config_drive: ensure the search locations are ordered alphabetically

The internal Python implementation for the configured config drive
search locations is not deterministic.

Make it deterministic by using alphabetically sorted order.

In this case, the search order becomes:

  - type: iso, vfat
  - location: cdrom, hdd, partition

Change-Id: I622700c9408d3acee6d44eabfd73c662df7e7cfd
Signed-off-by: Adrian Vladu <avladu@cloudbasesolutions.com>

Author: ader1990

cloudbaseinit/constant.py

@@ -13,21 +13,21 @@
 #    under the License.
 
 # Config Drive types and possible locations.
-CD_TYPES = {
-    "vfat",    # Visible device (with partition table).
+CD_TYPES = sorted({
     "iso",     # "Raw" format containing ISO bytes.
-}
-CD_LOCATIONS = {
-    # Look into optical devices. Only an ISO format could be
-    # used here (vfat ignored).
-    "cdrom",
-    # Search through physical disks for raw ISO content or vfat filesystems
-    # containing configuration drive's content.
-    "hdd",
+    "vfat",    # Visible device (with partition table).
+})
+CD_LOCATIONS = sorted({
     # Search through partitions for raw ISO content or through volumes
     # containing configuration drive's content.
     "partition",
-}
+    # Search through physical disks for raw ISO content or vfat filesystems
+    # containing configuration drive's content.
+    "hdd",
+    # Look into optical devices. Only an ISO format could be
+    # used here (vfat ignored).
+    "cdrom",
+})
 
 POLICY_IGNORE_ALL_FAILURES = "ignoreallfailures"
 

cloudbaseinit/metadata/services/baseconfigdrive.py

@@ -39,31 +39,38 @@ def __init__(self, drive_label, metadata_file,
         self._metadata_file = metadata_file
         self._userdata_file = userdata_file
         self._metadata_path = None
-        self._searched_types = set()
-        self._searched_locations = set()
+        self._searched_types = list()
+        self._searched_locations = list()
 
     def _preprocess_options(self):
-        self._searched_types = set(CONF.config_drive.types)
-        self._searched_locations = set(CONF.config_drive.locations)
+        self._searched_types = sorted(set(CONF.config_drive.types))
+        self._searched_locations = sorted(set(CONF.config_drive.locations))
 
         # Deprecation backward compatibility.
-        if CONF.config_drive.raw_hdd:
-            self._searched_types.add("iso")
-            self._searched_locations.add("hdd")
         if CONF.config_drive.cdrom:
-            self._searched_types.add("iso")
-            self._searched_locations.add("cdrom")
+            self._searched_types.append("iso")
+            self._searched_locations.append("cdrom")
+        if CONF.config_drive.raw_hdd:
+            self._searched_types.append("iso")
+            self._searched_locations.append("hdd")
         if CONF.config_drive.vfat:
-            self._searched_types.add("vfat")
-            self._searched_locations.add("hdd")
+            self._searched_types.append("vfat")
+            self._searched_locations.append("hdd")
 
         # Check for invalid option values.
-        if self._searched_types | CD_TYPES != CD_TYPES:
+        SCD_TYPES = set(CD_TYPES)
+        if set(self._searched_types) | SCD_TYPES != SCD_TYPES:
             raise exception.CloudbaseInitException(
                 "Invalid Config Drive types %s", self._searched_types)
-        if self._searched_locations | CD_LOCATIONS != CD_LOCATIONS:
+        SCD_LOCATIONS = set(CD_LOCATIONS)
+        if set(self._searched_locations) | SCD_LOCATIONS != SCD_LOCATIONS:
             raise exception.CloudbaseInitException(
                 "Invalid Config Drive locations %s", self._searched_locations)
+        # Note(avladu): sort the order of the searched locations
+        # This is needed to be sure that the order is respected
+        # See: https://github.com/cloudbase/cloudbase-init/issues/200
+        self._searched_types = sorted(set(self._searched_types))
+        self._searched_locations = sorted(set(self._searched_locations))
 
     def load(self):
         super(BaseConfigDriveService, self).load()

cloudbaseinit/tests/metadata/services/test_baseconfigdrive.py

@@ -70,17 +70,17 @@ def _test_preprocess_options(self, fail=False):
             "cdrom": False,
             "vfat": True,
             # Deprecated options above.
-            "types": ["vfat", "iso"],
+            "types": ["iso", "vfat"],
             "locations": ["partition"]
         }
         contexts = [testutils.ConfPatcher(key, value, group="config_drive")
                     for key, value in options.items()]
         with contexts[0], contexts[1], contexts[2], \
                 contexts[3], contexts[4]:
             self._config_drive._preprocess_options()
-            self.assertEqual({"vfat", "iso"},
+            self.assertEqual(["iso", "vfat"],
                              self._config_drive._searched_types)
-            self.assertEqual({"hdd", "partition"},
+            self.assertEqual(["hdd", "partition"],
                              self._config_drive._searched_locations)
 
     def test_preprocess_options_fail(self):