fix(controller): add source release version

When rolling back releases, the controller would publish a new
release, which meant that the app image would get a version
bump and a new tag on the registry would be created. However,
the tag that was created on the registry was based off the 'latest'
tag. This allows rollbacks to change the source tag to another
version so that the new tag will be based off the release requested.

fixes #1072

controller/api/models.py

@@ -454,7 +454,7 @@ class Meta:
     def __str__(self):
         return "{0}-v{1}".format(self.app.id, self.version)
 
-    def new(self, user, config=None, build=None, summary=None):
+    def new(self, user, config=None, build=None, summary=None, source_version=None):
         """
         Create a new application release using the provided Build and Config
         on behalf of a user.
@@ -465,6 +465,10 @@ def new(self, user, config=None, build=None, summary=None):
             config = self.config
         if not build:
             build = self.build
+        if not source_version:
+            source_version = 'latest'
+        else:
+            source_version = 'v{}'.format(source_version)
         # prepare release tag
         new_version = self.version + 1
         tag = 'v{}'.format(new_version)
@@ -475,7 +479,10 @@ def new(self, user, config=None, build=None, summary=None):
             build=build, version=new_version, image=image, summary=summary)
         # publish release to registry as new docker image
         repository_path = self.app.id
-        publish_release(repository_path, config.values, tag)
+        publish_release(repository_path,
+                        config.values,
+                        tag,
+                        source_tag=source_version)
         return release
 
     def previous(self):

controller/api/views.py

@@ -424,7 +424,11 @@ def rollback(self, request, *args, **kwargs):
         summary = "{} rolled back to v{}".format(request.user, version)
         prev = app.release_set.get(version=version)
         new_release = release.new(
-            request.user, build=prev.build, config=prev.config, summary=summary)
+            request.user,
+            build=prev.build,
+            config=prev.config,
+            summary=summary,
+            source_version=version)
         app.deploy(new_release)
         msg = "Rolled back to v{}".format(version)
         return Response(msg, status=status.HTTP_201_CREATED)

controller/registry/mock.py

@@ -1,5 +1,5 @@
 
-def publish_release(repository_path, config, tag):
+def publish_release(repository_path, config, tag, source_tag='latest'):
     """
     Publish a new release as a Docker image
 

controller/registry/private.py

@@ -9,23 +9,30 @@
 from django.conf import settings
 
 
-def publish_release(repository_path, config, tag):
+def publish_release(repository_path, config, tag, source_tag='latest'):
     """
     Publish a new release as a Docker image
 
     Given a source repository path, a dictionary of environment variables
     and a target tag, create a new lightweight Docker image on the registry.
 
+    source_tag is the name of the previous older tag that this image should
+    be a child of. In most cases, this should be 'latest', but for rollbacks
+    this should be an older tag.
+
     For example, publish_release('gabrtv/myapp', {'ENVVAR': 'values'}, 'v23')
     results in a new Docker image at: <registry_url>/gabrtv/myapp:v23
     which contains the new configuration as ENV entries.
     """
     try:
-        image_id = _get_tag(repository_path, 'latest')
+        image_id = _get_tag(repository_path, source_tag)
     except RuntimeError:
-        # no image exists yet, so let's build one!
-        _put_first_image(repository_path)
-        image_id = _get_tag(repository_path, 'latest')
+        if source_tag == 'latest':
+            # no image exists yet, so let's build one!
+            _put_first_image(repository_path)
+            image_id = _get_tag(repository_path, 'latest')
+        else:
+            raise
     image = _get_image(image_id)
     # construct the new image
     image['parent'] = image['id']