From 62be9ae7890ee0cad38d541f0c0efdfaa3f23e09 Mon Sep 17 00:00:00 2001
From: "M.Ravi" <mondi.ravi@gmail.com>
Date: Sun, 14 May 2017 17:39:10 +0530
Subject: [PATCH] Added ServiceUnvailable error handling for the case when we
 have no connection to OpenNebula.

---
 opennebula_api/views.py | 46 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 5 deletions(-)

diff --git a/opennebula_api/views.py b/opennebula_api/views.py
index 170c9716..d982f7bb 100644
--- a/opennebula_api/views.py
+++ b/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)
-        manager.delete_vm(instance.id)
+        # 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