Add the "None" datasource

The None datasource is the last resort fallback datasource.  It is
identifiable by a property 'is_disconnected' that indicates that the
datasource used is "not connected to a datasource".

This will allow any thing that needs to run to still run in the absense
of a DataSource.

Also, we add a logging of the datasource found in final_message, and
a warning if the None datasource is found.

ChangeLog

@@ -1,4 +1,6 @@
 0.7.0:
+ - add the 'None' datasource (LP: #906669), which will allow jobs
+   to run even if there is no "real" datasource found.
  - write ssh authorized keys to console, ssh_authkey_fingerprints
    config module [Joshua Harlow] (LP: #1010582)
  - Added RHEVm and vSphere support as source AltCloud [Joseph VLcek]

cloudinit/config/cc_final_message.py

@@ -28,7 +28,7 @@ frequency = PER_ALWAYS
 
 # Cheetah formated default message
 FINAL_MESSAGE_DEF = ("Cloud-init v. ${version} finished at ${timestamp}."
-                     " Up ${uptime} seconds.")
+                     " Datasource ${datasource}.  Up ${uptime} seconds")
 
 
 def handle(_name, cfg, cloud, log, args):
@@ -51,6 +51,7 @@ def handle(_name, cfg, cloud, log, args):
             'uptime': uptime,
             'timestamp': ts,
             'version': cver,
+            'datasource': str(cloud.datasource),
         }
         util.multi_log("%s\n" % (templater.render_string(msg_in, subs)),
                        console=False, stderr=True)
@@ -63,3 +64,6 @@ def handle(_name, cfg, cloud, log, args):
         util.write_file(boot_fin_fn, contents)
     except:
         util.logexc(log, "Failed to write boot finished file %s", boot_fin_fn)
+
+    if cloud.datasource.is_disconnected:
+        log.warn("Used fallback datasource")

cloudinit/settings.py

@@ -35,7 +35,9 @@ CFG_BUILTIN = {
         'OVF',
         'MAAS',
         'Ec2',
-        'CloudStack'
+        'CloudStack',
+        # At the end to act as a 'catch' when none of the above work...
+        'None',
     ],
     'def_log_file': '/var/log/cloud-init.log',
     'log_cfgs': [],

cloudinit/sources/DataSourceNone.py

@@ -0,0 +1,63 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    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 cloudinit import log as logging
+from cloudinit import sources
+from cloudinit import util
+
+LOG = logging.getLogger(__name__)
+
+
+class DataSourceNone(sources.DataSource):
+    def __init__(self, sys_cfg, distro, paths, ud_proc=None):
+        sources.DataSource.__init__(self, sys_cfg, distro, paths, ud_proc)
+        self.userdata = {}
+        self.metadata = {}
+        self.userdata_raw = ''
+
+    def get_data(self):
+        # If the datasource config has any provided 'fallback'
+        # userdata or metadata, use it...
+        if 'userdata' in self.ds_cfg:
+            self.userdata = self.ds_cfg['userdata']
+            self.userdata_raw = util.yaml_dumps(self.userdata)
+        if 'metadata' in self.ds_cfg:
+            self.metadata = self.ds_cfg['metadata']
+        return True
+
+    def get_instance_id(self):
+        return 'iid-datasource-none'
+
+    def __str__(self):
+        return util.obj_name(self)
+
+    @property
+    def is_disconnected(self):
+        return True
+
+
+# Used to match classes to dependencies
+datasources = [
+  (DataSourceNone, (sources.DEP_FILESYSTEM, sources.DEP_NETWORK)),
+  (DataSourceNone, []),
+]
+
+
+# Return a list of data sources that match this set of dependencies
+def get_datasource_list(depends):
+    return sources.list_from_depends(depends, datasources)

cloudinit/sources/__init__.py

@@ -65,6 +65,10 @@ class DataSource(object):
             self.userdata = self.ud_proc.process(raw_data)
         return self.userdata
 
+    @property
+    def is_disconnected(self):
+        return False
+
     def get_userdata_raw(self):
         return self.userdata_raw