feat(client): check server version

If the client sends a X-Deis-Version header to the server, a django
middleware class will validate and ensure that the versions are the
same. If they are not, the request is rejected, and a HttpResponse
object is returned with the client and server versions displayed.

Author: Matthew Fisher

client/deis.py

@@ -362,18 +362,25 @@ def __init__(self):
         self._session = Session()
         self._settings = Settings()
 
-    def _dispatch(self, method, path, body=None,
-                  headers={'content-type': 'application/json'}, **kwargs):
+    def _dispatch(self, method, path, body=None, **kwargs):
         """
         Dispatch an API request to the active Deis controller
         """
+        headers = {
+            'content-type': 'application/json',
+            'X-Deis-Version': __version__.rsplit('.', 1)[0],
+        }
         func = getattr(self._session, method.lower())
         controller = self._settings['controller']
         if not controller:
             raise EnvironmentError(
                 'No active controller. Use `deis login` or `deis register` to get started.')
         url = urlparse.urljoin(controller, path, **kwargs)
         response = func(url, data=body, headers=headers)
+        # check for errors
+        if response.json().get('error') is not None:
+            print(response.json()['error'])
+            sys.exit(1)
         return response
 
     def apps(self, args):

controller/api/middleware.py

@@ -0,0 +1,25 @@
+import json
+
+from django.http import HttpResponse
+
+from deis import __version__
+
+
+class VersionMiddleware:
+
+    def process_request(self, request):
+        # server and client version must match "x.y"
+        server_version = __version__.rsplit('.', 1)[0]
+        try:
+            if request.META['HTTP_X_DEIS_VERSION'] != server_version:
+                message = {
+                    'error': 'Client and server versions do not match.\n' +
+                    'Client version: {}\n'.format(server_version) +
+                    'Server version: {}'.format(request.META['HTTP_X_DEIS_VERSION'])
+                }
+                return HttpResponse(
+                    json.dumps(message),
+                    content_type='application/json'
+                )
+        except KeyError:
+            pass

controller/deis/settings.py

@@ -108,6 +108,7 @@
     'django.middleware.csrf.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
+    'api.middleware.VersionMiddleware',
     # Uncomment the next line for simple clickjacking protection:
     # 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 )