resources: virt: Add a virt resource based on libvirt

This adds an initial implementation of a virt resource based on libvirt.
It is not complete and requires more testing. The initial skeleton was
written by nseps but was not merged. It was later cleaned up and merged
in its current form by purpleidea. Many thanks to nseps for getting this
going, and hopefully we'll get you contributing more in the future!

DOCUMENTATION.md

@@ -223,6 +223,7 @@ parameter with the [Noop](#Noop) resource.
 * [Pkg](#Pkg):  Manage system packages with PackageKit.
 * [Svc](#Svc): Manage system systemd services.
 * [Timer](#Timer): Manage system systemd services.
+* [Virt](#Virt): Manage virtual machines with libvirt.
 
 ###Exec
 
@@ -287,6 +288,10 @@ The service resource is still very WIP. Please help us my improving it!
 
 This resource needs better documentation. Please help us my improving it!
 
+###Virt
+
+The virt resource can manage virtual machines via libvirt.
+
 ##Usage and frequently asked questions
 (Send your questions as a patch to this FAQ! I'll review it, merge it, and
 respond by commit with the answer.)

examples/virt1.yaml

@@ -0,0 +1,11 @@
+---
+graph: mygraph
+resources:
+  virt:
+  - name: mgmt1
+    uri: 'qemu:///session'
+    cpus: 1
+    memory: 524288
+    state: shutoff
+    transient: true
+edges: []

examples/virt2.yaml

@@ -0,0 +1,11 @@
+---
+graph: mygraph
+resources:
+  virt:
+  - name: mgmt2
+    uri: 'qemu:///session'
+    cpus: 1
+    memory: 524288
+    state: shutoff
+    transient: false
+edges: []

examples/virt3.yaml

@@ -0,0 +1,11 @@
+---
+graph: mygraph
+resources:
+  virt:
+  - name: mgmt3
+    uri: 'qemu:///session'
+    cpus: 1
+    memory: 524288
+    state: running
+    transient: false
+edges: []

gconfig/gconfig.go

@@ -64,6 +64,7 @@ type GraphConfig struct {
 		Pkg   []*resources.PkgRes   `yaml:"pkg"`
 		Svc   []*resources.SvcRes   `yaml:"svc"`
 		Timer []*resources.TimerRes `yaml:"timer"`
+		Virt  []*resources.VirtRes  `yaml:"virt"`
 	} `yaml:"resources"`
 	Collector []collectorResConfig `yaml:"collect"`
 	Edges     []edgeConfig         `yaml:"edges"`

