Silence queue enumeration "normal" errors

Fix leoarnold#251.

.github/README.md

@@ -543,7 +543,9 @@ Installs, configures, and manages the CUPS service.
 * `papersize`: Sets the system's default `/etc/papersize`. See `man papersize` for supported values.
 
 * `purge_unmanaged_queues`: Setting `true` will remove all queues from the node
-  which do not match a `cups_queue` resource in the current catalog. Defaults to `false`.
+  which do not match a `cups_queue` resource in the current catalog. Silently
+  ignored if the Cups server is not reachable when Puppet starts. Defaults to
+  `false`.
 
 * `resources`: This attribute is intended for use with Hiera or any other ENC (see the [example above](#using-hiera)).
 

README.md.erb

@@ -545,7 +545,9 @@ Installs, configures, and manages the CUPS service.
 * `papersize`: Sets the system's default `/etc/papersize`. See `man papersize` for supported values.
 
 * `purge_unmanaged_queues`: Setting `true` will remove all queues from the node
-  which do not match a `cups_queue` resource in the current catalog. Defaults to `false`.
+  which do not match a `cups_queue` resource in the current catalog. Silently
+  ignored if the Cups server is not reachable when Puppet starts. Defaults to
+  `false`.
 
 * `resources`: This attribute is intended for use with Hiera or any other ENC (see the [example above](#using-hiera)).
 

lib/puppet/provider/cups_queue/cups.rb

@@ -15,12 +15,34 @@
   ### Static provider methods
 
   def self.instances
+    discover_class_instances + discover_printer_instances
+  rescue PuppetX::Cups::Ipp::QueryError => e
+    # Connecting to Cups may fail because it is not running yet. As Puppet
+    # tries to enumerate instances before applying the catalog, no amount of
+    # resource ordering will allow to start the service before we try to
+    # connect to it.
+    #
+    # Furthermore, the desired state might be to stop the service or to not
+    # manage it at all.
+    #
+    # Therefore, purge_unmanaged_queues => true may fail for reasons we can't
+    # fix, and scare the users with a big red error message (or worse, lead to
+    # ignore-the-errors mindset). We thus prefer to silence the error here.
+    # It's still in the debug log if one cares.
+    debug("Cups queues enumeration failed (this is normal if the cups service isn't running yet):\n" + e.message)
+    []
+  end
+
+  def self.discover_class_instances
     providers = []
-    # Discover class instances
     PuppetX::Cups::Instances.class_members.each do |class_name, member_names|
       providers << new(name: class_name, ensure: :class, members: member_names)
     end
-    # Discover printer instances
+    providers
+  end
+
+  def self.discover_printer_instances
+    providers = []
     PuppetX::Cups::Instances.printers.each do |printer_name|
       providers << new(name: printer_name, ensure: :printer)
     end

manifests/init.pp

@@ -51,7 +51,8 @@
 # @param page_log_format Sets the `PageLogFormat` directive of the CUPS server.
 # @param papersize Sets the system's default `/etc/papersize`. See `man papersize` for supported values.
 # @param purge_unmanaged_queues Setting `true` will remove all queues from the node
-#   which do not match a `cups_queue` resource in the current catalog.
+#   which do not match a `cups_queue` resource in the current catalog. Silently
+#   ignored if the Cups server is not reachable when Puppet starts.
 # @param resources This attribute is intended for use with Hiera or any other ENC.
 # @param server_alias Sets the `ServerAlias` directive of the CUPS server.
 # @param server_name Sets the `ServerName` directive of the CUPS server.

spec/acceptance/classes/cups_purge_unmanaged_queues_spec.rb

@@ -14,4 +14,19 @@
       end
     end
   end
+
+  context 'when the Cups service is running' do
+    before(:all) do
+      ensure_cups_is_running
+      purge_all_queues
+      add_printers('Office')
+    end
+
+    let(:manifest) { 'class { "cups": purge_unmanaged_queues => true }' }
+
+    it 'purges unmanaged queues' do
+      apply_manifest(manifest, expect_changes: true)
+      shell('lpstat -p Office', acceptable_exit_codes: [1])
+    end
+  end
 end