Avoid domain undefine on configuration update (#1496)

Calling undefine on a domain and recreating it can result in some edge
case errors where if the current capabilities of libvirt have been
reduced, it may not be possible to restore the old definition.

Instead switch to calling `domain_define` with the new definition and
check that the resulting libvirt domain definition has been updated in
the expected manner, otherwise report an error to the user.

Fixes: #949
Relates-to: #1329
Relates-to: #1027
Relates-to: #1371

spec/unit/action/start_domain_spec.rb

@@ -33,8 +33,7 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
       allow(servers).to receive(:get).and_return(domain)
 
       allow(logger).to receive(:debug)
-      expect(logger).to receive(:info)
-      expect(ui).to_not receive(:error)
+      allow(logger).to receive(:info)
 
       allow(libvirt_domain).to receive(:xml_desc).and_return(domain_xml)
 
@@ -43,23 +42,53 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
     end
 
     it 'should execute without changing' do
-      expect(libvirt_domain).to_not receive(:undefine)
+      expect(ui).to_not receive(:error)
+      expect(libvirt_client).to_not receive(:define_domain_xml)
       expect(libvirt_domain).to receive(:autostart=)
       expect(domain).to receive(:start)
 
       expect(subject.call(env)).to be_nil
     end
 
-    context 'when previously running default config' do
-      let(:test_file) { 'existing.xml' }
+    context 'when any setting changed' do
+      let(:vagrantfile_providerconfig) do
+        <<-EOF
+        libvirt.cpus = 2
+        EOF
+      end
 
-      it 'should execute without changing' do
-        expect(libvirt_domain).to_not receive(:undefine)
+      let(:updated_domain_xml) {
+        new_xml = domain_xml.dup
+        new_xml['<vcpu>1</vcpu>'] = '<vcpu>2</vcpu>'
+        new_xml
+      }
+
+      it 'should update the domain' do
+        expect(ui).to_not receive(:error)
         expect(libvirt_domain).to receive(:autostart=)
+        expect(connection).to receive(:define_domain).and_return(libvirt_domain)
+        expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
         expect(domain).to receive(:start)
 
         expect(subject.call(env)).to be_nil
       end
+
+      context 'when there is an error during update' do
+        it 'should skip attempting to start' do
+          expect(ui).to receive(:error)
+          expect(connection).to receive(:define_domain).and_raise(::Libvirt::Error)
+
+          expect { subject.call(env) }.to raise_error(VagrantPlugins::ProviderLibvirt::Errors::VagrantLibvirtError)
+        end
+      end
+
+      context 'when there is an interrupt' do
+        it 'should skip attempting to start' do
+          expect(connection).to receive(:define_domain).and_raise(Interrupt)
+
+          expect { subject.call(env) }.to raise_error(Interrupt)
+        end
+      end
     end
 
     context 'nvram' do
@@ -73,9 +102,10 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         let(:test_file) { 'existing.xml' }
         let(:updated_test_file) { 'existing_added_nvram.xml' }
 
-        it 'should undefine without passing flags' do
-          expect(libvirt_domain).to receive(:undefine).with(0)
-          expect(servers).to receive(:create).with(xml: updated_domain_xml)
+        it 'should add the nvram element' do
+          expect(ui).to_not receive(:error)
+          expect(connection).to receive(:define_domain).with(updated_domain_xml).and_return(libvirt_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -87,17 +117,16 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         let(:vagrantfile_providerconfig) do
           <<-EOF
           libvirt.loader = "/path/to/loader/file"
-          libvirt.nvram = "/path/to/nvram/file"
-          # change another setting to trigger the undefine/create
-          libvirt.cpus = 4
+          libvirt.nvram = "/path/to/nvram/file1"
           EOF
         end
         let(:test_file) { 'nvram_domain.xml' }
         let(:updated_test_file) { 'nvram_domain_other_setting.xml' }
 
-        it 'should set the flag to keep nvram' do
-          expect(libvirt_domain).to receive(:undefine).with(VagrantPlugins::ProviderLibvirt::Util::DomainFlags::VIR_DOMAIN_UNDEFINE_KEEP_NVRAM)
-          expect(servers).to receive(:create).with(xml: updated_domain_xml)
+        it 'should keep the XML element' do
+          expect(ui).to_not receive(:error)
+          expect(connection).to receive(:define_domain).with(updated_domain_xml).and_return(libvirt_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -108,9 +137,10 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
           let(:vagrantfile_providerconfig) { }
           let(:updated_test_file) { 'nvram_domain_removed.xml' }
 