resources/virt.go

@@ -0,0 +1,735 @@
+// Mgmt
+// Copyright (C) 2013-2016+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package resources
+
+import (
+	"encoding/gob"
+	"fmt"
+	"log"
+	"math/rand"
+	"time"
+
+	"github.com/purpleidea/mgmt/event"
+	"github.com/purpleidea/mgmt/global"
+
+	"github.com/pkg/errors"
+	"github.com/rgbkrk/libvirt-go"
+)
+
+func init() {
+	gob.Register(&VirtRes{})
+}
+
+var (
+	libvirtInitialized = false
+)
+
+// VirtRes is a libvirt resource. A transient virt resource, which has its state
+// set to `shutoff` is one which does not exist. The parallel equivalent is a
+// file resource which removes a particular path.
+type VirtRes struct {
+	BaseRes    `yaml:",inline"`
+	URI        string             `yaml:"uri"`       // connection uri, eg: qemu:///session
+	State      string             `yaml:"state"`     // running, paused, shutoff
+	Transient  bool               `yaml:"transient"` // defined (false) or undefined (true)
+	CPUs       uint               `yaml:"cpus"`
+	Memory     uint64             `yaml:"memory"` // in KBytes
+	Boot       []string           `yaml:"boot"`   // boot order. values: fd, hd, cdrom, network
+	Disk       []diskDevice       `yaml:"disk"`
+	CDRom      []cdRomDevice      `yaml:"cdrom"`
+	Network    []networkDevice    `yaml:"network"`
+	Filesystem []filesystemDevice `yaml:"filesystem"`
+
+	conn   libvirt.VirConnection
+	absent bool // cached state
+}
+
+// NewVirtRes is a constructor for this resource. It also calls Init() for you.
+func NewVirtRes(name string, uri, state string, transient bool, cpus uint, memory uint64) *VirtRes {
+	obj := &VirtRes{
+		BaseRes: BaseRes{
+			Name: name,
+		},
+		URI:       uri,
+		State:     state,
+		Transient: transient,
+		CPUs:      cpus,
+		Memory:    memory,
+	}
+	obj.Init()
+	return obj
+}
+
+// Init runs some startup code for this resource.
+func (obj *VirtRes) Init() error {
+	if !libvirtInitialized {
+		// TODO: update if https://github.com/rgbkrk/libvirt-go/pull/115 gets merged.
+		if i := libvirt.EventRegisterDefaultImpl(); i != 0 {
+			return fmt.Errorf("EventRegisterDefaultImpl failed with: %d", i)
+		}
+		libvirtInitialized = true
+	}
+
+	obj.absent = (obj.Transient && obj.State == "shutoff") // machine shouldn't exist
+
+	obj.BaseRes.kind = "Virt"
+	return obj.BaseRes.Init() // call base init, b/c we're overriding
+}
+
+// Validate if the params passed in are valid data.
+func (obj *VirtRes) Validate() error {
+	return nil
+}
+
+// Watch is the primary listener for this resource and it outputs events.
+func (obj *VirtRes) Watch(processChan chan event.Event) error {
+	if obj.IsWatching() {
+		return nil
+	}
+	obj.SetWatching(true)
+	defer obj.SetWatching(false)
+	cuid := obj.converger.Register()
+	defer cuid.Unregister()
+
+	var startup bool
+	Startup := func(block bool) <-chan time.Time {
+		if block {
+			return nil // blocks forever
+			//return make(chan time.Time) // blocks forever
+		}
+		return time.After(time.Duration(500) * time.Millisecond) // 1/2 the resolution of converged timeout
+	}
+
+	conn, err := libvirt.NewVirConnection(obj.URI)
+	if err != nil {
+		return fmt.Errorf("Connection to libvirt failed with: %s", err)
+	}
+
+	eventChan := make(chan int) // TODO: do we need to buffer this?
+	errorChan := make(chan error)
