vm: refactor activity code construction

circle/common/models.py

@@ -214,6 +214,14 @@ class ActivityModel(TimeStampedModel):
 
         self.result_data = None if value is None else value.to_dict()
 
+    @classmethod
+    def construct_activity_code(cls, code_suffix, sub_suffix=None):
+        code = join_activity_code(cls.ACTIVITY_CODE_BASE, code_suffix)
+        if sub_suffix:
+            return join_activity_code(code, sub_suffix)
+        else:
+            return code
+
 
 @celery.task()
 def compute_cached(method, instance, memcached_seconds,

circle/vm/models/activity.py

@@ -99,7 +99,7 @@ class InstanceActivity(ActivityModel):
         if concurrency_check and active_activities.exists():
             raise ActivityInProgressError.create(active_activities[0])
 
-        activity_code = join_activity_code(cls.ACTIVITY_CODE_BASE, code_suffix)
+        activity_code = cls.construct_activity_code(code_suffix)
         act = cls(activity_code=activity_code, instance=instance, parent=None,
                   resultant_state=resultant_state, started=timezone.now(),
                   readable_name_data=readable_name.to_dict(),