1. 概述
libvirt是基于KVM的上层封装，提供了操作KVM的生层接口，如虚拟机的生命周期(创建，删除，查看，管理)等，网络的管理和存储的管理。通过libvirt可以操作KVM，实现类似于virsh,virt-manager这些工具能够实现的功能，本文以查看当前hypervisor的所有instance为例，讲述通过libvirt模块，查看当前机器的虚拟机列表，关于libvirt的更多操作，如开机，关机，重启，网络管理，存储管理等操作，参考附件。
2. 实现代码
cat libvirt_vm.py #!/usr/bin/env python#_*_ coding:utf8 _*_#author:Happy#blog adddress: http://happylab.blog.51cto.com#来自Happy实验室import systry: import libvirt HAS_LIBVIRT = Trueexcept Exception: HAS_LIBVIRT = Falsedef is_virtual(): ''' 判断当前系统是否支持KVM虚拟化,不支持则退出 ''' if not HAS_LIBVIRT: sys.exit("current system are not support Virtualization") return 'virt' def get_conn(): ''' 获取libvirt的连接句柄,用于提供操作libivrt的接口 ''' if is_virtual() == 'virt': try: conn = libvirt.open('qemu:///system') except Exception as e: sys.exit(e) return conndef close_conn(conn): ''' 关闭libvirt的连接句柄 ''' return conn.close()def list_active_vms(): ''' 获取所有开机状态的instance,返回虚拟机的名字 ''' vms_list = [] conn = get_conn() domain_list = conn.listDomainsID() for id in domain_list: vms_list.append(conn.lookupByID(id).name()) close_conn(conn) return vms_listdef list_inactive_vms(): ''' 获取关机状态的instance，返回虚拟机的名字 ''' vms_list = [] conn = get_conn() for id in conn.listDefinedDomains(): vms_list.append(id) close_conn(conn) return vms_listdef list_all_vms(): ''' 获取所有的虚拟机 ''' vms = [] vms.extend(list_active_vms()) vms.extend(list_inactive_vms()) return vmsdef get_capability(): ''' 得到hypervisor的容量信息,返回格式为XML ''' conn = get_conn() capability = conn.getCapabilities() conn.close() return capabilitydef get_hostname(): ''' attain hypervisor's hostname ''' conn = get_conn() hostname = conn.getHostname() conn.close() return hostnamedef get_max_vcpus(): ''' 获取hypervisor支持虚拟机的最大CPU数 ''' conn = get_conn() max_vcpus = conn.getMaxVcpus(None) conn.close() return max_vcpusif __name__ == "__main__": print "当前主机%s的虚拟机列表:" % (get_hostname()) for vms in list_active_vms(): print vms 3. 测试
[root@ChuangYiYuan_10_16_2_19 ~]# python libvirt_vm.py 当前主机ChuangYiYuan_10_16_2_19的虚拟机列表:instance-0000006binstance-000001c1instance-000000b9instance-00000181instance-000001f5instance-000000cbinstance-0000007finstance-000000ebinstance-00000145instance-0000019binstance-000001b9instance-000000d7instance-0000012binstance-00000077instance-00000165instance-00000083
4. 总结
通过libvirt能够实现KVM的管理，libvirt提供了大部分管理KVM的接口，通过改接口，可以实现openstack底层的操作。
5. 附录
openstack关于libvirt底层的实现代码，供大家参考
"""Supports KVM, LXC, QEMU, UML, and XEN."""import errnoimport eventletimport functoolsimport globimport mmapimport osimport shutilimport socketimport sysimport tempfileimport threadingimport timeimport uuidclass LibvirtDriver(driver.ComputeDriver): capabilities = { "has_p_w_picpathcache": True, "supports_recreate": True, } def __init__(self, virtapi, read_only=False): super(LibvirtDriver, self).__init__(virtapi) global libvirt if libvirt is None: libvirt = __import__('libvirt') self._host_state = None self._initiator = None self._fc_wwnns = None self._fc_wwpns = None self._wrapped_conn = None self._wrapped_conn_lock = threading.Lock() self._caps = None self._vcpu_total = 0 self.read_only = read_only self.firewall_driver = firewall.load_driver( DEFAULT_FIREWALL_DRIVER, self.virtapi, get_connection=self._get_connection) vif_class = importutils.import_class(CONF.libvirt.vif_driver) self.vif_driver = vif_class(self._get_connection) self.volume_drivers = driver.driver_dict_from_config( CONF.libvirt.volume_drivers, self) self.dev_filter = pci_whitelist.get_pci_devices_filter() self._event_queue = None self._disk_cachemode = None self.p_w_picpath_cache_manager = p_w_picpathcache.ImageCacheManager() self.p_w_picpath_backend = p_w_picpathbackend.Backend(CONF.use_cow_p_w_picpaths) self.disk_cachemodes = {} self.valid_cachemodes = ["default", "none", "writethrough", "writeback", "directsync", "unsafe", ] for mode_str in CONF.libvirt.disk_cachemodes: disk_type, sep, cache_mode = mode_str.partition('=') if cache_mode not in self.valid_cachemodes: LOG.warn(_('Invalid cachemode %(cache_mode)s specified ' 'for disk type %(disk_type)s.'), {'cache_mode': cache_mode, 