Fix discovering container names

Make discover_container_name returning None, if the ps command failed
or returned nothing useful.

* For 'run', if no container name has been discovered, use its
  predictable (fixed) container service name.

* For 'exec', also raise an error, if no name has been discovered for
  the fixed/service container. Do not use additional checks as the
  None returned by discover_container_name() already tells us all we
  need to know about the subject container.

Related-Bug: #1839929

Co-Authored-By: Cédric Jeanneret <cjeanner@redhat.com>
Change-Id: I8a495d2c98617bb5edbe13ccf737d6c630eea7ad
Signed-off-by: Bogdan Dobrelya <bdobreli@redhat.com>

paunch/builder/base.py

@@ -78,17 +78,20 @@ class BaseBuilder(object):
                                    container)
                     continue
 
+                c_name = self.runner.discover_container_name(
+                    container, self.config_id) or container
                 cmd = [
                     self.runner.cont_cmd,
                     start_cmd,
                     '--name',
-                    container_name
+                    c_name
                 ]
 
                 self.label_arguments(cmd, container)
-                validations_passed = self.container_run_args(cmd,
-                                                             container,
-                                                             container_name)
+                self.log.debug("Start container {} as {}.".format(container,
+                                                                  c_name))
+                validations_passed = self.container_run_args(
+                    cmd, container, c_name)
             elif action == 'exec':
                 # for exec, the first argument is the fixed named container
                 # used when running the command into the running container.
@@ -102,7 +105,7 @@ class BaseBuilder(object):
                 # Before running the exec, we want to make sure the container
                 # is running.
                 # https://bugs.launchpad.net/bugs/1839559
-                if not self.runner.container_running(c_name):
+                if not c_name or not self.runner.container_running(c_name):
                     msg = ('Failing to apply action exec for '
                            'container: %s' % container)
                     raise RuntimeError(msg)

paunch/runner.py

@@ -170,7 +170,6 @@ class BaseRunner(object):
                 return names[0]
 
         self.log.warning('Did not find container with "%s"' % cmd)
-        return container
 
     def delete_missing_configs(self, config_ids):
         if not config_ids:

paunch/tests/test_runner.py

@@ -142,7 +142,7 @@ class TestBaseRunner(base.TestCase):
         self.mock_execute(popen, '', '', 0)
 
         self.assertEqual(
-            'one',
+            None,
             self.runner.discover_container_name('one', 'foo')
         )
 
@@ -151,7 +151,7 @@ class TestBaseRunner(base.TestCase):
         self.mock_execute(popen, '', 'ouch', 1)
 
         self.assertEqual(
-            'one',
+            None,
             self.runner.discover_container_name('one', 'foo')
         )