Implement ntp client spec with auto support for distro selection

Add a base NTP client configuration dictionary and allow Distro
specific changes to be merged.  Add a select client function which
implements logic to preferr installed clients over clients which
need to be installed.  Also allow distributions to override the
cloud-init defaults.

LP: #1749722

1 files changed, 12 insertions, 0 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index 55260eae..6c22b07f 100755
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -49,6 +49,9 @@ LOG = logging.getLogger(__name__)
 # It could break when Amazon adds new regions and new AZs.
 _EC2_AZ_RE = re.compile('^[a-z][a-z]-(?:[a-z]+-)+[0-9][a-z]$')
 
+# Default NTP Client Configurations
+PREFERRED_NTP_CLIENTS = ['chrony', 'systemd-timesyncd', 'ntp', 'ntpdate']
+
 
 @six.add_metaclass(abc.ABCMeta)
 class Distro(object):
@@ -60,6 +63,7 @@ class Distro(object):
     tz_zone_dir = "/usr/share/zoneinfo"
     init_cmd = ['service']  # systemctl, service etc
     renderer_configs = {}
+    _preferred_ntp_clients = None
 
     def __init__(self, name, cfg, paths):
         self._paths = paths
@@ -339,6 +343,14 @@ class Distro(object):
             contents.write("%s\n" % (eh))
             util.write_file(self.hosts_fn, contents.getvalue(), mode=0o644)
 
+    @property
+    def preferred_ntp_clients(self):
+        """Allow distro to determine the preferred ntp client list"""
+        if not self._preferred_ntp_clients:
+            self._preferred_ntp_clients = list(PREFERRED_NTP_CLIENTS)
+
+        return self._preferred_ntp_clients
+
     def _bring_up_interface(self, device_name):
         cmd = ['ifup', device_name]
         LOG.debug("Attempting to run bring up interface %s using command %s",