Implement os_workers_heat_engine

Re-using the classic os_workers fact but changing the minimum from 2 to
4, specific to the fact Heat Engine can be stressed out.
Also cap to 24 workers at maximum.

Change-Id: I31d02bea6dd55d65a7014503398adc4422ce7303

lib/facter/os_workers.rb

@@ -48,3 +48,16 @@ Facter.add(:os_workers_large) do
     [ (processors.to_i / 2), 1 ].max
   end
 end
+
+#
+# Heat Engine service can be more stressed than other services, so
+# a minimum of 4 and maximum of 24 workers should be fine, still
+# calculating with the number of processors.
+#
+Facter.add(:os_workers_heat_engine) do
+  has_weight 100
+  setcode do
+    processors = Facter.value('processorcount')
+    [ [ (processors.to_i / 2), 4 ].max, 24 ].min
+  end
+end

releasenotes/notes/os_workers_heat_engine-af8ce1fdf3ce1ae1.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    Implement a new fact, $::os_workers_heat_engine that is responding to
+    a specific need with Heat Engine service, where minimum of workers will
+    be 4 and maximum of 24.

spec/unit/facter/os_workers_heat_engine_spec.rb

@@ -0,0 +1,36 @@
+require 'spec_helper'
+
+describe 'os_workers_heat_engine' do
+
+  before { Facter.flush }
+
+  context 'with processorcount=1' do
+    before do
+      Facter.fact(:processorcount).stubs(:value).returns(1)
+    end
+
+    it 'returns a minimum of 2' do
+      expect(Facter.fact(:os_workers_heat_engine).value).to eq(4)
+    end
+  end
+
+  context 'with processorcount=8' do
+    before do
+      Facter.fact(:processorcount).stubs(:value).returns(8)
+    end
+
+    it 'returns processorcount/2' do
+      expect(Facter.fact(:os_workers_heat_engine).value).to eq(4)
+    end
+  end
+
+  context 'with processorcount=64' do
+    before do
+      Facter.fact(:processorcount).stubs(:value).returns(64)
+    end
+
+    it 'returns a maximum of 24' do
+      expect(Facter.fact(:os_workers_heat_engine).value).to eq(24)
+    end
+  end
+end