sources/azure: minor refactor for metadata source detection logic (#1936)

- Initialize md and cfg to the fallback used when no OVF is found
  and IMDS is required.

- Rename metadata_source -> ovf_source and drop usage of "IMDS" as
  a valid value.

- Set `self.seed` to "IMDS" when ovf_source is unset.

- Remove late check for metadata source.  This is already done
  by the earlier check where we'll fail with "No OVF or IMDS
  available".

- Move "Found provisioning metadata" diagnostic up to where we
  read OVF.  Suggesting it was "IMDS" prior to querying IMDS
  is misleading.

- Add warning when falling back to IMDS-only provisioning.

Signed-off-by: Chris Patterson <cpatterson@microsoft.com>

1 files changed, 21 insertions, 29 deletions

diff --git a/cloudinit/sources/DataSourceAzure.py b/cloudinit/sources/DataSourceAzure.py
index 55b8db85..8ee1bea7 100644
--- a/cloudinit/sources/DataSourceAzure.py
+++ b/cloudinit/sources/DataSourceAzure.py
@@ -527,11 +527,10 @@ class DataSourceAzure(sources.DataSource):
         # it determines the value of ret. More specifically, the first one in
         # the candidate list determines the path to take in order to get the
         # metadata we need.
-        ovf_is_accessible = False
-        metadata_source = None
-        md = {}
+        ovf_source = None
+        md = {"local-hostname": ""}
+        cfg = {"system_info": {"default_user": {"name": ""}}}
         userdata_raw = ""
-        cfg = {}
         files = {}
 
         for src in list_possible_azure_ds(self.seed_dir, ddir):
@@ -549,8 +548,12 @@ class DataSourceAzure(sources.DataSource):
                     self._iso_dev = src
                 else:
                     md, userdata_raw, cfg, files = load_azure_ds_dir(src)
-                ovf_is_accessible = True
-                metadata_source = src
+
+                ovf_source = src
+                report_diagnostic_event(
+                    "Found provisioning metadata in %s" % ovf_source,
+                    logger_func=LOG.debug,
+                )
                 break
             except NonAzureDataSource:
                 report_diagnostic_event(
@@ -562,26 +565,25 @@ class DataSourceAzure(sources.DataSource):
                 report_diagnostic_event(
                     "%s was not mountable" % src, logger_func=LOG.debug
                 )
-                md = {"local-hostname": ""}
-                cfg = {"system_info": {"default_user": {"name": ""}}}
-                metadata_source = "IMDS"
                 continue
             except BrokenAzureDataSource as exc:
                 msg = "BrokenAzureDataSource: %s" % exc
                 report_diagnostic_event(msg, logger_func=LOG.error)
                 raise sources.InvalidMetaDataException(msg)
-
-        report_diagnostic_event(
-            "Found provisioning metadata in %s" % metadata_source,
-            logger_func=LOG.debug,
-        )
+        else:
+            msg = (
+                "Unable to find provisioning media, falling back to IMDS "
+                "metadata. Be aware that IMDS metadata does not support "
+                "admin passwords or custom-data (user-data only)."
+            )
+            report_diagnostic_event(msg, logger_func=LOG.warning)
 
         # If we read OVF from attached media, we are provisioning.  If OVF
         # is not found, we are probably provisioning on a system which does
         # not have UDF support.  In either case, require IMDS metadata.
         # If we require IMDS metadata, try harder to obtain networking, waiting
         # for at least 20 minutes.  Otherwise only wait 5 minutes.
-        requires_imds_metadata = bool(self._iso_dev) or not ovf_is_accessible
+        requires_imds_metadata = bool(self._iso_dev) or ovf_source is None
         timeout_minutes = 20 if requires_imds_metadata else 5
         try:
             self._setup_ephemeral_networking(timeout_minutes=timeout_minutes)
@@ -593,7 +595,7 @@ class DataSourceAzure(sources.DataSource):
         else:
             imds_md = {}
 
-        if not imds_md and not ovf_is_accessible:
+        if not imds_md and ovf_source is None:
             msg = "No OVF or IMDS available"
             report_diagnostic_event(msg)
             raise sources.InvalidMetaDataException(msg)
@@ -619,7 +621,7 @@ class DataSourceAzure(sources.DataSource):
         # Report errors if IMDS network configuration is missing data.
         self.validate_imds_network_metadata(imds_md=imds_md)
 
-        self.seed = metadata_source
+        self.seed = ovf_source or "IMDS"
         crawled_data.update(
             {
                 "cfg": cfg,
@@ -646,7 +648,7 @@ class DataSourceAzure(sources.DataSource):
                 "disable_password"
             ] = imds_disable_password
 
-        if metadata_source == "IMDS" and not crawled_data["files"]:
+        if self.seed == "IMDS" and not crawled_data["files"]:
             try:
                 contents = build_minimal_ovf(
                     username=imds_username,  # pyright: ignore
@@ -675,17 +677,7 @@ class DataSourceAzure(sources.DataSource):
                         "Bad userdata in IMDS", logger_func=LOG.warning
                     )
 
-        if not metadata_source:
-            msg = "No Azure metadata found"
-            report_diagnostic_event(msg, logger_func=LOG.error)
-            raise sources.InvalidMetaDataException(msg)
-        else:
-            report_diagnostic_event(
-                "found datasource in %s" % metadata_source,
-                logger_func=LOG.debug,
-            )
-
-        if metadata_source == ddir:
+        if ovf_source == ddir:
             report_diagnostic_event(
                 "using files cached in %s" % ddir, logger_func=LOG.debug
             )