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, 8 insertions, 2 deletions

diff --git a/cloudinit/sources/DataSourceEc2.py b/cloudinit/sources/DataSourceEc2.py
index a2105dc7..8a7f7c60 100644
--- a/cloudinit/sources/DataSourceEc2.py
+++ b/cloudinit/sources/DataSourceEc2.py
@@ -8,6 +8,7 @@
 #
 # This file is part of cloud-init. See LICENSE file for license information.
 
+import copy
 import os
 import time
 
@@ -20,7 +21,7 @@ from cloudinit import sources
 from cloudinit import url_helper as uhelp
 from cloudinit import util
 from cloudinit import warnings
-from cloudinit.event import EventType
+from cloudinit.event import EventScope, EventType
 
 LOG = logging.getLogger(__name__)
 
@@ -426,7 +427,12 @@ class DataSourceEc2(sources.DataSource):
             # Non-VPC (aka Classic) Ec2 instances need to rewrite the
             # network config file every boot due to MAC address change.
             if self.is_classic_instance():
-                self.update_events['network'].add(EventType.BOOT)
+                self.default_update_events = copy.deepcopy(
+                    self.default_update_events)
+                self.default_update_events[EventScope.NETWORK].add(
+                    EventType.BOOT)
+                self.default_update_events[EventScope.NETWORK].add(
+                    EventType.BOOT_LEGACY)
         else:
             LOG.warning("Metadata 'network' key not valid: %s.", net_md)
         self._network_config = result