1. 概述

libvirt是基于KVM的上層封裝，提供了操作KVM的生層接口，如虛擬機的生命周期(創建，刪除，查看，管理)等，網絡的管理和存儲的管理。通過libvirt可以操作KVM，實現類似于virsh,virt-manager這些工具能夠實現的功能，本文以查看當前hypervisor的所有instance為例，講述通過libvirt模塊，查看當前機器的虛擬機列表，關于libvirt的更多操作，如開機，關機，重啟，網絡管理，存儲管理等操作，參考附件。

2. 實現代碼cat?libvirt_vm.py

#!/usr/bin/env?python

#_*_?coding:utf8?_*_

#author:Happy

#blog?adddress:?http://happylab.blog.51cto.com

#來自Happy實驗室

import?sys

try:

import?libvirt

HAS_LIBVIRT?=?True

except?Exception:

HAS_LIBVIRT?=?False

def?is_virtual():

'''

判斷當前系統是否支持KVM虛擬化,不支持則退出

'''

if?not?HAS_LIBVIRT:

sys.exit("current?system?are?not?support?Virtualization")

return?'virt'

def?get_conn():

'''

獲取libvirt的連接句柄,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?conn

def?close_conn(conn):

'''

關閉libvirt的連接句柄

'''

return?conn.close()

def?list_active_vms():

'''

獲取所有開機狀態的instance,返回虛擬機的名字

'''

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_list

def?list_inactive_vms():

'''

獲取關機狀態的instance，返回虛擬機的名字

'''

vms_list?=?[]

conn?=?get_conn()

for?id?in?conn.listDefinedDomains():

vms_list.append(id)

close_conn(conn)

return?vms_list

def?list_all_vms():

'''

獲取所有的虛擬機

'''

vms?=?[]

vms.extend(list_active_vms())

vms.extend(list_inactive_vms())

return?vms

def?get_capability():

'''

得到hypervisor的容量信息,返回格式為XML

'''

conn?=?get_conn()

capability?=?conn.getCapabilities()

conn.close()

return?capability

def?get_hostname():

'''

attain?hypervisor's?hostname

'''

conn?=?get_conn()

hostname?=?conn.getHostname()

conn.close()

return?hostname

def?get_max_vcpus():

'''

獲取hypervisor支持虛擬機的最大CPU數

'''

conn?=?get_conn()

max_vcpus?=?conn.getMaxVcpus(None)

conn.close()

return?max_vcpus

if?__name__?==?"__main__":

print?"當前主機%s的虛擬機列表:"?%?(get_hostname())

for?vms?in?list_active_vms():

print?vms

3. 測試[root@ChuangYiYuan_10_16_2_19?~]#?python?libvirt_vm.py

當前主機ChuangYiYuan_10_16_2_19的虛擬機列表:

instance-0000006b

instance-000001c1

instance-000000b9

instance-00000181

instance-000001f5

instance-000000cb

instance-0000007f

instance-000000eb

instance-00000145

instance-0000019b

instance-000001b9

instance-000000d7

instance-0000012b

instance-00000077

instance-00000165

instance-00000083

4. 總結

通過libvirt能夠實現KVM的管理，libvirt提供了大部分管理KVM的接口，通過改接口，可以實現openstack底層的操作。

5. 附錄

openstack關于libvirt底層的實現代碼，供大家參考"""

Supports?KVM,?LXC,?QEMU,?UML,?and?XEN.

"""

import?errno

import?eventlet

import?functools

import?glob

import?mmap

import?os

import?shutil

import?socket

import?sys

import?tempfile

import?threading

import?time

import?uuid

class?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的個數，conn.numOfDomains()用于顯示active的vm個數，conn.numOfDefinedDomains()則顯示inactive的vm個數

'''

def?get_num_instances(self):

"""Efficient?override?of?base?instance_exists?method."""

return?self._conn.numOfDomains()

'''

檢查虛擬機是否存在，根據名字校驗

'''

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虛擬機的id號碼，conn.numOfDomains()用于顯示active虛擬機的個數，conn.numOfDefinedDomains()則用于顯示inactive的虛擬機個數

'''

#?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()

'''

返回虛擬機列表的名字，調用list_instance_ids()函數，只是顯示active虛擬機的名字，其中conn.lookupByID(ids).name()用于顯示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號碼，顯示active+inactive狀態的虛擬機的UUID號碼，其中conn.lookupByID(ids).UUIDString()用于返回active?instance的UUID號碼

conn.lookupByName('name').UUIDString()則返回inactive虛擬機的UUID號

'''

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

總結

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