Adds Driver Layer to Image Cache

Fixes LP Bug#879136 - keyerror: 'image' when doing nova image-list
Fixes LP Bug#819936 - New image cache breaks Glance on Windows

This patch refactors the image cache further by adding an
adaptable driver layer to the cache. The existing filesystem-based
driver that depended on python-xattr and conditional fstab support
has been moved to /glance/image_cache/drivers/xattr.py, and a new
default driver is now based on SQLite and has no special requirements.

The image cache now contains a simple interface for pruning the
cache. Instead of the logic being contained in
/glance/image_cache/pruner.py, now the prune logic is self-contained
within the ImageCache.prune() method, with pruning calling the
simple well-defined driver methods of get_least_recently_accessed()
and get_cache_size().

Adds a functional test case for the caching middleware and adds
documentation on how to configure the image cache drivers.

TODO: cache-manage middleware...
TODO: cache management docs

Change-Id: Id7ae73549d6bb39222eb7ac0427b0083fd1af3ec

1 files changed, 4 insertions, 15 deletions

diff --git a/glance/tests/stubs.py b/glance/tests/stubs.py
index 30d084f9f..c2f7f2e6c 100644
--- a/glance/tests/stubs.py
+++ b/glance/tests/stubs.py
@@ -17,27 +17,17 @@
 
 """Stubouts, mocks and fixtures for the test suite"""
 
-import datetime
-import httplib
-import operator
 import os
 import shutil
-import StringIO
-import sys
 
-import stubout
 import webob
 
+from glance.api import v1 as server
+from glance.api.middleware import version_negotiation
 import glance.common.client
 from glance.common import context
 from glance.common import exception
 from glance.registry.api import v1 as rserver
-from glance.api import v1 as server
-from glance.api.middleware import version_negotiation
-import glance.store
-import glance.store.filesystem
-import glance.store.http
-import glance.registry.db.api
 
 
 FAKE_FILESYSTEM_ROOTDIR = os.path.join('/tmp', 'glance-tests')
@@ -199,7 +189,7 @@ def stub_out_registry_and_store_server(stubs):
               fake_image_iter)
 
 
-def stub_out_registry_server(stubs):
+def stub_out_registry_server(stubs, **kwargs):
     """
     Mocks calls to 127.0.0.1 on 9191 for testing so
     that a real Glance Registry server does not need to be up and
@@ -226,8 +216,7 @@ def stub_out_registry_server(stubs):
                 self.req.body = body
 
         def getresponse(self):
-            sql_connection = os.environ.get('GLANCE_SQL_CONNECTION',
-                                            "sqlite:///")
+            sql_connection = kwargs.get('sql_connection', "sqlite:///")
             context_class = 'glance.registry.context.RequestContext'
             options = {'sql_connection': sql_connection, 'verbose': VERBOSE,
                        'debug': DEBUG, 'context_class': context_class}