinedValueError as e:
+        print(e)
+        sys.exit(1)
 
     except Exception as e:
         logging.exception(e)