Puppet users - Apr 2007 - Replacing packages

Greetings list-members!  I''m a puppet newb and I''m trying to
write a
recipe that replaces the standard Redhat sysklogd with syslog-ng.  I  
do this to separate shorewall-generated iptables log messages from / 
var/log/messages into a separate log.

I have something that works now but it spews warnings every time  
puppetd runs on the client.  The outline of what I wanted was to

   - install syslog-ng
   - configure syslog-ng
   - stop the syslog service
   - start syslog-ng
   - uninstall the sysklogd package
   - remove sysklogd configuration files


Ordering is important here since:
   - rpm dependencies require that at least one syslog be installed  
at any time
   - stopping a service requires that package to be present

My first stab at puppet code for this was like so (edited for  
brevity''s sake):

class syslog-ng {
	package { syslog-ng:
		ensure => installed,
		before => Package[sysklogd]
	}

	# ... blah blah configure syslog-ng

	package { sysklogd:
		ensure => absent,
	}
	
	file { ["/etc/syslog.conf", "/etc/sysconfig/syslog"]:
		ensure => absent,
		require => Package[sysklogd],
	}

	service { syslog:
		ensure => stopped,
		enable => false,
		before => Package[sysklogd],
	}
}

So I think this sets up all the ordering constraints that I need and  
it switches out the packages the first time through.

The problem is that the next time through, service syslog fails  
because /etc/init.d/syslog isn''t there.  That sets off a cascade of  
other warnings about failed dependencies.  Even worse, had I  
interrupted puppet after the service was stopped and package removed  
but before the other stuff was cleaned up those things never would be  
cleaned up.

So this leads me to these questions:

   - is there a way to ignore the outcome of a resource for the  
purposes of dependencies?

   - alternatively, is there a way to specify ordering without actual  
dependency on outcome?

   - barring that, can I do something like onlyif on a service to  
test for /etc/init.d/syslog myself?

   - am I missing some essential puppetism that would make this whole  
problem easier and would sidestep the above issues?

Thanks in advance!

-Marek Gilbert

On Apr 30, 2007, at 12:56 AM, Marek Gilbert wrote:
> My first stab at puppet code for this was like so (edited for
> brevity''s sake):
> [...]
Ok.
> So I think this sets up all the ordering constraints that I need and
> it switches out the packages the first time through.
>
> The problem is that the next time through, service syslog fails
> because /etc/init.d/syslog isn''t there.  That sets off a cascade
of
> other warnings about failed dependencies.  Even worse, had I
> interrupted puppet after the service was stopped and package removed
> but before the other stuff was cleaned up those things never would be
> cleaned up.
So removing the package doesn''t automatically stop the service?   
That''s what I would expect.

Otherwise... This is always going to be hard, because you can only  
talk about the service if the package is present, which will only be  
the case on the first run, and Puppet doesn''t support that at this  
point.
> So this leads me to these questions:
>
>    - is there a way to ignore the outcome of a resource for the
> purposes of dependencies?
Unfortunately, no.
>    - alternatively, is there a way to specify ordering without actual
> dependency on outcome?
Similarly, no.
>    - barring that, can I do something like onlyif on a service to
> test for /etc/init.d/syslog myself?
Three for three, no.
>    - am I missing some essential puppetism that would make this whole
> problem easier and would sidestep the above issues?
I don''t think so, but maybe you''re trying to have Puppet do
too much
and the packaging system do too little.  I''d be surprised if the  
packaging system didn''t stop the service for you, which means you  
just need to remove the package and configuration file, and not worry  
about the service.

  --
  Neonle will continue to be rude, and will nretend that you had a small
  stroke which makes you unable to say or see the letter "n".  Stunid
  nractical joke, if you ask me.  Bunch of noon-heads, huh?
                  -- Fred Barling, Humorscope
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