Mark http store read-only in discovery call

Made changes to discovery store to show 'http'
store as 'read-only' if it is configured under
'enabled_backends' cofiguration option.

Change-Id: If5d292bbb4cef1bd21a7e6cd4ef343a767eb91a4

api-ref/source/v2/discovery-parameters.yaml

@@ -6,6 +6,7 @@ stores:
     - ``id``
     - ``description``
     - ``default``
+    - ``read-only``
   in: body
   required: true
   type: array

api-ref/source/v2/samples/stores-list-response.json

@@ -12,6 +12,11 @@
         {
             "id":"cheap",
             "description": "Less expensive rbd store"
+        },
+        {
+            "id":"read_only_store",
+            "description": "Read only http store",
+            "read-only": true
         }
     ]
-}
+}

doc/source/admin/multistores.rst

@@ -50,17 +50,24 @@ operators to enable multiple stores support.
     represents the identifier for the store and value will be the type
     of the store. Valid values are one of ``file``, ``http``, ``rbd``,
     ``swift``, ``cinder``, ``sheepdog`` or ``vmware``. In order to have
-    multiple stores operator can specify multiple key:value separated by comma.
+    multiple stores operator can specify multiple key:value separated by
+    comma.
+
+    Due to the special read only nature and characteristics of the
+    http store type, we do not encourage nor support configuring
+    multiple instances of the http type store even though it's
+    possible.
+
+    The http store type is always treated by Glance as a read-only
+    store.  This is indicated in the response to the ``/v2/stores/info``
+    call, where an http type store will have the attribute ``read-only:
+    True`` in addition to the usual ``id`` and ``description`` fields.
 
     .. code-block:: ini
 
          [DEFAULT]
          enabled_backends = fast:rbd, cheap:rbd, shared:file, reliable:file
 
-    .. note:: Due to the special read only nature and characteristics of the
-              http store we do not encourage nor support configuring multiple
-              instances of http store even though it's possible.
-
 * in the ``[glance_store]`` options group:
 
   * ``default_backend`` must be set to one of the identifier which are defined

glance/api/v2/discovery.py

@@ -53,6 +53,9 @@ class InfoController(object):
                 stores['description'] = description
             if backend == CONF.glance_store.default_backend:
                 stores['default'] = "true"
+            # Check if http store is configured then mark it as read-only
+            if enabled_backends[backend] == 'http':
+                stores['read-only'] = "true"
             backends.append(stores)
 
         return {'stores': backends}

glance/tests/unit/base.py

@@ -72,7 +72,8 @@ class MultiStoreClearingUnitTest(test_utils.BaseTestCase):
         :param passing_config: making store driver passes basic configurations.
         :returns: the number of how many store drivers been loaded.
         """
-        self.config(enabled_backends={'file1': 'file', 'ceph1': 'rbd'})
+        self.config(enabled_backends={'file1': 'file', 'ceph1': 'rbd',
+                                      'readonly_store': 'http'})
         store.register_store_opts(CONF)
 
         self.config(default_backend='file1',

glance/tests/unit/v2/test_discovery_stores.py

@@ -39,10 +39,23 @@ class TestInfoControllers(base.MultiStoreClearingUnitTest):
                           req)
 
     def test_get_stores(self):
-        available_stores = ['ceph1', 'file1']
+        available_stores = ['ceph1', 'file1', 'readonly_store']
         req = unit_test_utils.get_fake_request()
         output = self.controller.get_stores(req)
         self.assertIn('stores', output)
         for stores in output['stores']:
             self.assertIn('id', stores)
             self.assertIn(stores['id'], available_stores)
+
+    def test_get_stores_read_only_store(self):
+        available_stores = ['ceph1', 'file1', 'readonly_store']
+        req = unit_test_utils.get_fake_request()
+        output = self.controller.get_stores(req)
+        self.assertIn('stores', output)
+        for stores in output['stores']:
+            self.assertIn('id', stores)
+            self.assertIn(stores['id'], available_stores)
+            if stores['id'] == 'readonly_store':
+                self.assertTrue(stores['read-only'])
+            else:
+                self.assertIsNone(stores.get('read-only'))