+	exitChan := make(chan struct{})
+	defer close(exitChan)
+
+	// run libvirt event loop
+	// TODO: *trigger* EventRunDefaultImpl to unblock so it can shut down...
+	// at the moment this isn't a major issue because it seems to unblock in
+	// bursts every 5 seconds! we can do this by writing to an event handler
+	// in the meantime, terminating the program causes it to exit anyways...
+	go func() {
+		for {
+			// TODO: can we merge this into our main for loop below?
+			select {
+			case <-exitChan:
+				log.Printf("EventRunDefaultImpl exited!")
+				return
+			default:
+			}
+			//log.Printf("EventRunDefaultImpl started!")
+			// TODO: update if https://github.com/rgbkrk/libvirt-go/pull/115 gets merged.
+			if i := libvirt.EventRunDefaultImpl(); i != 0 {
+				errorChan <- fmt.Errorf("EventRunDefaultImpl failed with: %d", i)
+				return
+			}
+			//log.Printf("EventRunDefaultImpl looped!")
+		}
+	}()
+
+	callback := libvirt.DomainEventCallback(
+		func(c *libvirt.VirConnection, d *libvirt.VirDomain, eventDetails interface{}, f func()) int {
+			if lifecycleEvent, ok := eventDetails.(libvirt.DomainLifecycleEvent); ok {
+				domName, _ := d.GetName()
+				if domName == obj.GetName() {
+					eventChan <- lifecycleEvent.Event
+				}
+			} else if global.DEBUG {
+				log.Printf("%s[%s]: Event details isn't DomainLifecycleEvent", obj.Kind(), obj.GetName())
+			}
+			return 0
+		},
+	)
+	callbackID := conn.DomainEventRegister(
+		libvirt.VirDomain{},
+		libvirt.VIR_DOMAIN_EVENT_ID_LIFECYCLE,
+		&callback,
+		nil,
+	)
+	defer conn.DomainEventDeregister(callbackID)
+
+	var send = false
+	var exit = false
+	var dirty = false
+
+	for {
+		select {
+		case event := <-eventChan:
+			// TODO: shouldn't we do these checks in CheckApply ?
+			switch event {
+			case libvirt.VIR_DOMAIN_EVENT_DEFINED:
+				if obj.Transient {
+					dirty = true
+					send = true
+				}
+			case libvirt.VIR_DOMAIN_EVENT_UNDEFINED:
+				if !obj.Transient {
+					dirty = true
+					send = true
+				}
+			case libvirt.VIR_DOMAIN_EVENT_STARTED:
+				fallthrough
+			case libvirt.VIR_DOMAIN_EVENT_RESUMED:
+				if obj.State != "running" {
+					dirty = true
+					send = true
+				}
+			case libvirt.VIR_DOMAIN_EVENT_SUSPENDED:
+				if obj.State != "paused" {
+					dirty = true
+					send = true
+				}
+			case libvirt.VIR_DOMAIN_EVENT_STOPPED:
+				fallthrough
+			case libvirt.VIR_DOMAIN_EVENT_SHUTDOWN:
+				if obj.State != "shutoff" {
+					dirty = true
+					send = true
+				}
+			case libvirt.VIR_DOMAIN_EVENT_PMSUSPENDED:
+				fallthrough
+			case libvirt.VIR_DOMAIN_EVENT_CRASHED:
+				dirty = true
+				send = true
+			}
+
+		case err := <-errorChan:
+			cuid.SetConverged(false)
+			return fmt.Errorf("Unknown %s[%s] libvirt error: %s", obj.Kind(), obj.GetName(), err)
+
+		case event := <-obj.events:
+			cuid.SetConverged(false)
+			if exit, send = obj.ReadEvent(&event); exit {
+				return nil // exit
+			}
+
+		case <-cuid.ConvergedTimer():
+			cuid.SetConverged(true) // converged!
+			continue
+
+		case <-Startup(startup):
+			cuid.SetConverged(false)
+			send = true
+			dirty = true
+		}
+
+		if send {
+			startup = true // startup finished
+			send = false
+			// only invalid state on certain types of events
+			if dirty {
+				dirty = false
+				obj.isStateOK = false // something made state dirty
