(DIO-2675) Undo pool size template overrides

This implements a delete method for pooltemplate and poolsize. The API
removes the override from Redis and then adds an entry in Redis that
causes the pool manager to wake up and process the removal of the
override.

To facilitate this, a new variable has been created in lib/vmpooler.rb
to hold a copy of the original / pre-override config. This supplemental
copy of the pools is then indexed for use as a reference.

When pool manager wakes up to process an override removal, it looks up
the pre-override value from the config via the new variables mentioned
above.

Just as with entering overrides, no restart is needed. Template and pool
size changes are logged so that anyone watching or reviewing the logs
can see what happened when. The new API endpoints also return values for
both the pre-revert and post-revert value.

spec/unit/pool_manager_spec.rb

@@ -3159,6 +3159,54 @@ EOT
       end
     end
 
+    describe 'with the undo_override wakeup option' do
+      let(:wakeup_option) {{
+        :undo_override => true,
+        :poolname => pool
+      }}
+
+      let(:wakeup_period) { -1 } # A negative number forces the wakeup evaluation to always occur
+
+      context 'when a undoing a template override is requested' do
+        before(:each) do
+          redis_connection_pool.with do |redis|
+            redis.sadd('vmpooler__pool__undo_template_override', pool)
+            allow(redis).to receive(:hget)
+          end
+        end
+
+        it 'should sleep until the undo override request is detected' do
+          redis_connection_pool.with do |redis|
+            expect(subject).to receive(:sleep).at_least(2).times
+            expect(subject).to receive(:sleep).at_most(3).times
+            expect(redis).to receive(:sismember).with('vmpooler__pool__undo_template_override', pool).and_return(false,false,true)
+            expect(redis).to receive(:sismember).with('vmpooler__pool__undo_size_override', pool).and_return(false,false)
+          end
+
+          subject.sleep_with_wakeup_events(loop_delay, wakeup_period, wakeup_option)
+        end
+      end
+
+      context 'when a undoing a size override is requested' do
+        before(:each) do
+          redis_connection_pool.with do |redis|
+            redis.sadd('vmpooler__pool__undo_size_override', pool)
+            allow(redis).to receive(:hget)
+          end
+        end
+
+        it 'should sleep until the undo override request is detected' do
+          redis_connection_pool.with do |redis|
+            expect(subject).to receive(:sleep).exactly(3).times
+            expect(redis).to receive(:sismember).with('vmpooler__pool__undo_template_override', pool).and_return(false,false,false)
+            expect(redis).to receive(:sismember).with('vmpooler__pool__undo_size_override', pool).and_return(false,false,true)
+          end
+
+          subject.sleep_with_wakeup_events(loop_delay, wakeup_period, wakeup_option)
+        end
+      end
+    end
+
     describe 'with the pending_vm wakeup option' do
       let(:wakeup_option) {{
         :pending_vm => true,
@@ -3477,6 +3525,54 @@ EOT
     end
   end
 
+  describe 'undo_override' do
+    let(:mutex) { Mutex.new }
+    let(:original_template) { 'templates/template1' }
+    let(:override_template) { 'templates/template2' }
+    let(:original_size) { 2 }
+    let(:override_size) { 10 }
+    let(:config) { YAML.load(<<-EOT
+---
+:config:
+  task_limit: 5
+:providers:
+  :mock:
+:pools:
+  - name: '#{pool}'
+    size: #{override_size}
+    template: '#{override_template}'
+:pool_index:
+  '#{pool}': 0
+:pools_at_startup:
+  - name: '#{pool}'
+    size: #{original_size}
+    template: '#{original_template}'
+EOT
+      )
+    }
+
+    before(:each) do
+      redis_connection_pool.with do |redis|
+        redis.sadd('vmpooler__pool__undo_template_override', pool)
+        redis.sadd('vmpooler__pool__undo_size_override', pool)
+        # allow(redis).to receive(:hget)
+      end
+    end
+
+    it 'should revert to the original template and pool size' do
+      redis_connection_pool.with do |redis|
+        expect(redis).to receive(:sismember).with('vmpooler__pool__undo_template_override', pool).and_return(true)
+        expect(redis).to receive(:srem).with('vmpooler__pool__undo_template_override', pool).and_return(true)
+        expect(subject).to receive(:update_pool_template).with(config[:pools][0], provider, original_template, override_template, redis)
+
+        expect(redis).to receive(:sismember).with('vmpooler__pool__undo_size_override', pool).and_return(true)
+        expect(redis).to receive(:srem).with('vmpooler__pool__undo_size_override', pool).and_return(true)
+      end
+
+      subject.undo_override(config[:pools][0], provider)
+    end
+  end
+
   describe '#create_inventory' do
 
     it 'should log an error if one occurs' do