puppet: Pull hosts from zulip.conf, not hardcoded list.

The one complexity is that hosts_fullstack are treated differently, as
they are not currently found in the manual `hosts` list, and as such
do not get munin monitoring.

puppet/zulip/lib/puppet/parser/functions/zulipconf.rb

@@ -10,4 +10,26 @@ module Puppet::Parser::Functions
       default
     end
   end
+
+  newfunction(:zulipconf_nagios_hosts, :type => :rvalue, :arity => 0) do |args|
+    section = "nagios"
+    prefix = "hosts_"
+    ignore_key = "hosts_fullstack"
+    zulip_conf_path = lookupvar('zulip_conf_path')
+    keys = `/usr/bin/crudini --get #{zulip_conf_path} #{section} 2>&1`; result=$?.success?
+    if result
+      keys = keys.lines.map { |l| l.strip }
+      filtered_keys = keys.select { |l| l.start_with?(prefix) }.reject { |k| k == ignore_key }
+      all_values = []
+      filtered_keys.each do |key|
+        values = `/usr/bin/crudini --get #{zulip_conf_path} #{section} #{key} 2>&1`; result=$?.success?
+        if result
+          all_values += values.strip.split(/,\s*/)
+        end
+      end
+      return all_values
+    else
+      return []
+    end
+  end
 end

puppet/zulip_ops/manifests/base.pp

@@ -36,9 +36,6 @@ class zulip_ops::base {
   # Add system users here
   $users = []
 
-  # Add hosts to monitor here
-  $hosts = []
-
   file { '/etc/apt/apt.conf.d/02periodic':
     ensure => file,
     mode   => '0644',

puppet/zulip_ops/manifests/munin.pp

@@ -10,7 +10,7 @@ class zulip_ops::munin {
   package { $munin_packages: ensure => 'installed' }
 
   $default_host_domain = zulipconf('nagios', 'default_host_domain', undef)
-  $hosts = $zulip_ops::base::hosts
+  $hosts = zulipconf_nagios_hosts()
 
   file { '/etc/munin':
     require => Package['munin'],

puppet/zulip_ops/manifests/nagios.pp

@@ -105,7 +105,7 @@ class zulip_ops::nagios {
     notify => Service['nagios3'],
   }
 
-  $hosts = $zulip_ops::base::hosts
+  $hosts = zulipconf_nagios_hosts()
   file { '/etc/nagios3/conf.d/zulip_autossh.cfg':
     ensure  => file,
     mode    => '0644',