openstack关于libvirt相关代码的分析（一）
这段时间研究openstack+xen可惜资料太少，决定看一下源代码得了。
如果看过一篇关于启动Openstack中启动一个虚拟机的过程的文章的话，就一定知道有一个叫做Spawn instance的过程。
我使用的代码是nova-2012.2的版本。
下面我们看一下nova/virt/libvirt/connection.py文件。
"""
A connection to a hypervisor through libvirt.
Supports KVM, LXC, QEMU, UML, and XEN.
**Related Flags**
:libvirt_type: Libvirt domain type. Can be kvm, qemu, uml, xen
(default: kvm).
:libvirt_uri: Override for the default libvirt URI (depends on libvirt_type).
:libvirt_disk_prefix: Override the default disk prefix for the devices
attached to a server.
:rescue_image_id: Rescue ami image (None = original image).
:rescue_kernel_id: Rescue aki image (None = original image).
:rescue_ramdisk_id: Rescue ari image (None = original image).
:injected_network_template: Template file for injected network
:allow_same_net_traffic: Whether to allow in project network traffic
我们需要创建以个libvirt xml去新建一个实例。这将会涉及到其中的to_xml函数。
def to_xml(self, instance, network_info, image_meta=None, rescue=False,
block_device_info=None):
LOG.debug(_('Starting toXML method'), instance=instance)
conf = self.get_guest_config(instance, network_info, image_meta,
rescue, block_device_info)
xml = conf.to_xml()
LOG.debug(_('Finished toXML method'), instance=instance)
return xml
可以看到，它调用了一个叫get_guest_config的函数
def get_guest_config(self, instance, network_info, image_meta, rescue,
block_device_info=None):
block_device_mapping = driver.block_device_info_get_mapping(
block_device_info)
devs = []
# FIXME(vish): stick this in db
inst_type_id = instance['instance_type_id']
inst_type = instance_types.get_instance_type(inst_type_id)
guest = config.LibvirtConfigGuest()
guest.virt_type = FLAGS.libvirt_type
guest.name = instance['name']
guest.uuid = instance['uuid']
guest.memory = inst_type['memory_mb'] * 1024
guest.vcpus = inst_type['vcpus']
root_device_name = driver.block_device_info_get_root(block_device_info)
if root_device_name:
root_device = block_device.strip_dev(root_device_name)
else:
# NOTE(yamahata):
# for nova.api.ec2.cloud.CloudController.get_metadata()
root_device = self.default_root_device
db.instance_update(
nova_context.get_admin_context(), instance['id'],
{'root_device_name': '/dev/' + self.default_root_device})
if FLAGS.libvirt_type == "lxc":
guest.os_type = "exe"
guest.os_init_path = "/sbin/init"
guest.os_cmdline = "console=ttyS0"
elif FLAGS.libvirt_type == "uml":
guest.os_type = "uml"
guest.os_kernel = "/usr/bin/linux"
guest.os_root = root_device_name or "/dev/ubda"
else:
if FLAGS.libvirt_type == "xen":
guest.os_type = "linux"
guest.os_root = root_device_name or "/dev/xvda"
else:
guest.os_type = "hvm"
if rescue:
guest.os_kernel = os.path.join(FLAGS.instances_path,
instance['name'],
"kernel.rescue")
guest.os_initrd = os.path.join(FLAGS.instances_path,
instance['name'],
"ramdisk.rescue")
elif instance['kernel_id']:
guest.os_kernel = os.path.join(FLAGS.instances_path,
instance['name'],
"kernel")
if FLAGS.libvirt_type == "xen":
guest.os_cmdline = "ro"
else:
guest.os_cmdline = "root=%s console=ttyS0" % (
root_device_name or "/dev/vda",)
if instance['ramdisk_id']:
guest.os_initrd = os.path.join(FLAGS.instances_path,
instance['name'],
"ramdisk")
else:
guest.os_boot_dev = "hd"
if FLAGS.libvirt_type != "lxc" and FLAGS.libvirt_type != "uml":
guest.acpi = True
if FLAGS.libvirt_type == "lxc":
fs = config.LibvirtConfigGuestFilesys()
fs.type = "mount"
fs.source_dir = os.path.join(FLAGS.instances_path,
instance['name'],
"rootfs")
guest.add_device(fs)
else:
if FLAGS.use_cow_images:
driver_type = 'qcow2'
else:
driver_type = 'raw'
if image_meta and image_meta.get('disk_format') == 'iso':
root_device_type = 'cdrom'
else:
root_device_type = 'disk'
if FLAGS.libvirt_type == "uml":
ephemeral_disk_bus = "uml"
elif FLAGS.libvirt_type == "xen":
ephemeral_disk_bus = "xen"
else:
ephemeral_disk_bus = "virtio"
if rescue:
diskrescue = config.LibvirtConfigGuestDisk()
diskrescue.source_type = "file"
diskrescue.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"disk.rescue")
diskrescue.driver_format = driver_type
diskrescue.driver_cache = self.disk_cachemode
diskrescue.target_dev = self.default_root_device
diskrescue.target_bus = ephemeral_disk_bus
guest.add_device(diskrescue)
diskos = config.LibvirtConfigGuestDisk()
diskos.source_type = "file"
diskos.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"disk")
diskos.driver_format = driver_type
diskos.driver_cache = self.disk_cachemode
diskos.target_dev = self.default_second_device
diskos.target_bus = ephemeral_disk_bus
guest.add_device(diskos)
else:
ebs_root = self._volume_in_mapping(self.default_root_device,
block_device_info)