'disk_type': disk_type}) continue self.disk_cachemodes[disk_type] = cache_mode self._volume_api = volume.API() def _get_new_connection(self): # call with _wrapped_conn_lock held LOG.debug(_('Connecting to libvirt: %s'), self.uri()) wrapped_conn = None try: wrapped_conn = self._connect(self.uri(), self.read_only) finally: # Enabling the compute service, in case it was disabled # since the connection was successful. disable_reason = DISABLE_REASON_UNDEFINED if not wrapped_conn: disable_reason = 'Failed to connect to libvirt' self._set_host_enabled(bool(wrapped_conn), disable_reason) self._wrapped_conn = wrapped_conn try: LOG.debug(_("Registering for lifecycle events %s"), self) wrapped_conn.domainEventRegisterAny( None, libvirt.VIR_DOMAIN_EVENT_ID_LIFECYCLE, self._event_lifecycle_callback, self) except Exception as e: LOG.warn(_("URI %(uri)s does not support events: %(error)s"), {'uri': self.uri(), 'error': e}) try: LOG.debug(_("Registering for connection events: %s") % str(self)) wrapped_conn.registerCloseCallback(self._close_callback, None) except (TypeError, AttributeError) as e: # NOTE: The registerCloseCallback of python-libvirt 1.0.1+ # is defined with 3 arguments, and the above registerClose- # Callback succeeds. However, the one of python-libvirt 1.0.0 # is defined with 4 arguments and TypeError happens here. # Then python-libvirt 0.9 does not define a method register- # CloseCallback. LOG.debug(_("The version of python-libvirt does not support " "registerCloseCallback or is too old: %s"), e) except libvirt.libvirtError as e: LOG.warn(_("URI %(uri)s does not support connection" " events: %(error)s"), {'uri': self.uri(), 'error': e}) return wrapped_conn @staticmethod def uri(): if CONF.libvirt.virt_type == 'uml': uri = CONF.libvirt.connection_uri or 'uml:///system' elif CONF.libvirt.virt_type == 'xen': uri = CONF.libvirt.connection_uri or 'xen:///' elif CONF.libvirt.virt_type == 'lxc': uri = CONF.libvirt.connection_uri or 'lxc:///' else: uri = CONF.libvirt.connection_uri or 'qemu:///system' return uri @staticmethod def _connect(uri, read_only): def _connect_auth_cb(creds, opaque): if len(creds) == 0: return 0 LOG.warning( _("Can not handle authentication request for %d credentials") % len(creds)) raise exception.NovaException( _("Can not handle authentication request for %d credentials") % len(creds)) auth = [[libvirt.VIR_CRED_AUTHNAME, libvirt.VIR_CRED_ECHOPROMPT, libvirt.VIR_CRED_REALM, libvirt.VIR_CRED_PASSPHRASE, libvirt.VIR_CRED_NOECHOPROMPT, libvirt.VIR_CRED_EXTERNAL], _connect_auth_cb, None] try: flags = 0 if read_only: flags = libvirt.VIR_CONNECT_RO # tpool.proxy_call creates a native thread. Due to limitations # with eventlet locking we cannot use the logging API inside # the called function. return tpool.proxy_call( (libvirt.virDomain, libvirt.virConnect), libvirt.openAuth, uri, auth, flags) except libvirt.libvirtError as ex: LOG.exception(_("Connection to libvirt failed: %s"), ex) payload = dict(ip=LibvirtDriver.get_host_ip_addr(), method='_connect', reason=ex) rpc.get_notifier('compute').error(nova_context.get_admin_context(), 'compute.libvirt.error', payload) raise exception.HypervisorUnavailable(host=CONF.host) ''' 返回instance的个数，conn.numOfDomains()用于显示active的vm个数，conn.numOfDefinedDomains()则显示inactive的vm个数 ''' def get_num_instances(self): """Efficient override of base instance_exists method.""" return self._conn.numOfDomains() ''' 检查虚拟机是否存在，根据名字校验 ''' def instance_exists(self, instance_name): """Efficient override of base instance_exists method.""" try: self._lookup_by_name(instance_name) return True except exception.NovaException: return False ''' 查看libvirt active虚拟机的id号码，conn.numOfDomains()用于显示active虚拟机的个数，conn.numOfDefinedDomains()则用于显示inactive的虚拟机个数 ''' # TODO(Shrews): Remove when libvirt Bugzilla bug # 836647 is fixed. def list_instance_ids(self): if self._conn.numOfDomains() == 0: return [] return self._conn.listDomainsID() ''' 返回虚拟机列表的名字，调用list_instance_ids()函数，只是显示active虚拟机的名字，其中conn.lookupByID(ids).name()用于显示instance的名字 ''' def list_instances(self): names = [] for domain_id in self.list_instance_ids(): try: # We skip domains with ID 0 (hypervisors). if domain_id != 0: domain = self._lookup_by_id(domain_id) names.append(domain.name()) except exception.InstanceNotFound: # Ignore deleted instance while listing continue # extend instance list to contain also defined domains names.extend([vm for vm in self._conn.listDefinedDomains() if vm not in names]) return names ''' 查看instance的UUID号码，显示active+inactive状态的虚拟机的UUID号码，其中conn.lookupByID(ids).UUIDString()用于返回active instance的UUID号码 conn.lookupByName('name').UUIDString()则返回inactive虚拟机的UUID号 ''' def list_instance_uuids(self): uuids = set() for domain_id in self.list_instance_ids(): try: # We skip domains with ID 0 (hypervisors). if domain_id != 0: domain = self._lookup_by_id(domain_id) uuids.add(domain.UUIDString()) except exception.InstanceNotFound: # Ignore deleted instance while listing continue # extend instance list to contain also defined domains for domain_name in self._conn.listDefinedDomains(): try: uuids.add(self._lookup_by_name(domain_name).UUIDString()) except exception.InstanceNotFound: # Ignore deleted instance while listing continue return list(uuids) def plug_vifs(self, instance, network_info): """Plug VIFs into networks.""" for vif in network_info: self.vif_driver.plug(instance, vif) def unplug_vifs(self, instance, network_info, ignore_errors=False): """Unplug VIFs from networks.""" for vif in network_info: try: self.vif_driver.unplug(instance, vif) except exception.NovaException: if not ignore_errors: raise def _teardown_container(self, instance): inst_path = libvirt_utils.get_instance_path(instance) container_dir = os.path.join(inst_path, 'rootfs') container_root_device = instance.get('root_device_name') disk.teardown_container(container_dir, container_root_device) def _undefine_domain(self, instance): try: virt_dom = self._lookup_by_name(instance['name']) except exception.InstanceNotFound: virt_dom = None if virt_dom: try: try: virt_dom.undefineFlags( libvirt.VIR_DOMAIN_UNDEFINE_MANAGED_SAVE) except libvirt.libvirtError: LOG.debug(_("Error from libvirt during undefineFlags." " Retrying with undefine"), instance=instance) virt_dom.undefine() except AttributeError: # NOTE(vish): Older versions of libvirt don't support # undefine flags, so attempt to do the # right thing. try: if virt_dom.hasManagedSaveImage(0): virt_dom.managedSaveRemove(0) except AttributeError: pass virt_dom.undefine() except libvirt.libvirtError as e: with excutils.save_and_reraise_exception(): errcode = e.get_error_code() LOG.error(_('Error from libvirt during undefine. ' 'Code=%(errcode)s Error=%(e)s') % {'errcode': errcode, 'e': e}, instance=instance) def _cleanup_rbd(self, instance): pool = CONF.libvirt.p_w_picpaths_rbd_pool volumes = libvirt_utils.list_rbd_volumes(pool) pattern = instance['uuid'] def belongs_to_instance(disk): return disk.startswith(pattern) volumes = filter(belongs_to_instance, volumes) if volumes: libvirt_utils.remove_rbd_volumes(pool, *volumes) def _cleanup_lvm(self, instance): """Delete all LVM disks for given instance object.""" disks = self._lvm_disks(instance) if disks: libvirt_utils.remove_logical_volumes(*disks) @staticmethod def _get_disk_xml(xml, device): """Returns the xml for the disk mounted at device.""" try: doc = etree.fromstring(xml) except Exception: return None ret = doc.findall('./devices/disk') for node in ret: for child in node.getchildren(): if child.tag == 'target': if child.get('dev') == device: return etree.tostring(node) def _get_existing_domain_xml(self, instance, network_info, block_device_info=None): try: virt_dom = self._lookup_by_name(instance['name']) xml = virt_dom.XMLDesc(0) except exception.InstanceNotFound: disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type, instance, block_device_info) xml = self.to_xml(nova_context.get_admin_context(), instance, network_info, disk_info, block_device_info=block_device_info) return xml