xos/models.py

from core.models.plcorebase import *
from models_decl import VPGWCService_decl
from models_decl import VPGWCTenant_decl

class VPGWCService(VPGWCService_decl):
   class Meta:
        proxy = True 

class VPGWCTenant(VPGWCTenant_decl):
   class Meta:
        proxy = True 

   def __init__(self, *args, **kwargs):
       vpgwcservice = VPGWCService.get_service_objects().all()
       # When the tenant is created the default service in the form is set
       # to be the first created HelloWorldServiceComplete
       if vpgwcservice:
           self._meta.get_field(
                "provider_service").default = vpgwcservice[0].id
       super(VPGWCTenant, self).__init__(*args, **kwargs)

   def save(self, *args, **kwargs):
       # Update the instance that was created for this tenant
       super(VPGWCTenant, self).save(*args, **kwargs)
       model_policy_vpgwctenant(self.pk)   

   def delete(self, *args, **kwargs):
       # Delete the instance that was created for this tenant
       self.cleanup_container()
       super(VPGWCTenant, self).delete(*args, **kwargs)

def model_policy_vpgwctenant(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 = VPGWCTenant.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()