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

1 files changed, 7 insertions, 4 deletions

diff --git a/cloudinit/util.py b/cloudinit/util.py
index 6872cc31..33da73eb 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -1285,12 +1285,15 @@ def ensure_file(path, mode=0644):
     write_file(path, content='', omode="ab", mode=mode)
 
 
-def chmod(path, mode):
-    real_mode = None
+def safe_int(possible_int):
     try:
-        real_mode = int(mode)
+        return int(possible_int)
     except (ValueError, TypeError):
-        pass
+        return None
+
+
+def chmod(path, mode):
+    real_mode = safe_int(mode)
     if path and real_mode:
         with SeLinuxGuard(path):
             os.chmod(path, real_mode)