+			}
+			if exit, err := obj.DoSend(processChan, ""); exit || err != nil {
+				return err // we exit or bubble up a NACK...
+			}
+		}
+	}
+}
+
+// attrCheckApply performs the CheckApply functions for CPU, Memory and others.
+// This shouldn't be called when the machine is absent; it won't be found!
+func (obj *VirtRes) attrCheckApply(apply bool) (bool, error) {
+	var checkOK = true
+
+	dom, err := obj.conn.LookupDomainByName(obj.GetName())
+	if err != nil {
+		return false, errors.Wrapf(err, "conn.LookupDomainByName failed")
+	}
+
+	domInfo, err := dom.GetInfo()
+	if err != nil {
+		// we don't know if the state is ok
+		return false, errors.Wrapf(err, "domain.GetInfo failed")
+	}
+
+	// check memory
+	if domInfo.GetMemory() != obj.Memory {
+		checkOK = false
+		if !apply {
+			return false, nil
+		}
+		if err := dom.SetMemory(obj.Memory); err != nil {
+			return false, errors.Wrapf(err, "domain.SetMemory failed")
+		}
+		log.Printf("%s[%s]: Memory changed", obj.Kind(), obj.GetName())
+	}
+
+	// check cpus
+	if domInfo.GetNrVirtCpu() != uint16(obj.CPUs) { // TODO: should CPU's be uint or uint16 ?
+		checkOK = false
+		if !apply {
+			return false, nil
+		}
+		if err := dom.SetVcpus(obj.CPUs); err != nil {
+			return false, errors.Wrapf(err, "domain.SetVcpus failed")
+		}
+		log.Printf("%s[%s]: CPUs changed", obj.Kind(), obj.GetName())
+	}
+
+	return checkOK, nil
+}
+
+// domainCreate creates a transient or persistent domain in the correct state. It
+// doesn't check the state before hand, as it is a simple helper function.
+func (obj *VirtRes) domainCreate() (libvirt.VirDomain, bool, error) {
+
+	if obj.Transient {
+		var flag uint32
+		var state string
+		switch obj.State {
+		case "running":
+			flag = libvirt.VIR_DOMAIN_NONE
+			state = "started"
+		case "paused":
+			flag = libvirt.VIR_DOMAIN_START_PAUSED
+			state = "paused"
+		case "shutoff":
+			// a transient, shutoff machine, means machine is absent
+			return libvirt.VirDomain{}, true, nil // returned dom is invalid
+		}
+		dom, err := obj.conn.DomainCreateXML(obj.getDomainXML(), flag)
+		if err != nil {
+			return dom, false, err // returned dom is invalid
+		}
+		log.Printf("%s[%s]: Domain transient %s", state, obj.Kind(), obj.GetName())
+		return dom, false, nil
+	}
+
+	dom, err := obj.conn.DomainDefineXML(obj.getDomainXML())
+	if err != nil {
+		return dom, false, err // returned dom is invalid
+	}
+	log.Printf("%s[%s]: Domain defined", obj.Kind(), obj.GetName())
+
+	if obj.State == "running" {
+		if err := dom.Create(); err != nil {
+			return dom, false, err
+		}
+		log.Printf("%s[%s]: Domain started", obj.Kind(), obj.GetName())
+	}
+
+	if obj.State == "paused" {
+		if err := dom.CreateWithFlags(libvirt.VIR_DOMAIN_START_PAUSED); err != nil {
+			return dom, false, err
+		}
+		log.Printf("%s[%s]: Domain created paused", obj.Kind(), obj.GetName())
+	}
+
+	return dom, false, nil
+}
+
+// CheckApply checks the resource state and applies the resource if the bool
+// input is true. It returns error info and if the state check passed or not.
+func (obj *VirtRes) CheckApply(apply bool) (bool, error) {
+	log.Printf("%s[%s]: CheckApply(%t)", obj.Kind(), obj.GetName(), apply)
+
+	if obj.isStateOK { // cache the state
+		return true, nil
+	}
+
+	var err error
