Allow user control over update events (#834)

Control is currently limited to boot events, though this should
allow us to more easily incorporate HOTPLUG support. Disabling
'instance-first-boot' is not supported as we apply networking config
too early in boot to have processed userdata (along with the fact
that this would be a pretty big foot-gun).

The concept of update events on datasource has been split into
supported update events and default update events. Defaults will be
used if there is no user-defined update events, but user-defined
events won't be supplied if they aren't supported.
When applying the networking config, we now check to see if the event
is supported by the datasource as well as if it is enabled.

Configuration looks like:
updates:
  network:
    when: ['boot']

1 files changed, 10 insertions, 5 deletions

diff --git a/cloudinit/sources/DataSourceAzure.py b/cloudinit/sources/DataSourceAzure.py
index 2f3390c3..dcdf9f8f 100755
--- a/cloudinit/sources/DataSourceAzure.py
+++ b/cloudinit/sources/DataSourceAzure.py
@@ -22,7 +22,7 @@ import requests
 from cloudinit import dmi
 from cloudinit import log as logging
 from cloudinit import net
-from cloudinit.event import EventType
+from cloudinit.event import EventScope, EventType
 from cloudinit.net import device_driver
 from cloudinit.net.dhcp import EphemeralDHCPv4
 from cloudinit import sources
@@ -338,6 +338,13 @@ def temporary_hostname(temp_hostname, cfg, hostname_command='hostname'):
 class DataSourceAzure(sources.DataSource):
 
     dsname = 'Azure'
+    # Regenerate network config new_instance boot and every boot
+    default_update_events = {EventScope.NETWORK: {
+        EventType.BOOT_NEW_INSTANCE,
+        EventType.BOOT,
+        EventType.BOOT_LEGACY
+    }}
+
     _negotiated = False
     _metadata_imds = sources.UNSET
     _ci_pkl_version = 1
@@ -352,8 +359,6 @@ class DataSourceAzure(sources.DataSource):
             BUILTIN_DS_CONFIG])
         self.dhclient_lease_file = self.ds_cfg.get('dhclient_lease_file')
         self._network_config = None
-        # Regenerate network config new_instance boot and every boot
-        self.update_events['network'].add(EventType.BOOT)
         self._ephemeral_dhcp_ctx = None
         self.failed_desired_api_version = False
         self.iso_dev = None
@@ -2309,8 +2314,8 @@ def maybe_remove_ubuntu_network_config_scripts(paths=None):
                 LOG.info(
                     'Removing Ubuntu extended network scripts because'
                     ' cloud-init updates Azure network configuration on the'
-                    ' following event: %s.',
-                    EventType.BOOT)
+                    ' following events: %s.',
+                    [EventType.BOOT.value, EventType.BOOT_LEGACY.value])
                 logged = True
             if os.path.isdir(path):
                 util.del_dir(path)