Return caching to AppCatalog

Cache Application logo and dynamic_ui markup on local file-system
using `cache.with_cache` decorator. Objects are cached using cPickle
module to allow the function cached by `cache.with_cache` to return
arbitrary objects, not only string or buffer.

Change-Id: Ia0d89b38be1f0776d6e910e3126d89c978db0f10
Implements: blueprint ui-local-cache
Partial-Bug: #1312251

muranodashboard/common/cache.py

@@ -0,0 +1,80 @@
+#    Copyright (c) 2014 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import cPickle as pickle
+import functools
+import logging
+import os
+
+from muranodashboard.environments.consts import CACHE_DIR
+
+
+LOG = logging.getLogger(__name__)
+OBJS_PATH = os.path.join(CACHE_DIR, 'apps')
+
+if not os.path.exists(OBJS_PATH):
+    os.makedirs(OBJS_PATH)
+    LOG.info('Creating apps cache directory located at {dir}'.
+             format(dir=OBJS_PATH))
+
+LOG.info('Using apps cache directory located at {dir}'.
+         format(dir=OBJS_PATH))
+
+
+def _get_entry_path(app_id):
+    head, tail = app_id[:2], app_id[2:]
+    head = os.path.join(OBJS_PATH, head)
+    if not os.path.exists(head):
+        os.mkdir(head)
+    tail = os.path.join(head, tail)
+    if not os.path.exists(tail):
+        os.mkdir(tail)
+    return tail
+
+
+def _load_from_file(file_name):
+    if os.path.isfile(file_name):
+        with open(file_name, 'rb') as f:
+            return pickle.load(f)
+    else:
+        return None
+
+
+def _save_to_file(file_name, content):
+    dir_path = os.path.dirname(file_name)
+    if not os.path.exists(dir_path):
+        os.makedirs(dir_path)
+    with open(file_name, 'wb') as f:
+        pickle.dump(content, f)
+
+
+def with_cache(*dst_parts):
+    def _decorator(func):
+        @functools.wraps(func)
+        def __inner(request, app_id):
+            path = os.path.join(_get_entry_path(app_id), *dst_parts)
+            content = _load_from_file(path)
+            if content is None:
+                content = func(request, app_id)
+                if content:
+                    LOG.debug('Caching value at {0}.'.format(path))
+                    _save_to_file(path, content)
+            else:
+                LOG.debug('Using cached value from {0}.'.format(path))
+
+            return content
+
+        return __inner
+
+    return _decorator