(POOLER-143) Add clone_target config change to API

This allows the user to change the cluster in which the targeted pool
will clone to. Upon configuration change, the thread will wake up and
execute the change within 1 second.

spec/unit/pool_manager_spec.rb

@@ -2390,6 +2390,59 @@ EOT
     end
   end
 
+  describe 'update_clone_target' do
+    let(:newtarget) { 'cluster2' }
+    let(:config) {
+      YAML.load(<<-EOT
+---
+:pools:
+  - name: #{pool}
+    clone_target: 'cluster1'
+EOT
+      )
+    }
+    let(:poolconfig) { config[:pools][0] }
+
+    context 'with a locked mutex' do
+
+      let(:mutex) { Mutex.new }
+      before(:each) do
+        mutex.lock
+        expect(subject).to receive(:pool_mutex).with(pool).and_return(mutex)
+      end
+
+      it 'should return nil' do
+        expect(subject.update_clone_target(poolconfig)).to be_nil
+      end
+    end
+
+    it 'should get the pool clone target configuration from redis' do
+      expect(redis).to receive(:hget).with('vmpooler__config__clone_target', pool)
+
+      subject.update_clone_target(poolconfig)
+    end
+
+    it 'should return when clone_target is not set in redis' do
+      expect(redis).to receive(:hget).with('vmpooler__config__clone_target', pool).and_return(nil)
+
+      expect(subject.update_clone_target(poolconfig)).to be_nil
+    end
+
+    it 'should return when no change in configuration is required' do
+      expect(redis).to receive(:hget).with('vmpooler__config__clone_target', pool).and_return('cluster1')
+
+      expect(subject.update_clone_target(poolconfig)).to be_nil
+    end
+
+    it 'should update the clone target' do
+      expect(redis).to receive(:hget).with('vmpooler__config__clone_target', pool).and_return(newtarget)
+
+      subject.update_clone_target(poolconfig)
+
+      expect(poolconfig['clone_target']).to eq(newtarget)
+    end
+  end
+
   describe "#execute!" do
     let(:config) {
       YAML.load(<<-EOT
@@ -2759,7 +2812,7 @@ EOT
 
       expect(subject).to receive(:sleep).exactly(2).times
       expect(subject).to receive(:time_passed?).with(:exit_by, Time).and_return(false, false, false, true)
-      
+
       subject.sleep_with_wakeup_events(loop_delay)
     end