rework of DataSource loading.

The DataSources that are loaded are now controlled entirely via
configuration file of 'datasource_list', like:
   datasource_list: [ "NoCloud", "OVF", "Ec2" ]

Each item in that list is a "DataSourceCollection".  for each item
in the list, cloudinit will attempt to load:
  cloudinit.DataSource<item>
and, failing that,
  DataSource<item>

The module is required to have a method named 'get_datasource_list'
in it that takes a single list of "dependencies" and returns
a list of python classes inside the collection that can run needing
only those dependencies.

The dependencies are defines in DataSource.py. Currently:
  DEP_FILESYSTEM = "FILESYSTEM"
  DEP_NETWORK = "NETWORK"

When 'get_datasource_list' is called for the DataSourceOVF module with
[DEP_FILESYSTEM], then DataSourceOVF returns a single item list with a
reference to the 'DataSourceOVF' class.

When 'get_datasource_list' is called for the DataSourceOVF module with
[DEP_FILESYSTEM, DEP_NETWORK], it will return a single item list
with a reference to 'DataSourceOVFNet'.

cloudinit will then instanciate the class and call its 'get_data' method.
if the get_data method returns 'True', then it selects this class as the
selected Datasource.

1 files changed, 15 insertions, 8 deletions

diff --git a/cloudinit/DataSourceOVF.py b/cloudinit/DataSourceOVF.py
index 3fba878b..31d0c407 100644
--- a/cloudinit/DataSourceOVF.py
+++ b/cloudinit/DataSourceOVF.py
@@ -18,7 +18,7 @@
 
 import DataSource
 
-import cloudinit
+from cloudinit import seeddir
 import cloudinit.util as util
 import sys
 import os.path
@@ -33,16 +33,13 @@ import subprocess
 
 class DataSourceOVF(DataSource.DataSource):
     seed = None
-    seeddir = cloudinit.seeddir + '/ovf'
+    seeddir = seeddir + '/ovf'
     environment = None
     cfg = { }
     userdata_raw = None
     metadata = None
     supported_seed_starts = ( "/" , "file://" )
 
-    def __init__(self):
-        pass
-
     def __str__(self):
         mstr="DataSourceOVF"
         mstr = mstr + " [seed=%s]" % self.seed
@@ -90,12 +87,12 @@ class DataSourceOVF(DataSource.DataSource):
                     seedfound = proto
                     break
             if not seedfound:
-                cloudinit.log.debug("seed from %s not supported by %s" %
+                self.log.debug("seed from %s not supported by %s" %
                     (seedfrom, self.__class__))
                 return False
 
             (md_seed,ud) = util.read_seeded(seedfrom)
-            cloudinit.log.debug("using seeded cache data from %s" % seedfrom)
+            self.log.debug("using seeded cache data from %s" % seedfrom)
 
             md = util.mergedict(md,md_seed)
             found.append(seedfrom)
@@ -122,7 +119,7 @@ class DataSourceOVF(DataSource.DataSource):
         return(self.cfg)
 
 class DataSourceOVFNet(DataSourceOVF):
-    seeddir = cloudinit.seeddir + '/ovf-net'
+    seeddir = seeddir + '/ovf-net'
     supported_seed_starts = ( "http://", "https://", "ftp://" )
 
 # this will return a dict with some content
@@ -283,6 +280,16 @@ def getProperties(environString):
 
     return(props)
 
+datasources = (
+  ( DataSourceOVF, ( DataSource.DEP_FILESYSTEM, ) ),
+  ( DataSourceOVFNet, 
+    ( DataSource.DEP_FILESYSTEM, DataSource.DEP_NETWORK ) ),
+)
+
+# return a list of data sources that match this set of dependencies
+def get_datasource_list(depends):
+    return(DataSource.list_from_depends(depends, datasources))
+
 if __name__ == "__main__":
     import sys
     envStr = open(sys.argv[1]).read()