Added ServiceUnvailable error handling for the case when we have no connection to OpenNebula.

opennebula_api/views.py

@@ -12,6 +12,12 @@ from guardian.mixins import PermissionRequiredMixin
 from .serializers import VirtualMachineTemplateSerializer, \
                          VirtualMachineSerializer
 from .models import OpenNebulaManager
+from rest_framework.exceptions import APIException
+
+class ServiceUnavailable(APIException):
+    status_code = 503
+    default_detail = 'Service temporarily unavailable, try again later.'
+    default_code = 'service_unavailable'
 
 
 class TemplateCreateView(generics.ListCreateAPIView):
@@ -37,7 +43,14 @@ class TemplateDetailsView(generics.RetrieveUpdateDestroyAPIView):
 
     def get_queryset(self):
         manager = OpenNebulaManager()
-        return manager.get_templates()
+        # We may have ConnectionRefusedError if we don't have a 
+        # connection to OpenNebula. For now, we raise ServiceUnavailable
+        try:
+            templates = manager.get_templates()
+        except ConnectionRefusedError:
+            raise ServiceUnavailable            
+        
+        return templates
 
 class VmCreateView(generics.ListCreateAPIView):
     """This class handles the GET and POST requests."""
@@ -48,7 +61,13 @@ class VmCreateView(generics.ListCreateAPIView):
         owner = self.request.user
         manager = OpenNebulaManager(email=owner.email,
                                     password=owner.password)
-        return manager.get_vms()
+        # We may have ConnectionRefusedError if we don't have a 
+        # connection to OpenNebula. For now, we raise ServiceUnavailable
+        try:
+            vms = manager.get_vms()
+        except ConnectionRefusedError:
+            raise ServiceUnavailable
+        return vms
 
     def perform_create(self, serializer):
         """Save the post data when creating a new template."""
@@ -64,17 +83,34 @@ class VmDetailsView(generics.RetrieveUpdateDestroyAPIView):
         owner = self.request.user
         manager = OpenNebulaManager(email=owner.email,
                                     password=owner.password)
-        return manager.get_vms()
+        # We may have ConnectionRefusedError if we don't have a 
+        # connection to OpenNebula. For now, we raise ServiceUnavailable
+        try:
+            vms = manager.get_vms()
+        except ConnectionRefusedError:
+            raise ServiceUnavailable
+        return vms
 
     def get_object(self):
         owner = self.request.user
         manager = OpenNebulaManager(email=owner.email,
                                     password=owner.password)
-        return manager.get_vm(self.kwargs.get('pk'))
+        # We may have ConnectionRefusedError if we don't have a 
+        # connection to OpenNebula. For now, we raise ServiceUnavailable
+        try:
+            vm = manager.get_vm(self.kwargs.get('pk'))
+        except ConnectionRefusedError:
+            raise ServiceUnavailable
+        return vm                                    
 
     def perform_destroy(self, instance):
         owner = self.request.user
         manager = OpenNebulaManager(email=owner.email,
                                     password=owner.password)
+        # We may have ConnectionRefusedError if we don't have a 
+        # connection to OpenNebula. For now, we raise ServiceUnavailable
+        try:
             manager.delete_vm(instance.id)
+        except ConnectionRefusedError:
+            raise ServiceUnavailable