+	obj.conn, err = libvirt.NewVirConnection(obj.URI)
+	if err != nil {
+		return false, fmt.Errorf("Connection to libvirt failed with: %s", err)
+	}
+
+	var checkOK = true
+
+	dom, err := obj.conn.LookupDomainByName(obj.GetName())
+	if err == nil {
+		// pass
+	} else if virErr, ok := err.(libvirt.VirError); ok && virErr.Domain == libvirt.VIR_FROM_QEMU && virErr.Code == libvirt.VIR_ERR_NO_DOMAIN {
+		// domain not found
+		if obj.absent {
+			obj.isStateOK = true
+			return true, nil
+		}
+
+		if !apply {
+			return false, nil
+		}
+
+		var c = true
+		dom, c, err = obj.domainCreate() // create the domain
+		if err != nil {
+			return false, errors.Wrapf(err, "domainCreate failed")
+		} else if !c {
+			checkOK = false
+		}
+
+	} else {
+		return false, errors.Wrapf(err, "LookupDomainByName failed")
+	}
+	defer dom.Free()
+	// domain exists
+
+	domInfo, err := dom.GetInfo()
+	if err != nil {
+		// we don't know if the state is ok
+		return false, errors.Wrapf(err, "domain.GetInfo failed")
+	}
+	isPersistent, err := dom.IsPersistent()
+	if err != nil {
+		// we don't know if the state is ok
+		return false, errors.Wrapf(err, "domain.IsPersistent failed")
+	}
+	isActive, err := dom.IsActive()
+	if err != nil {
+		// we don't know if the state is ok
+		return false, errors.Wrapf(err, "domain.IsActive failed")
+	}
+
+	// check for persistence
+	if isPersistent == obj.Transient { // if they're different!
+		if !apply {
+			return false, nil
+		}
+		if isPersistent {
+			if err := dom.Undefine(); err != nil {
+				return false, errors.Wrapf(err, "domain.Undefine failed")
+			}
+			log.Printf("%s[%s]: Domain undefined", obj.Kind(), obj.GetName())
+		} else {
+			domXML, err := dom.GetXMLDesc(libvirt.VIR_DOMAIN_XML_INACTIVE)
+			if err != nil {
+				return false, errors.Wrapf(err, "domain.GetXMLDesc failed")
+			}
+			if _, err = obj.conn.DomainDefineXML(domXML); err != nil {
+				return false, errors.Wrapf(err, "conn.DomainDefineXML failed")
+			}
+			log.Printf("%s[%s]: Domain defined", obj.Kind(), obj.GetName())
+		}
+		checkOK = false
+	}
+
+	// check for valid state
+	domState := domInfo.GetState()
+	switch obj.State {
+	case "running":
+		if domState == libvirt.VIR_DOMAIN_RUNNING {
+			break
+		}
+		if domState == libvirt.VIR_DOMAIN_BLOCKED {
+			// TODO: what should happen?
+			return false, fmt.Errorf("Domain %s is blocked!", obj.GetName())
+		}
+		if !apply {
+			return false, nil
+		}
+		if isActive { // domain must be paused ?
+			if err := dom.Resume(); err != nil {
+				return false, errors.Wrapf(err, "domain.Resume failed")
+			}
+			checkOK = false
+			log.Printf("%s[%s]: Domain resumed", obj.Kind(), obj.GetName())
+			break
+		}
+		if err := dom.Create(); err != nil {
+			return false, errors.Wrapf(err, "domain.Create failed")
+		}
+		checkOK = false
+		log.Printf("%s[%s]: Domain created", obj.Kind(), obj.GetName())
+
+	case "paused":
+		if domState == libvirt.VIR_DOMAIN_PAUSED {
+			break
+		}
+		if !apply {
+			return false, nil
+		}
+		if isActive { // domain must be running ?
+			if err := dom.Suspend(); err != nil {
+				return false, errors.Wrapf(err, "domain.Suspend failed")
+			}
+			checkOK = false
+			log.Printf("%s[%s]: Domain paused", obj.Kind(), obj.GetName())
+			break
+		}
+		if err := dom.CreateWithFlags(libvirt.VIR_DOMAIN_START_PAUSED); err != nil {
