(FACT-2245) Add xen resolver (#532)

lib/facts/linux/virtual.rb

@@ -7,7 +7,7 @@ class Virtual
 
       def call_the_resolver
         fact_value = check_docker_lxc || check_gce || retrieve_from_virt_what || check_vmware
-        fact_value ||= check_open_vz || check_vserver
+        fact_value ||= check_open_vz || check_vserver || check_xen
 
         Facter::ResolvedFact.new(FACT_NAME, fact_value)
       end
@@ -36,6 +36,10 @@ def check_open_vz
       def check_vserver
         Facter::Resolvers::VirtWhat.resolve(:vserver)
       end
+
+      def check_xen
+        Facter::Resolvers::Xen.resolve(:vm)
+      end
     end
   end
 end

lib/resolvers/xen.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module Facter
+  module Resolvers
+    class Xen < BaseResolver
+      @semaphore = Mutex.new
+      @fact_list ||= {}
+
+      class << self
+        private
+
+        def post_resolve(fact_name)
+          @fact_list.fetch(fact_name) { chech_xen_dirs(fact_name) }
+        end
+
+        def chech_xen_dirs(fact_name)
+          xen_type = 'xen0' if File.exist?('/dev/xen/evtchn')
+          xen_type = 'xenu' if !xen_type && (File.exist?('/proc/xen') || File.exist?('/dev/xvda1'))
+
+          @fact_list[:vm] = xen_type
+          @fact_list[fact_name]
+        end
+      end
+    end
+  end
+end

spec/facter/facts/linux/virtual_spec.rb

@@ -93,6 +93,20 @@
       end
     end
 
+    context 'when is xen priviledged' do
+      let(:vm) { nil }
+      let(:value) { 'xen0' }
+
+      before do
+        allow(Facter::Resolvers::Xen).to receive(:resolve).with(:vm).and_return(value)
+      end
+
+      it 'returns virtual fact' do
+        expect(fact.call_the_resolver).to be_an_instance_of(Facter::ResolvedFact).and \
+          have_attributes(name: 'virtual', value: value)
+      end
+    end
+
     context 'when resolver returns nil' do
       let(:vm) { nil }
 

spec/facter/resolvers/xen_spec.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+describe Facter::Resolvers::Xen do
+  subject(:xen_resolver) { Facter::Resolvers::Xen }
+
+  let(:proc_xen_file) { false }
+  let(:xvda1_file) { false }
+
+  before do
+    allow(File).to receive(:exist?).with('/dev/xen/evtchn').and_return(evtchn_file)
+    allow(File).to receive(:exist?).with('/proc/xen').and_return(proc_xen_file)
+    allow(File).to receive(:exist?).with('/dev/xvda1').and_return(xvda1_file)
+    xen_resolver.invalidate_cache
+  end
+
+  context 'when is priviledged xen' do
+    let(:evtchn_file) { true }
+
+    it 'returns xen0' do
+      expect(xen_resolver.resolve(:vm)).to eq('xen0')
+    end
+
+    it 'does not check other files' do
+      expect(File).not_to have_received(:exist?).with('/proc/xen')
+    end
+  end
+
+  context 'when is unpriviledged xen' do
+    let(:evtchn_file) { false }
+    let(:xvda1_file) { true }
+
+    it 'returns xenu' do
+      expect(xen_resolver.resolve(:vm)).to eq('xenu')
+    end
+  end
+end