Re: [et-mgmt-tools] [PATCH] Cobbler: recommendation for pre/post synchronization trigger implementation

Michael DeHaan <mdehaan@xxxxxxxxxx> · Tue, 05 Jun 2007 11:23:34 -0400

Adam Rosenwald wrote:

I'll check this patch out shortly... It looks pretty good to me. Thanks!

I spoke with Michael somewhat on IRC regarding my desire to implement 
a DNS zone-related trigger mechanism. My main problem was that cobbler 
"core" (as opposed to "triggers") enforced a policy on trigger 
writers. When adding a new system (generically speaking, "cobbler 
system add --name=<ip│mac│hostname | default> --profile=<string>", 
where --name=hostname, and hostname != <resolveable hostname>, cobbler 
prevents the system addition.
FYI -- This is already removed in upstream. (Cobbler system add 
--name=foo --mac=AA:BB:CC:DD:EE:FF) is now legal, and things work 
appropriately. If you leave off the --mac and the --ip, the system can't 
PXE, but it can still live in the config. Implict adds such as "cobbler 
system add --name=AA:BB:CC:DD:EE:FF" will automatically set the mac 
address, as before.


This presented much difficulty in adding zone entries to systems that 
didn't yet exist in DNS (chicken and egg). If that were not enough 
trouble, if I would then remove the checking mechanism (as seen in 
action_sync.py:get_pxe_filename() method), the sync occurs regardless 
whether my own 'valid hostname' checks could be utilized.

I asked Michael if there were a way to push such policy mechanisms 
(there really is only one -- the system.name <http://system.name> 
check) to the trigger writers, so I might have a way to enforce my 
checks. Rather than to rewrite the control of the add method (whose 
utility outweighs its rarely-seen limitations), Michael recommended 
some options including the solution I'm offering.

With the following minor patch and the addition of 
../trigger/system/{add,remove}/{pre,post} directories, triggers that 
either make use of custom checks (which conflict with those in 
get_pxe_filename()) and/or need to be executed prior to syncs, can 
then be placed in the .../pre/... directories. Those triggers which 
may be executed without these requirements can be placed in the 
.../post/... directories.

I am able to refer to "sys.argv[1]" within my trigger, and this will 
refer to the --name. Then, I can make use of --name within my 
pre_trigger and perform custom checks, dns zone instantiation, etc. 
before returning control to cobbler core, where the core name checks 
are then performed. Normal triggers would be called after sync as they 
currently are, but they are to be found in the .../post/... directory.
Yup...

There are other ways of implementing the mechanism. Perhaps only one 
trigger directory is needed with checked filename prefixes or suffixes 
for pre/post. I am only following the existing mechanism in adding the 
directories. If there are more elegant or efficient mechanisms, it 
will likely be part of a complete trigger system rehaul, as Michael 
has alluded to...
The main thing I want to see is pre-triggers filtering checking return 
codes, so as to reject additions to the config if any of the 
pre-triggers fail. This is pretty simple.

Post-return codes also need to be paid attention to, which is something 
the current cobbler system doesn't do either :) ...



If you would like to use this patch, you will have to rebuild with the 
following changes to the specfile and setup.py:

--- cobbler.spec.orig 2007-04-26 22:03:04.000000000 +0000
+++ cobbler.spec 2007-06-04 23:35:23.000000000 +0000
@@ -105,14 +105,22 @@
%dir /var/log/cobbler/syslog
%defattr(2550,root,root)
%dir /var/lib/cobbler
-%dir /var/lib/cobbler/triggers/add/distro
-%dir /var/lib/cobbler/triggers/add/profile
-%dir /var/lib/cobbler/triggers/add/system
-%dir /var/lib/cobbler/triggers/add/repo
-%dir /var/lib/cobbler/triggers/delete/distro
-%dir /var/lib/cobbler/triggers/delete/profile
-%dir /var/lib/cobbler/triggers/delete/system
-%dir /var/lib/cobbler/triggers/delete/repo
+%dir /var/lib/cobbler/triggers/add/distro/pre
+%dir /var/lib/cobbler/triggers/add/distro/post
+%dir /var/lib/cobbler/triggers/add/profile/pre
+%dir /var/lib/cobbler/triggers/add/profile/post
+%dir /var/lib/cobbler/triggers/add/system/pre
+%dir /var/lib/cobbler/triggers/add/system/post
+%dir /var/lib/cobbler/triggers/add/repo/pre
+%dir /var/lib/cobbler/triggers/add/repo/post
+%dir /var/lib/cobbler/triggers/delete/distro/pre
+%dir /var/lib/cobbler/triggers/delete/distro/post
+%dir /var/lib/cobbler/triggers/delete/profile/pre
+%dir /var/lib/cobbler/triggers/delete/profile/post
+%dir /var/lib/cobbler/triggers/delete/system/pre
+%dir /var/lib/cobbler/triggers/delete/system/post
+%dir /var/lib/cobbler/triggers/delete/repo/pre
+%dir /var/lib/cobbler/triggers/delete/repo/post
/var/lib/cobbler/elilo-3.6-ia64.efi
/var/lib/cobbler/menu.c32
%defattr(-,root,root)

