fix(controller): give processes unique counters

Previously, when a container was created through App.scale(),
it would give the container a number based off the highest
container number amongst all containers available for the application.
This has been changed to give the container a number based off the
highest container number amongst all containers with the same process
type.

fixes #769

Author: Matthew Fisher

controller/api/models.py

@@ -15,6 +15,7 @@
 from django.conf import settings
 from django.contrib.auth.models import User
 from django.db import models
+from django.db.models import Max
 from django.db.models.signals import post_delete
 from django.db.models.signals import post_save
 from django.utils.encoding import python_2_unicode_compatible
@@ -138,16 +139,16 @@ def scale(self, **kwargs):
         """Scale containers up or down to match requested."""
         requested_containers = self.structure.copy()
         release = self.release_set.latest()
-        # increment new container nums off the most recent container
-        all_containers = self.container_set.all().order_by('-created')
-        container_num = 1 if not all_containers else all_containers[0].num + 1
         msg = 'Containers scaled ' + ' '.join(
             "{}={}".format(k, v) for k, v in requested_containers.items())
         # iterate and scale by container type (web, worker, etc)
         changed = False
         to_add, to_remove = [], []
         for container_type in requested_containers.keys():
             containers = list(self.container_set.filter(type=container_type).order_by('created'))
+            # increment new container nums off the most recent container
+            results = self.container_set.filter(type=container_type).aggregate(Max('num'))
+            container_num = results.get('num__max') or 0 + 1
             requested = requested_containers.pop(container_type)
             diff = requested - len(containers)
             if diff == 0:

controller/api/tests/test_container.py

@@ -151,6 +151,7 @@ def test_container_api(self):
         response = self.client.get(url)
         self.assertEqual(response.status_code, 200)
         self.assertEqual(len(response.data['results']), 3)
+        self.assertEqual(max(c['num'] for c in response.data['results']), 2)
         url = "/api/apps/{app_id}".format(**locals())
         response = self.client.get(url)
         self.assertEqual(response.status_code, 200)