+			return false, errors.Wrapf(err, "domain.CreateWithFlags failed")
+		}
+		checkOK = false
+		log.Printf("%s[%s]: Domain created paused", obj.Kind(), obj.GetName())
+
+	case "shutoff":
+		if domState == libvirt.VIR_DOMAIN_SHUTOFF || domState == libvirt.VIR_DOMAIN_SHUTDOWN {
+			break
+		}
+		if !apply {
+			return false, nil
+		}
+
+		if err := dom.Destroy(); err != nil {
+			return false, errors.Wrapf(err, "domain.Destroy failed")
+		}
+		checkOK = false
+		log.Printf("%s[%s]: Domain destroyed", obj.Kind(), obj.GetName())
+	}
+
+	if !apply {
+		return false, nil
+	}
+	// remaining apply portion
+
+	// mem & cpu checks...
+	if !obj.absent {
+		if c, err := obj.attrCheckApply(apply); err != nil {
+			return false, errors.Wrapf(err, "attrCheckApply failed")
+		} else if !c {
+			checkOK = false
+		}
+	}
+
+	if apply || checkOK {
+		obj.isStateOK = true
+	}
+	return checkOK, nil // w00t
+}
+
+func (obj *VirtRes) getDomainXML() string {
+	var b string
+	b += "<domain type='kvm'>" // start domain
+
+	b += fmt.Sprintf("<name>%s</name>", obj.GetName())
+	b += fmt.Sprintf("<memory unit='KiB'>%d</memory>", obj.Memory)
+	b += fmt.Sprintf("<vcpu>%d</vcpu>", obj.CPUs)
+
+	b += "<os>"
+	b += "<type>hvm</type>"
+	if obj.Boot != nil {
+		for _, boot := range obj.Boot {
+			b += fmt.Sprintf("<boot dev='%s'/>", boot)
+		}
+	}
+	b += fmt.Sprintf("</os>")
+
+	b += fmt.Sprintf("<devices>") // start devices
+	// TODO: use capabilities to determine emulator
+	//b += "<emulator>/usr/bin/kvm-spice</emulator>" // TODO: ?
+	b += "<emulator>/usr/bin/qemu-kvm</emulator>"
+
+	if obj.Disk != nil {
+		for i, disk := range obj.Disk {
+			b += fmt.Sprintf(disk.GetXML(i))
+		}
+	}
+
+	if obj.CDRom != nil {
+		for i, cdrom := range obj.CDRom {
+			b += fmt.Sprintf(cdrom.GetXML(i))
+		}
+	}
+
+	if obj.Network != nil {
+		for i, net := range obj.Network {
+			b += fmt.Sprintf(net.GetXML(i))
+		}
+	}
+
+	if obj.Filesystem != nil {
+		for i, fs := range obj.Filesystem {
+			b += fmt.Sprintf(fs.GetXML(i))
+		}
+	}
+
+	b += "<serial type='pty'><target port='0'/></serial>"
+	b += "<console type='pty'><target type='serial' port='0'/></console>"
+	b += "</devices>" // end devices
+	b += "</domain>"  // end domain
+	return b
+}
+
+type virtDevice interface {
+	GetXML(idx int) string
+}
+
+type diskDevice struct {
+	Source string `yaml:"source"`
+	Type   string `yaml:"type"`
+}
+
+type cdRomDevice struct {
+	Source string `yaml:"source"`
+	Type   string `yaml:"type"`
+}
+
+type networkDevice struct {
+	Name string `yaml:"name"`
+	MAC  string `yaml:"mac"`
+}
+
+type filesystemDevice struct {
+	Access   string `yaml:"access"`
+	Source   string `yaml:"source"`
+	Target   string `yaml:"target"`
+	ReadOnly bool   `yaml:"read_only"`
+}
+
+func (d *diskDevice) GetXML(idx int) string {
+	var b string
+	b += "<disk type='file' device='disk'>"
+	b += fmt.Sprintf("<driver name='qemu' type='%s'/>", d.Type)
+	b += fmt.Sprintf("<source file='%s'/>", d.Source)
+	b += fmt.Sprintf("<target dev='vd%s' bus='virtio'/>", (string)(idx+97)) // TODO: 26, 27... should be 'aa', 'ab'...
+	b += "</disk>"
+	return b
+}
+
+func (d *cdRomDevice) GetXML(idx int) string {
+	var b string
+	b += "<disk type='file' device='cdrom'>"
+	b += fmt.Sprintf("<driver name='qemu' type='%s'/>", d.Type)
+	b += fmt.Sprintf("<source file='%s'/>", d.Source)
