[MCORD-183] Fix instance creation from UI

Change-Id: I4f5db09aa17e96819f797a7bf68706ec7f683d43
diff --git a/xos/models.py b/xos/models.py
new file mode 100644
index 0000000..c465d96
--- /dev/null
+++ b/xos/models.py
@@ -0,0 +1,41 @@
+from core.models.plcorebase import *
+from models_decl import VSGWService_decl
+from models_decl import VSGWTenant_decl
+
+class VSGWService(VSGWService_decl):
+   class Meta:
+        proxy = True 
+
+class VSGWTenant(VSGWTenant_decl):
+   class Meta:
+        proxy = True 
+        
+   def __init__(self, *args, **kwargs):
+       vsgwservice = VSGWService.get_service_objects().all()
+       if vsgwservice:
+           self._meta.get_field(
+                   "provider_service").default = vsgwservice[0].id
+       super(VSGWTenant, self).__init__(*args, **kwargs)
+
+   def save(self, *args, **kwargs):
+       super(VSGWTenant, self).save(*args, **kwargs)
+       # This call needs to happen so that an instance is created for this
+       # tenant is created in the slice. One instance is created per tenant.
+       model_policy_vsgwtenant(self.pk)
+
+   def delete(self, *args, **kwargs):
+       # Delete the instance that was created for this tenant
+       self.cleanup_container()
+       super(VSGWTenant, self).delete(*args, **kwargs)
+
+def model_policy_vsgwtenant(pk):
+    # This section of code is atomic to prevent race conditions
+    with transaction.atomic():
+        # We find all of the tenants that are waiting to update
+        tenant = VSGWTenant.objects.select_for_update().filter(pk=pk)
+        if not tenant:
+            return
+        # Since this code is atomic it is safe to always use the first tenant
+        tenant = tenant[0]
+        tenant.manage_container()
+