add prefer_fqdn_over_hostname config option (#859)

the above option allows the user to control the behavior of a distro
hostname selection if both short hostname and FQDN are supplied.
If `prefer_fqdn_over_hostname` is true the FQDN will be selected as
hostname; if false the hostname will be selected

LP: #1921004

2 files changed, 72 insertions, 14 deletions

diff --git a/tests/integration_tests/modules/test_set_hostname.py b/tests/integration_tests/modules/test_set_hostname.py
index 2bfa403d..e7f7f6b6 100644
--- a/tests/integration_tests/modules/test_set_hostname.py
+++ b/tests/integration_tests/modules/test_set_hostname.py
@@ -24,6 +24,13 @@ hostname: cloudinit1
 fqdn: cloudinit2.i9n.cloud-init.io
 """
 
+USER_DATA_PREFER_FQDN = """\
+#cloud-config
+prefer_fqdn_over_hostname: {}
+hostname: cloudinit1
+fqdn: cloudinit2.test.io
+"""
+
 
 @pytest.mark.ci
 class TestHostname:
@@ -33,6 +40,16 @@ class TestHostname:
         hostname_output = client.execute("hostname")
         assert "cloudinit2" in hostname_output.strip()
 
+    @pytest.mark.user_data(USER_DATA_PREFER_FQDN.format(True))
+    def test_prefer_fqdn(self, client):
+        hostname_output = client.execute("hostname")
+        assert "cloudinit2.test.io" in hostname_output.strip()
+
+    @pytest.mark.user_data(USER_DATA_PREFER_FQDN.format(False))
+    def test_prefer_short_hostname(self, client):
+        hostname_output = client.execute("hostname")
+        assert "cloudinit1" in hostname_output.strip()
+
     @pytest.mark.user_data(USER_DATA_FQDN)
     def test_hostname_and_fqdn(self, client):
         hostname_output = client.execute("hostname")
diff --git a/tests/unittests/test_handler/test_handler_set_hostname.py b/tests/unittests/test_handler/test_handler_set_hostname.py
index 58abf51a..73641b70 100644
--- a/tests/unittests/test_handler/test_handler_set_hostname.py
+++ b/tests/unittests/test_handler/test_handler_set_hostname.py
@@ -15,6 +15,7 @@ import os
 import shutil
 import tempfile
 from io import BytesIO
+from unittest import mock
 
 LOG = logging.getLogger(__name__)
 
@@ -29,14 +30,53 @@ class TestHostname(t_help.FilesystemMockingTestCase):
         util.ensure_dir(os.path.join(self.tmp, 'data'))
         self.addCleanup(shutil.rmtree, self.tmp)
 
-    def _fetch_distro(self, kind):
+    def _fetch_distro(self, kind, conf=None):
         cls = distros.fetch(kind)
         paths = helpers.Paths({'cloud_dir': self.tmp})
-        return cls(kind, {}, paths)
+        conf = {} if conf is None else conf
+        return cls(kind, conf, paths)
 
-    def test_write_hostname_rhel(self):
+    def test_debian_write_hostname_prefer_fqdn(self):
         cfg = {
-            'hostname': 'blah.blah.blah.yahoo.com',
+            'hostname': 'blah',
+            'prefer_fqdn_over_hostname': True,
+            'fqdn': 'blah.yahoo.com',
+        }
+        distro = self._fetch_distro('debian', cfg)
+        paths = helpers.Paths({'cloud_dir': self.tmp})
+        ds = None
+        cc = cloud.Cloud(ds, paths, {}, distro, None)
+        self.patchUtils(self.tmp)
+        cc_set_hostname.handle('cc_set_hostname',
+                               cfg, cc, LOG, [])
+        contents = util.load_file("/etc/hostname")
+        self.assertEqual('blah.yahoo.com', contents.strip())
+
+    @mock.patch('cloudinit.distros.Distro.uses_systemd', return_value=False)
+    def test_rhel_write_hostname_prefer_hostname(self, m_uses_systemd):
+        cfg = {
+            'hostname': 'blah',
+            'prefer_fqdn_over_hostname': False,
+            'fqdn': 'blah.yahoo.com',
+        }
+        distro = self._fetch_distro('rhel', cfg)
+        paths = helpers.Paths({'cloud_dir': self.tmp})
+        ds = None
+        cc = cloud.Cloud(ds, paths, {}, distro, None)
+        self.patchUtils(self.tmp)
+        cc_set_hostname.handle('cc_set_hostname',
+                               cfg, cc, LOG, [])
+        contents = util.load_file("/etc/sysconfig/network", decode=False)
+        n_cfg = ConfigObj(BytesIO(contents))
+        self.assertEqual(
+            {'HOSTNAME': 'blah'},
+            dict(n_cfg))
+
+    @mock.patch('cloudinit.distros.Distro.uses_systemd', return_value=False)
+    def test_write_hostname_rhel(self, m_uses_systemd):
+        cfg = {
+            'hostname': 'blah',
+            'fqdn': 'blah.blah.blah.yahoo.com'
         }
         distro = self._fetch_distro('rhel')
         paths = helpers.Paths({'cloud_dir': self.tmp})
@@ -45,15 +85,16 @@ class TestHostname(t_help.FilesystemMockingTestCase):
         self.patchUtils(self.tmp)
         cc_set_hostname.handle('cc_set_hostname',
                                cfg, cc, LOG, [])
-        if not distro.uses_systemd():
-            contents = util.load_file("/etc/sysconfig/network", decode=False)
-            n_cfg = ConfigObj(BytesIO(contents))
-            self.assertEqual({'HOSTNAME': 'blah.blah.blah.yahoo.com'},
-                             dict(n_cfg))
+        contents = util.load_file("/etc/sysconfig/network", decode=False)
+        n_cfg = ConfigObj(BytesIO(contents))
+        self.assertEqual(
+            {'HOSTNAME': 'blah.blah.blah.yahoo.com'},
+            dict(n_cfg))
 
     def test_write_hostname_debian(self):
         cfg = {
-            'hostname': 'blah.blah.blah.yahoo.com',
+            'hostname': 'blah',
+            'fqdn': 'blah.blah.blah.yahoo.com',
         }
         distro = self._fetch_distro('debian')
         paths = helpers.Paths({'cloud_dir': self.tmp})
@@ -65,7 +106,8 @@ class TestHostname(t_help.FilesystemMockingTestCase):
         contents = util.load_file("/etc/hostname")
         self.assertEqual('blah', contents.strip())
 
-    def test_write_hostname_sles(self):
+    @mock.patch('cloudinit.distros.Distro.uses_systemd', return_value=False)
+    def test_write_hostname_sles(self, m_uses_systemd):
         cfg = {
             'hostname': 'blah.blah.blah.suse.com',
         }
@@ -75,9 +117,8 @@ class TestHostname(t_help.FilesystemMockingTestCase):
         cc = cloud.Cloud(ds, paths, {}, distro, None)
         self.patchUtils(self.tmp)
         cc_set_hostname.handle('cc_set_hostname', cfg, cc, LOG, [])
-        if not distro.uses_systemd():
-            contents = util.load_file(distro.hostname_conf_fn)
-            self.assertEqual('blah', contents.strip())
+        contents = util.load_file(distro.hostname_conf_fn)
+        self.assertEqual('blah', contents.strip())
 
     def test_multiple_calls_skips_unchanged_hostname(self):
         """Only new hostname or fqdn values will generate a hostname call."""