+	b += fmt.Sprintf("<target dev='hd%s' bus='ide'/>", (string)(idx+97)) // TODO: 26, 27... should be 'aa', 'ab'...
+	b += "<readonly/>"
+	b += "</disk>"
+	return b
+}
+
+func (d *networkDevice) GetXML(idx int) string {
+	if d.MAC == "" {
+		d.MAC = randMAC()
+	}
+	var b string
+	b += "<interface type='network'>"
+	b += fmt.Sprintf("<mac address='%s'/>", d.MAC)
+	b += fmt.Sprintf("<source network='%s'/>", d.Name)
+	b += "</interface>"
+	return b
+}
+
+func (d *filesystemDevice) GetXML(idx int) string {
+	var b string
+	b += "<filesystem" // open
+	if d.Access != "" {
+		b += fmt.Sprintf(" accessmode='%s'", d.Access)
+	}
+	b += ">" // close
+	b += fmt.Sprintf("<source dir='%s'/>", d.Source)
+	b += fmt.Sprintf("<target dir='%s'/>", d.Target)
+	if d.ReadOnly {
+		b += "<readonly/>"
+	}
+	b += "</filesystem>"
+	return b
+}
+
+// VirtUID is the UID struct for FileRes.
+type VirtUID struct {
+	BaseUID
+}
+
+// GetUIDs includes all params to make a unique identification of this object.
+// Most resources only return one, although some resources can return multiple.
+func (obj *VirtRes) GetUIDs() []ResUID {
+	x := &VirtUID{
+		BaseUID: BaseUID{name: obj.GetName(), kind: obj.Kind()},
+		// TODO: add more properties here so we can link to vm dependencies
+	}
+	return []ResUID{x}
+}
+
+// GroupCmp returns whether two resources can be grouped together or not.
+func (obj *VirtRes) GroupCmp(r Res) bool {
+	_, ok := r.(*VirtRes)
+	if !ok {
+		return false
+	}
+	return false // not possible atm
+}
+
+// AutoEdges returns the AutoEdge interface. In this case no autoedges are used.
+func (obj *VirtRes) AutoEdges() AutoEdge {
+	return nil
+}
+
+// Compare two resources and return if they are equivalent.
+func (obj *VirtRes) Compare(res Res) bool {
+	switch res.(type) {
+	case *VirtRes:
+		res := res.(*VirtRes)
+		if !obj.BaseRes.Compare(res) { // call base Compare
+			return false
+		}
+
+		if obj.Name != res.Name {
+			return false
+		}
+		if obj.URI != res.URI {
+			return false
+		}
+		if obj.State != res.State {
+			return false
+		}
+		if obj.Transient != res.Transient {
+			return false
+		}
+		if obj.CPUs != res.CPUs {
+			return false
+		}
+		// TODO: can we skip the compare of certain properties such as
+		// Memory because this object (but with different memory) can be
+		// *converted* into the new version that has more/less memory?
+		// We would need to run some sort of "old struct update", to get
+		// the new values, but that's easy to add.
+		if obj.Memory != res.Memory {
+			return false
+		}
+		// TODO:
+		//if obj.Boot != res.Boot {
+		//	return false
+		//}
+		//if obj.Disk != res.Disk {
+		//	return false
+		//}
+		//if obj.CDRom != res.CDRom {
+		//	return false
+		//}
+		//if obj.Network != res.Network {
+		//	return false
+		//}
+		//if obj.Filesystem != res.Filesystem {
+		//	return false
+		//}
+	default:
+		return false
+	}
+	return true
+}
+
+// CollectPattern applies the pattern for collection resources.
+func (obj *VirtRes) CollectPattern(string) {
+}
+
+// randMAC returns a random mac address in the libvirt range.
+func randMAC() string {
+	rand.Seed(time.Now().UnixNano())
+	return "52:54:00" +
+		fmt.Sprintf(":%x", rand.Intn(255)) +
+		fmt.Sprintf(":%x", rand.Intn(255)) +
+		fmt.Sprintf(":%x", rand.Intn(255))
+}