fix(tests): close db connections during threaded execution

This appears to resolve https://code.djangoproject.com/ticket/22420
allowing us to get test coverage for threads executed within
TransactionTestCases.

Author: Gabriel Monroy

controller/api/models.py

@@ -14,7 +14,7 @@
 from celery.canvas import group
 from django.conf import settings
 from django.contrib.auth.models import User
-from django.db import models
+from django.db import models, connections
 from django.db.models import Max
 from django.db.models.signals import post_delete
 from django.db.models.signals import post_save
@@ -36,6 +36,20 @@ def log_event(app, msg, level=logging.INFO):
     logger.log(level, msg)
 
 
+def close_db_connections(func, *args, **kwargs):
+    """
+    Decorator to close db connections during threaded execution
+
+    Note this is necessary to work around:
+    https://code.djangoproject.com/ticket/22420
+    """
+    def _inner(*args, **kwargs):
+        func(*args, **kwargs)
+        for conn in connections.all():
+            conn.close()
+    return _inner
+
+
 class AuditedModel(models.Model):
     """Add created and updated fields to a model."""
 
@@ -290,18 +304,21 @@ def _get_command(self):
 
     _command = property(_get_command)
 
+    @close_db_connections
     @transition(field=state, source=INITIALIZED, target=CREATED)
     def create(self):
         image = self.release.image
         c_type = self.type
         self._scheduler.create(self._job_id, image, self._command.format(**locals()))
 
+    @close_db_connections
     @transition(field=state,
                 source=[CREATED, UP, DOWN],
                 target=UP, crashed=DOWN)
     def start(self):
         self._scheduler.start(self._job_id)
 
+    @close_db_connections
     @transition(field=state,
                 source=[INITIALIZED, CREATED, UP, DOWN],
                 target=UP,
@@ -320,10 +337,12 @@ def deploy(self, release):
         # destroy old container
         self._scheduler.destroy(old_job_id)
 
+    @close_db_connections
     @transition(field=state, source=UP, target=DOWN)
     def stop(self):
         self._scheduler.stop(self._job_id)
 
+    @close_db_connections
     @transition(field=state,
                 source=[INITIALIZED, CREATED, UP, DOWN],
                 target=DESTROYED)