set_hostname: When present in metadata, set it before network bringup.

When instance meta-data provides hostname information, run
cc_set_hostname in the init-local or init-net stage before network
comes up.

Prevent an initial DHCP request which leaks the stock cloud-image default
hostname before the meta-data provided hostname was processed.
A leaked cloud-image hostname adversely affects Dynamic DNS which
would reallocate 'ubuntu' hostname in DNS to every instance brought up by
cloud-init. These instances would only update DNS to the cloud-init
configured hostname upon DHCP lease renewal.

This branch extends the get_hostname methods in datasource, cloud and
util to limit results to metadata_only to avoid extra cost of querying
the distro for hostname information if metadata does not provide that
information.

LP: #1746455

1 files changed, 74 insertions, 0 deletions

diff --git a/cloudinit/tests/test_util.py b/cloudinit/tests/test_util.py
index c3e2e404..d30643dc 100644
--- a/cloudinit/tests/test_util.py
+++ b/cloudinit/tests/test_util.py
@@ -16,6 +16,25 @@ MOUNT_INFO = [
 ]
 
 
+class FakeCloud(object):
+
+    def __init__(self, hostname, fqdn):
+        self.hostname = hostname
+        self.fqdn = fqdn
+        self.calls = []
+
+    def get_hostname(self, fqdn=None, metadata_only=None):
+        myargs = {}
+        if fqdn is not None:
+            myargs['fqdn'] = fqdn
+        if metadata_only is not None:
+            myargs['metadata_only'] = metadata_only
+        self.calls.append(myargs)
+        if fqdn:
+            return self.fqdn
+        return self.hostname
+
+
 class TestUtil(CiTestCase):
 
     def test_parse_mount_info_no_opts_no_arg(self):
@@ -67,3 +86,58 @@ class TestShellify(CiTestCase):
                        "'echo' 'hi' 'sis'", ""]),
             util.shellify(["echo hi mom", ["echo", "hi dad"],
                            ('echo', 'hi', 'sis')]))
+
+
+class TestGetHostnameFqdn(CiTestCase):
+
+    def test_get_hostname_fqdn_from_only_cfg_fqdn(self):
+        """When cfg only has the fqdn key, derive hostname and fqdn from it."""
+        hostname, fqdn = util.get_hostname_fqdn(
+            cfg={'fqdn': 'myhost.domain.com'}, cloud=None)
+        self.assertEqual('myhost', hostname)
+        self.assertEqual('myhost.domain.com', fqdn)
+
+    def test_get_hostname_fqdn_from_cfg_fqdn_and_hostname(self):
+        """When cfg has both fqdn and hostname keys, return them."""
+        hostname, fqdn = util.get_hostname_fqdn(
+            cfg={'fqdn': 'myhost.domain.com', 'hostname': 'other'}, cloud=None)
+        self.assertEqual('other', hostname)
+        self.assertEqual('myhost.domain.com', fqdn)
+
+    def test_get_hostname_fqdn_from_cfg_hostname_with_domain(self):
+        """When cfg has only hostname key which represents a fqdn, use that."""
+        hostname, fqdn = util.get_hostname_fqdn(
+            cfg={'hostname': 'myhost.domain.com'}, cloud=None)
+        self.assertEqual('myhost', hostname)
+        self.assertEqual('myhost.domain.com', fqdn)
+
+    def test_get_hostname_fqdn_from_cfg_hostname_without_domain(self):
+        """When cfg has a hostname without a '.' query cloud.get_hostname."""
+        mycloud = FakeCloud('cloudhost', 'cloudhost.mycloud.com')
+        hostname, fqdn = util.get_hostname_fqdn(
+            cfg={'hostname': 'myhost'}, cloud=mycloud)
+        self.assertEqual('myhost', hostname)
+        self.assertEqual('cloudhost.mycloud.com', fqdn)
+        self.assertEqual(
+            [{'fqdn': True, 'metadata_only': False}], mycloud.calls)
+
+    def test_get_hostname_fqdn_from_without_fqdn_or_hostname(self):
+        """When cfg has neither hostname nor fqdn cloud.get_hostname."""
+        mycloud = FakeCloud('cloudhost', 'cloudhost.mycloud.com')
+        hostname, fqdn = util.get_hostname_fqdn(cfg={}, cloud=mycloud)
+        self.assertEqual('cloudhost', hostname)
+        self.assertEqual('cloudhost.mycloud.com', fqdn)
+        self.assertEqual(
+            [{'fqdn': True, 'metadata_only': False},
+             {'metadata_only': False}], mycloud.calls)
+
+    def test_get_hostname_fqdn_from_passes_metadata_only_to_cloud(self):
+        """Calls to cloud.get_hostname pass the metadata_only parameter."""
+        mycloud = FakeCloud('cloudhost', 'cloudhost.mycloud.com')
+        hostname, fqdn = util.get_hostname_fqdn(
+            cfg={}, cloud=mycloud, metadata_only=True)
+        self.assertEqual(
+            [{'fqdn': True, 'metadata_only': True},
+             {'metadata_only': True}], mycloud.calls)
+
+# vi: ts=4 expandtab