support launch index specific user-data

EC2 and openstack provide 'launch_index' in their metadata. This allows
the user to specify cloud-config or multipart mime data that includes the
'Launch-Index' header.

If launch index is available in the metadata service, then:
 * any part that contains a launch index other than the current launch-index
   of this instance will be ignored.
 * any part that does not contain a launch index will be considered as
   for this instance.

If there is no such header, or launch_index is not available in the metadata
service, then no such filtering will be done.

LP: #1023177

2 files changed, 31 insertions, 3 deletions

diff --git a/cloudinit/sources/DataSourceEc2.py b/cloudinit/sources/DataSourceEc2.py
index 7e845571..c7ad6d54 100644
--- a/cloudinit/sources/DataSourceEc2.py
+++ b/cloudinit/sources/DataSourceEc2.py
@@ -77,6 +77,12 @@ class DataSourceEc2(sources.DataSource):
                         self.metadata_address)
             return False
 
+    @property
+    def launch_index(self):
+        if not self.metadata:
+            return None
+        return self.metadata.get('ami-launch-index')
+
     def get_instance_id(self):
         return self.metadata['instance-id']
 
diff --git a/cloudinit/sources/__init__.py b/cloudinit/sources/__init__.py
index 4719d254..3f611d44 100644
--- a/cloudinit/sources/__init__.py
+++ b/cloudinit/sources/__init__.py
@@ -20,6 +20,8 @@
 #    You should have received a copy of the GNU General Public License
 #    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+from email.mime.multipart import MIMEMultipart
+
 import abc
 
 from cloudinit import importer
@@ -27,6 +29,8 @@ from cloudinit import log as logging
 from cloudinit import user_data as ud
 from cloudinit import util
 
+from cloudinit.filters import launch_index
+
 DEP_FILESYSTEM = "FILESYSTEM"
 DEP_NETWORK = "NETWORK"
 DS_PREFIX = 'DataSource'
@@ -59,13 +63,31 @@ class DataSource(object):
         else:
             self.ud_proc = ud_proc
 
-    def get_userdata(self):
+    def get_userdata(self, apply_filter=False):
         if self.userdata is None:
-            raw_data = self.get_userdata_raw()
-            self.userdata = self.ud_proc.process(raw_data)
+            self.userdata = self.ud_proc.process(self.get_userdata_raw())
+        if apply_filter:
+            return self._filter_userdata(self.userdata)
         return self.userdata
 
     @property
+    def launch_index(self):
+        if not self.metadata:
+            return None
+        if 'launch-index' in self.metadata:
+            return self.metadata['launch-index']
+        return None
+
+    def _filter_userdata(self, processed_ud):
+        filters = [
+            launch_index.Filter(util.safe_int(self.launch_index)),
+        ]
+        new_ud = processed_ud
+        for f in filters:
+            new_ud = f.apply(new_ud)
+        return new_ud
+
+    @property
     def is_disconnected(self):
         return False