Add publisher infrastructure

Adds plumbing for "publishers."  Publishers are strategy classes
responsible for preparing images for distribution.

An example publisher should be a BitTorrent publisher that took the
image binary, generated a torrent file from it, and started an initial
seeder process.

The default publisher is nop.Publisher, which takes no action.

Change-Id: I8fd952270aaf4fc6962dafc1f287aca0cd0c9828

cachemonkey/cacher.py

@@ -50,7 +50,6 @@ class Cacher(object):
             CONF.cachemonkey.fetcher_class)
 
         self.discoverer = discover.ComputeDiscoverer()
-        self.images = []
 
     def cache(self):
         self.images = []
@@ -58,8 +57,8 @@ class Cacher(object):
 
         for image in images:
             filename = self._get(image)
-            image = {'meta': image, 'filename': filename}
-            self.images.append(image)
+
+            self.publisher.publish(image, filename)
 
             # HACK(belliott) - just process first image for testing
             break

cachemonkey/publisher/nop.py

@@ -0,0 +1,27 @@
+# Copyright 2014 Rackspace Hosting
+# All Rights Reserved.
+#
+#    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.
+
+from cachemonkey.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
+
+
+class Publisher(object):
+    """A do-nothing publisher.  Use when no special work is required to
+    prepare an image for distribution to computes.
+    """
+
+    def publish(self, image, filename):
+        pass

cachemonkey/tests/publisher/test_nop.py

@@ -0,0 +1,27 @@
+# Copyright 2014 Rackspace Hosting
+# All Rights Reserved.
+#
+#    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.
+
+from oslotest import base
+
+from cachemonkey.publisher import nop
+
+
+class NopPublisherTestCase(base.BaseTestCase):
+
+    def test_nop(self):
+        publisher = nop.Publisher()
+        image = {'id': '1234'}
+        filename = '/abc/def'
+        publisher.publish(image, filename)