Puppet users - Nov 2013 - can I pass a class or type to be executed into another class?

Hello, I have a module "mywebapp" which calls the tomcat::war module
with
specific parameters, to upgrade the war file and restart tomcat. This works 
great. What I would like to do is modify the code so that if, and only if 
tomcat needs to be restarted, BEFORE it is restarted, I want to perform a 
file operation. I want to do this because the operation will tell our load 
balancer the server is about to go offline, and not to direct any traffic 
to the server. I don''t want to do this unless the war file is actually 
going to be upgraded, which only the tomcat::war type knows.

The tomcat::war module which looks roughly like this (I''m simplifying
for
brevity):

define tomcat7::war (
    ... params
) {

  ... variable definitions ...

  file { "${tomcat7::sites_dir}/${destFile}":
    notify      =>
Exec["clean_${tomcat7::sites_dir}/${contextPath}"],
  }

  exec { "clean_${tomcat7::sites_dir}/${contextPath}":
    command     => "rm -rf ${contextPath} ; mkdir ${contextPath} ; unzip
${contextPath}.war -d ${contextPath}/",
    cwd         => "${tomcat7::sites_dir}",
    notify      => Class[''tomcat7::service''],
  }
}

what I would like to do is pass a parameter into tomcat::war so that if 
that the parameter is set, the class (or type) referenced in the parameter 
is Notified instead of
Exec["clean_${tomcat7::sites_dir}/${contextPath}"],
and then Exec["clean_${tomcat7::sites_dir}/${contextPath}"] would be 
notified AFTER my code.

This would allow my code a chance to notify the load balancer and pause 
before cleaning and restarting tomcat. I don''t want the special 
load-balancer code in tomcat::war, because it is unique to
''mywebapp''.

Is there a way to do this at all?

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Hi,

I think you''re overcomplicating.

I suppose you have something like

class mywebapp {
  tomcat7::war { "mywebapp": ... }
}

You can wrench your code inbetween if you slightly modify your defined
type like so:

define tomcat7::war(...) {
  file { "tomcat7-war-file-$name":
    path => "${tomcat7::sites_dir}/${destFile}",
    notify => Exec["clean-tomcat7-war-$name"],
  }
  exec { "clean-tomcat7-war-$name":
    ...
  }
}

to make the interface more transparent. Then add to class mywebapp:

exec { "notify-loadbalancer":
  command => ...
  suscribe => File["tomcat7-war-file-mywebapp"],
  before => Exec["clean-tomcat7-war-mywebapp"],
}

This is not exactly clean design, of course (use this pattern in enough
places and you''ve got a maintenance nightmare right on hand).

If you *want* to make it clean, you will have little choice but to
include the code in tomcat7::war after all, along with a new parameter
to explicitly enable it (e.g. $do_notify_loadbalancer = false).

If a compromise is acceptable, you may get away with making it somewhat
generic like

define tomcat7::war(
  ...
  $pre_cleanup_hook = "") {

...

  if $pre_cleanup_hook {
    exec { "tomcat7-war-pch-$name":
      command => "$pre_cleanup_hook",
      subscribe => File[...],
      before => Exec[...],
    }
  }
...
}

HTH,
Felix

On 11/26/2013 07:31 AM, Joshua Chaitin-Pollak wrote:
> what I would like to do is pass a parameter into tomcat::war so that if
> that the parameter is set, the class (or type) referenced in the
> parameter is Notified instead
> of Exec["clean_${tomcat7::sites_dir}/${contextPath}"], and
> then Exec["clean_${tomcat7::sites_dir}/${contextPath}"] would be
> notified AFTER my code.
> 
> This would allow my code a chance to notify the load balancer and pause
> before cleaning and restarting tomcat. I don''t want the special
> load-balancer code in tomcat::war, because it is unique to
''mywebapp''.
> 
> Is there a way to do this at all?
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