Rethinking file system access

Made provision to load reserved_stores if it is specified in
glance. Added keywrod argument to 'register_store_opts' and
'create_multi_stores' method.

Change-Id: I965df1883639bfd5c900d2902884153d48988f6e
Partial-Implements: blueprint rethinking-filesystem-access

glance_store/multi_backend.py

@@ -46,6 +46,7 @@ Related Options:
 ]
 
 _STORE_CFG_GROUP = 'glance_store'
+_RESERVED_STORES = {}
 
 
 def _list_config_opts():
@@ -88,12 +89,15 @@ def _list_driver_opts():
     return driver_opts
 
 
-def register_store_opts(conf):
+def register_store_opts(conf, reserved_stores=None):
     LOG.debug("Registering options for group %s", _STORE_CFG_GROUP)
     conf.register_opts(_STORE_OPTS, group=_STORE_CFG_GROUP)
 
     driver_opts = _list_driver_opts()
     enabled_backends = conf.enabled_backends
+    if reserved_stores:
+        enabled_backends.update(reserved_stores)
+
     for backend in enabled_backends:
         for opt_list in driver_opts:
             if enabled_backends[backend] not in opt_list:
@@ -122,8 +126,12 @@ def _load_multi_store(conf, store_entry,
                     "driver will be disabled", dict(driver=str([driver, e])))
 
 
-def _load_multi_stores(conf):
+def _load_multi_stores(conf, reserved_stores=None):
     enabled_backends = conf.enabled_backends
+    if reserved_stores:
+        enabled_backends.update(reserved_stores)
+        _RESERVED_STORES.update(reserved_stores)
+
     for backend, store_entry in enabled_backends.items():
         try:
             # FIXME(flaper87): Don't hide BadStoreConfiguration
@@ -141,12 +149,13 @@ def _load_multi_stores(conf):
             continue
 
 
-def create_multi_stores(conf=CONF):
+def create_multi_stores(conf=CONF, reserved_stores=None):
     """Registers all store modules and all schemes from the given config."""
     store_count = 0
     scheme_map = {}
     for (store_entry, store_instance,
-         store_identifier) in _load_multi_stores(conf):
+         store_identifier) in _load_multi_stores(
+            conf, reserved_stores=reserved_stores):
         try:
             schemes = store_instance.get_schemes()
             store_instance.configure(re_raise_bsc=False)
@@ -197,6 +206,8 @@ def get_store_from_store_identifier(store_identifier):
     """
     scheme_map = {}
     enabled_backends = CONF.enabled_backends
+    enabled_backends.update(_RESERVED_STORES)
+
     try:
         scheme = enabled_backends[store_identifier]
     except KeyError:

glance_store/tests/unit/test_store_base.py

@@ -15,8 +15,12 @@
 
 import mock
 
+from oslo_config import cfg
+
 import glance_store as store
 from glance_store import backend
+from glance_store import location
+from glance_store import multi_backend
 from glance_store.tests import base
 
 
@@ -38,3 +42,48 @@ class TestStoreBase(base.StoreBaseTest):
                 "could not be configured correctly. Reason: Specify "
                 "at least 'filesystem_store_datadir' or "
                 "'filesystem_store_datadirs' option Disabling add method.")
+
+
+class TestMultiStoreBase(base.MultiStoreBaseTest):
+    _CONF = multi_backend.CONF
+
+    def setUp(self):
+        super(TestMultiStoreBase, self).setUp()
+        enabled_backends = {
+            "fast": "file",
+            "cheap": "file",
+        }
+
+        self.reserved_stores = {
+            'consuming_service_reserved_store': 'file'
+        }
+
+        self.conf = self._CONF
+        self.conf(args=[])
+        self.conf.register_opt(cfg.DictOpt('enabled_backends'))
+        self.config(enabled_backends=enabled_backends)
+
+        store.register_store_opts(self.conf,
+                                  reserved_stores=self.reserved_stores)
+        self.config(default_backend='file1', group='glance_store')
+
+        # Ensure stores + locations cleared
+        location.SCHEME_TO_CLS_BACKEND_MAP = {}
+
+        store.create_multi_stores(self.conf,
+                                  reserved_stores=self.reserved_stores)
+        self.addCleanup(setattr, location, 'SCHEME_TO_CLS_BACKEND_MAP',
+                        dict())
+        self.addCleanup(self.conf.reset)
+
+    def test_reserved_stores_loaded(self):
+        # assert global map has reserved stores registered
+        store = multi_backend.get_store_from_store_identifier(
+            'consuming_service_reserved_store')
+
+        self.assertIsNotNone(store)
+        self.assertEqual(self.reserved_stores, multi_backend._RESERVED_STORES)
+        # verify that store config group in conf file is same as
+        # reserved store name
+        self.assertEqual('consuming_service_reserved_store',
+                         store.backend_group)

releasenotes/notes/rethinking-filesystem-access-5ab872fd0c0d27db.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Added keyword argument to ``register_store_opts`` and
+    ``create_multi_stores`` calls to configure reserved stores by the consuming
+    service. This feature will allow a mix of operator-configured stores via
+    enabled_backends configuration option set in the [glance_store] section
+    of the consuming service's configuration file, and stores that are
+    reserved for use by the consuming service.