if not ebs_root:
diskos = config.LibvirtConfigGuestDisk()
diskos.source_type = "file"
diskos.source_device = root_device_type
diskos.driver_format = driver_type
diskos.driver_cache = self.disk_cachemode
diskos.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"disk")
diskos.target_dev = root_device
if root_device_type == "cdrom":
diskos.target_bus = "ide"
else:
diskos.target_bus = "virtio"
guest.add_device(diskos)
ephemeral_device = None
if not (self._volume_in_mapping(self.default_second_device,
block_device_info) or
0 in [eph['num'] for eph in
driver.block_device_info_get_ephemerals(
block_device_info)]):
if instance['ephemeral_gb'] > 0:
ephemeral_device = self.default_second_device
if ephemeral_device is not None:
disklocal = config.LibvirtConfigGuestDisk()
disklocal.source_type = "file"
disklocal.source_device = root_device_type
disklocal.driver_format = driver_type
disklocal.driver_cache = self.disk_cachemode
disklocal.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"disk.local")
disklocal.target_dev = ephemeral_device
disklocal.target_bus = ephemeral_disk_bus
guest.add_device(disklocal)
if ephemeral_device is not None:
swap_device = self.default_third_device
db.instance_update(
nova_context.get_admin_context(), instance['id'],
{'default_ephemeral_device':
'/dev/' + self.default_second_device})
else:
swap_device = self.default_second_device
for eph in driver.block_device_info_get_ephemerals(
block_device_info):
diskeph = config.LibvirtConfigGuestDisk()
diskeph.source_type = "block"
diskeph.source_device = root_device_type
diskeph.driver_format = driver_type
diskeph.driver_cache = self.disk_cachemode
diskeph.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
_get_eph_disk(eph))
diskeph.target_dev = block_device.strip_dev(
eph['device_name'])
diskeph.target_bus = ephemeral_disk_bus
guest.add_device(diskeph)
swap = driver.block_device_info_get_swap(block_device_info)
if driver.swap_is_usable(swap):
diskswap = config.LibvirtConfigGuestDisk()
diskswap.disk_type = "file"
diskswap.driver_format = driver_type
diskswap.driver_cache = self.disk_cachemode
diskswap.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"disk.swap")
diskswap.target_dev = block_device.strip_dev(
swap['device_name'])
diskswap.target_bus = ephemeral_disk_bus
guest.add_device(diskswap)
elif (inst_type['swap'] > 0 and
not self._volume_in_mapping(swap_device,
block_device_info)):
diskswap = config.LibvirtConfigGuestDisk()
diskswap.disk_type = "file"
diskswap.driver_format = driver_type
diskswap.driver_cache = self.disk_cachemode
diskswap.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"disk.swap")
diskswap.target_dev = swap_device
diskswap.target_bus = ephemeral_disk_bus
guest.add_device(diskswap)
db.instance_update(
nova_context.get_admin_context(), instance['id'],
{'default_swap_device': '/dev/' + swap_device})
for vol in block_device_mapping:
connection_info = vol['connection_info']
mountpoint = vol['mount_device']
cfg = self.volume_driver_method('connect_volume',
connection_info,
mountpoint)
guest.add_device(cfg)
if self._has_config_drive(instance):
diskconfig = config.LibvirtConfigGuestDisk()
diskconfig.source_type = "file"
diskconfig.driver_format = "raw"
diskconfig.driver_cache = self.disk_cachemode
diskconfig.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"disk.config")
diskconfig.target_dev = self.default_last_device
diskconfig.target_bus = ephemeral_disk_bus
guest.add_device(diskconfig)
for (network, mapping) in network_info:
cfg = self.vif_driver.plug(instance, network, mapping)
guest.add_device(cfg)
if FLAGS.libvirt_type == "qemu" or FLAGS.libvirt_type == "kvm":
# The QEMU 'pty' driver throws away any data if no
# client app is connected. Thus we can't get away
# with a single type=pty console. Instead we have
# to configure two separate consoles.
consolelog = config.LibvirtConfigGuestSerial()
consolelog.type = "file"
consolelog.source_path = os.path.join(FLAGS.instances_path,
instance['name'],
"console.log")
guest.add_device(consolelog)
consolepty = config.LibvirtConfigGuestSerial()
consolepty.type = "pty"
guest.add_device(consolepty)
else:
consolepty = config.LibvirtConfigGuestConsole()
consolepty.type = "pty"
guest.add_device(consolepty)
if FLAGS.vnc_enabled and FLAGS.libvirt_type not in ('lxc', 'uml'):
if FLAGS.use_usb_tablet:
tablet = config.LibvirtConfigGuestInput()
tablet.type = "tablet"
tablet.bus = "usb"
guest.add_device(tablet)
graphics = config.LibvirtConfigGuestGraphics()
graphics.type = "vnc"
graphics.keymap = FLAGS.vnc_keymap
graphics.listen = FLAGS.vncserver_listen
guest.add_device(graphics)
return guest