Support metalink in yum repository config (canonical#5444)

'metalink' config can be specified instead or along with 'baseurl' in the yum
repository config. Add support for specifying metalink instead of 'baseurl'.

Fixes canonicalGH-5359

Signed-off-by: Ani Sinha <anisinha@redhat.com>
Co-authored-by: Ben Gray <ben.gray@clearcapital.com>

cloudinit/config/cc_yum_add_repo.py

@@ -211,24 +211,22 @@ def handle(name: str, cfg: Config, cloud: Cloud, args: list) -> None:
                 n_repo_config[k] = v
         repo_config = n_repo_config
         missing_required = 0
-        for req_field in ["baseurl"]:
+        req_fields = ["baseurl", "metalink"]
+        for req_field in req_fields:
             if req_field not in repo_config:
-                LOG.warning(
-                    "Repository %s does not contain a %s"
-                    " configuration 'required' entry",
-                    repo_id,
-                    req_field,
-                )
                 missing_required += 1
-        if not missing_required:
-            repo_configs[canon_repo_id] = repo_config
-            repo_locations[canon_repo_id] = repo_fn_pth
-        else:
+
+        if missing_required == len(req_fields):
             LOG.warning(
-                "Repository %s is missing %s required fields, skipping!",
+                "Repository %s should contain atleast one of the"
+                " following configuration entries: %s, skipping!",
                 repo_id,
-                missing_required,
+                ", ".join(req_fields),
             )
+        else:
+            repo_configs[canon_repo_id] = repo_config
+            repo_locations[canon_repo_id] = repo_fn_pth
+
     for (c_repo_id, path) in repo_locations.items():
         repo_blob = _format_repository_config(
             c_repo_id, repo_configs.get(c_repo_id)

doc/examples/cloud-config-yum-repo.txt

@@ -11,8 +11,9 @@ yum_repos:
     # Any repository configuration options
     # See: man yum.conf
     #
-    # This one is required!
+    # At least one of 'baseurl' or 'metalink' is required!
     baseurl: http://download.fedoraproject.org/pub/epel/testing/5/$basearch
+    metalink: https://mirrors.fedoraproject.org/metalink?repo=epel-$releasever&arch=$basearch&infra=$infra&content=$contentdir
     enabled: false
     failovermethod: priority
     gpgcheck: true

tests/unittests/config/test_cc_yum_add_repo.py

@@ -31,6 +31,7 @@ def test_bad_config(self):
             "yum_repos": {
                 "epel-testing": {
                     "name": "Extra Packages for Enterprise Linux 5 - Testing",
+                    # At least one of baseurl or metalink must be present.
                     # Missing this should cause the repo not to be written
                     # 'baseurl': 'http://blah.org/pub/epel/testing/5/$barch',
                     "enabled": False,
@@ -46,6 +47,43 @@ def test_bad_config(self):
             IOError, util.load_text_file, "/etc/yum.repos.d/epel_testing.repo"
         )
 
+    def test_metalink_config(self):
+        cfg = {
+            "yum_repos": {
+                "epel-testing": {
+                    "name": "Extra Packages for Enterprise Linux 5 - Testing",
+                    "metalink": "http://blah.org/pub/epel/testing/5/$basearch",
+                    "enabled": False,
+                    "gpgcheck": True,
+                    "gpgkey": "file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL",
+                    "failovermethod": "priority",
+                },
+            },
+        }
+        self.patchUtils(self.tmp)
+        self.patchOS(self.tmp)
+        cc_yum_add_repo.handle("yum_add_repo", cfg, None, [])
+        contents = util.load_text_file("/etc/yum.repos.d/epel-testing.repo")
+        parser = configparser.ConfigParser()
+        parser.read_string(contents)
+        expected = {
+            "epel-testing": {
+                "name": "Extra Packages for Enterprise Linux 5 - Testing",
+                "failovermethod": "priority",
+                "gpgkey": "file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL",
+                "enabled": "0",
+                "metalink": "http://blah.org/pub/epel/testing/5/$basearch",
+                "gpgcheck": "1",
+            }
+        }
+        for section in expected:
+            self.assertTrue(
+                parser.has_section(section),
+                "Contains section {0}".format(section),
+            )
+            for k, v in expected[section].items():
+                self.assertEqual(parser.get(section, k), v)
+
     def test_write_config(self):
         cfg = {
             "yum_repos": {