--- setup.py.orig 2007-04-26 18:03:12.000000000 -0400
+++ setup.py 2007-06-04 22:05:22.000000000 -0400
@@ -78,14 +78,22 @@
(vw_links, []),
(tftp_cfg, []),
(tftp_images, []),
- ("/var/lib/cobbler/triggers/add/distro", []),
- ("/var/lib/cobbler/triggers/add/profile", []),
- ("/var/lib/cobbler/triggers/add/system", []),
- ("/var/lib/cobbler/triggers/add/repo", []),
- ("/var/lib/cobbler/triggers/delete/distro", []),
- ("/var/lib/cobbler/triggers/delete/profile", []),
- ("/var/lib/cobbler/triggers/delete/system", []),
- ("/var/lib/cobbler/triggers/delete/repo", [])
+ ("/var/lib/cobbler/triggers/add/distro/pre", []),
+ ("/var/lib/cobbler/triggers/add/distro/post", []),
+ ("/var/lib/cobbler/triggers/add/profile/pre", []),
+ ("/var/lib/cobbler/triggers/add/profile/post", []),
+ ("/var/lib/cobbler/triggers/add/system/pre", []),
+ ("/var/lib/cobbler/triggers/add/system/post", []),
+ ("/var/lib/cobbler/triggers/add/repo/pre", []),
+ ("/var/lib/cobbler/triggers/add/repo/post", []),
+ ("/var/lib/cobbler/triggers/delete/distro/pre", []),
+ ("/var/lib/cobbler/triggers/delete/distro/post", []),
+ ("/var/lib/cobbler/triggers/delete/profile/pre", []),
+ ("/var/lib/cobbler/triggers/delete/profile/post", []),
+ ("/var/lib/cobbler/triggers/delete/system/pre", []),
+ ("/var/lib/cobbler/triggers/delete/system/post", []),
+ ("/var/lib/cobbler/triggers/delete/repo/pre", [])
+ ("/var/lib/cobbler/triggers/delete/repo/post", [])
],
description = SHORT_DESC,
long_description = LONG_DESC


The actual core patches are listed below

--- cobbler/collection_distros.py.orig 2007-04-16 15:57:29.000000000 -0400
+++ cobbler/collection_distros.py 2007-06-04 21:38:33.000000000 -0400
@@ -51,9 +51,10 @@
raise cexceptions.CobblerException("orphan_profile",v.name 
<http://v.name>)
if self.find(name):
if with_delete:
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/distro/pre/*")
lite_sync = action_litesync.BootLiteSync(self.config)
lite_sync.remove_single_profile(name)
- self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/distro/*")
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/distro/post/*")
del self.listing[name]
return True
raise cexceptions.CobblerException("delete_nothing")
--- cobbler/collection_profiles.py.orig 2007-04-16 15:07:37.000000000 
-0400
+++ cobbler/collection_profiles.py 2007-06-04 21:39:01.000000000 -0400
@@ -48,9 +48,10 @@
raise cexceptions.CobblerException("orphan_system",v.name <http://v.name>)
if self.find(name):
if with_delete:
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/profile/pre/*")
lite_sync = action_litesync.BootLiteSync(self.config)
lite_sync.remove_single_profile(name)
- self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/profile/*")
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/profile/post/*")
del self.listing[name]
return True
raise cexceptions.CobblerException("delete_nothing")
--- cobbler/collection_systems.py.orig 2007-04-16 15:07:47.000000000 -0400
+++ cobbler/collection_systems.py 2007-06-04 21:41:11.000000000 -0400
@@ -49,9 +49,10 @@
"""
if self.find(name):
if with_delete:
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/system/pre/*")
lite_sync = action_litesync.BootLiteSync(self.config)
lite_sync.remove_single_system(name)
- self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/system/*")
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/system/post/*")
del self.listing[name]
return True
raise cexceptions.CobblerException("delete_nothing")
--- cobbler/collection_repos.py.orig 2007-04-20 18:54:24.000000000 -0400
+++ cobbler/collection_repos.py 2007-06-04 21:40:25.000000000 -0400
@@ -52,8 +52,9 @@
# but is left in for consistancy in the API.

if self.find(name):
- self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/repo/*")
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/repo/pre/*")
del self.listing[name]
+ self._run_triggers(self.listing[name], 
"/var/lib/cobbler/triggers/delete/repo/post/*")
return True
raise cexceptions.CobblerException("delete_nothing")

--- cobbler/collection.py.orig 2007-04-20 16:14:52.000000000 -0400
+++ cobbler/collection.py 2007-06-04 21:35:46.000000000 -0400
@@ -91,6 +91,7 @@

# perform filesystem operations
if with_copy:
+ self._run_triggers(ref,"/var/lib/cobbler/triggers/add/%s/pre/*" % 
self.collection_type())
lite_sync = action_litesync.BootLiteSync(self.config)
if isinstance(ref, item_system.System):
lite_sync.add_single_system(ref.name <http://ref.name>)
@@ -103,8 +104,8 @@

# save the tree, so if neccessary, scripts can examine it.
self.config.api.serialize()
-
- self._run_triggers(ref,"/var/lib/cobbler/triggers/add/%s/*" % 
self.collection_type())
+
+ self._run_triggers(ref,"/var/lib/cobbler/triggers/add/%s/post/*" % 
self.collection_type())

return True


--Adam.
------------------------------------------------------------------------

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