Datasources: Formalize DataSource get_data and related properties.

Each DataSource subclass must define its own get_data method. This branch
formalizes our DataSource class to require that subclasses define an
explicit dsname for sourcing cloud-config datasource configuration.
Subclasses must also override the _get_data method or a
NotImplementedError is raised.

The branch also writes /run/cloud-init/instance-data.json. This file
contains all meta-data, user-data and vendor-data and a standardized set
of metadata keys in a json blob which other utilities with root-access
could make use of. Because some meta-data or user-data is potentially
sensitive the file is only readable by root.

Generally most metadata content types should be json serializable. If
specific keys or values are not serializable, those specific values will
be base64encoded and the key path will be listed under the top-level key
'base64-encoded-keys' in instance-data.json. If json writing fails due to
other TypeErrors or UnicodeDecodeErrors, a warning log will be emitted to
/var/log/cloud-init.log and no instance-data.json will be created.

1 files changed, 9 insertions, 3 deletions

diff --git a/cloudinit/sources/DataSourceEc2.py b/cloudinit/sources/DataSourceEc2.py
index 7bbbfb63..e5c88334 100644
--- a/cloudinit/sources/DataSourceEc2.py
+++ b/cloudinit/sources/DataSourceEc2.py
@@ -31,6 +31,7 @@ _unset = "_unset"
 
 
 class Platforms(object):
+    # TODO Rename and move to cloudinit.cloud.CloudNames
     ALIYUN = "AliYun"
     AWS = "AWS"
     BRIGHTBOX = "Brightbox"
@@ -45,6 +46,7 @@ class Platforms(object):
 
 class DataSourceEc2(sources.DataSource):
 
+    dsname = 'Ec2'
     # Default metadata urls that will be used if none are provided
     # They will be checked for 'resolveability' and some of the
     # following may be discarded if they do not resolve
@@ -68,11 +70,15 @@ class DataSourceEc2(sources.DataSource):
     _fallback_interface = None
 
     def __init__(self, sys_cfg, distro, paths):
-        sources.DataSource.__init__(self, sys_cfg, distro, paths)
+        super(DataSourceEc2, self).__init__(sys_cfg, distro, paths)
         self.metadata_address = None
         self.seed_dir = os.path.join(paths.seed_dir, "ec2")
 
-    def get_data(self):
+    def _get_cloud_name(self):
+        """Return the cloud name as identified during _get_data."""
+        return self.cloud_platform
+
+    def _get_data(self):
         seed_ret = {}
         if util.read_optional_seed(seed_ret, base=(self.seed_dir + "/")):
             self.userdata_raw = seed_ret['user-data']
@@ -274,7 +280,7 @@ class DataSourceEc2(sources.DataSource):
         return None
 
     @property
-    def cloud_platform(self):
+    def cloud_platform(self):  # TODO rename cloud_name
         if self._cloud_platform is None:
             self._cloud_platform = identify_platform()
         return self._cloud_platform