-          it 'should set the flag to remove nvram' do
-            expect(libvirt_domain).to receive(:undefine).with(VagrantPlugins::ProviderLibvirt::Util::DomainFlags::VIR_DOMAIN_UNDEFINE_NVRAM)
-            expect(servers).to receive(:create).with(xml: updated_domain_xml)
+          it 'should delete the XML element' do
+            expect(ui).to_not receive(:error)
+            expect(connection).to receive(:define_domain).with(updated_domain_xml).and_return(libvirt_domain)
+            expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
             expect(libvirt_domain).to receive(:autostart=)
             expect(domain).to receive(:start)
 
@@ -132,9 +162,10 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         end
 
         it 'should modify the domain tpm_path' do
-          expect(libvirt_domain).to receive(:undefine)
+          expect(ui).to_not receive(:error)
           expect(logger).to receive(:debug).with('tpm config changed')
-          expect(servers).to receive(:create).with(xml: updated_domain_xml)
+          expect(connection).to receive(:define_domain).with(updated_domain_xml).and_return(libvirt_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -153,9 +184,10 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         end
 
         it 'should modify the domain tpm_path' do
-          expect(libvirt_domain).to receive(:undefine)
+          expect(ui).to_not receive(:error)
           expect(logger).to receive(:debug).with('tpm config changed')
-          expect(servers).to receive(:create).with(xml: updated_domain_xml)
+          expect(connection).to receive(:define_domain).with(updated_domain_xml).and_return(libvirt_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -175,6 +207,7 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         end
 
         it 'should execute without changing' do
+          expect(ui).to_not receive(:error)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -194,6 +227,7 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         end
 
         it 'should execute without changing' do
+          expect(ui).to_not receive(:error)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -213,9 +247,10 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         end
 
         it 'should modify the domain' do
-          expect(libvirt_domain).to receive(:undefine)
+          expect(ui).to_not receive(:error)
           expect(logger).to receive(:debug).with('tpm config changed')
-          expect(servers).to receive(:create).with(xml: updated_domain_xml)
+          expect(connection).to receive(:define_domain).with(updated_domain_xml).and_return(libvirt_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -235,8 +270,9 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
         end
 
         it 'should not modify the domain' do
+          expect(ui).to_not receive(:error)
           expect(logger).to_not receive(:debug).with('clock timers config changed')
-          expect(servers).to_not receive(:create)
+          expect(connection).to_not receive(:define_domain)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -252,10 +288,13 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
           EOF
         end
 
+        let(:updated_test_file) { 'clock_timer_rtc_tsc.xml' }
+
         it 'should modify the domain' do
-          expect(libvirt_domain).to receive(:undefine)
+          expect(ui).to_not receive(:error)
           expect(logger).to receive(:debug).with('clock timers config changed')
-          expect(servers).to receive(:create).with(xml: match(/<clock offset='utc'>\s*<timer name='rtc'\/>\s*<timer name='tsc'\/>\s*<\/clock>/))
+          expect(connection).to receive(:define_domain).with(match(/<clock offset='utc'>\s*<timer name='rtc'\/>\s*<timer name='tsc'\/>\s*<\/clock>/)).and_return(libvirt_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)
 
@@ -264,10 +303,13 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
       end
 
       context 'timers removed' do
+        let(:updated_test_file) { 'clock_timer_removed.xml' }
+
         it 'should modify the domain' do
-          expect(libvirt_domain).to receive(:undefine)
+          expect(ui).to_not receive(:error)
           expect(logger).to receive(:debug).with('clock timers config changed')
-          expect(servers).to receive(:create).with(xml: match(/<clock offset='utc'>\s*<\/clock>/))
+          expect(connection).to receive(:define_domain).with(match(/<clock offset='utc'>\s*<\/clock>/)).and_return(libvirt_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, updated_domain_xml)
           expect(libvirt_domain).to receive(:autostart=)
           expect(domain).to receive(:start)