这里只关注Nova virt的spawn函数,glance、nova后端为ceph
nova/virt/libvirt/driver.py def spawn(self, context, instance, p_w_picpath_meta, injected_files, admin_password, network_info=None, block_device_info=None): p_w_picpath_meta = objects.ImageMeta.from_dict(p_w_picpath_meta) disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type, instance, p_w_picpath_meta, block_device_info) self._create_p_w_picpath(context, instance, # 虚拟机拉取glance p_w_picpath disk_info['mapping'], network_info=network_info, block_device_info=block_device_info, files=injected_files, admin_pass=admin_password) xml = self._get_guest_xml(context, instance, network_info, disk_info, p_w_picpath_meta, block_device_info=block_device_info, write_to_disk=True) self._create_domain_and_network(context, xml, instance, network_info, disk_info, block_device_info=block_device_info) LOG.debug("Instance is running", instance=instance) def _wait_for_boot(): """Called at an interval until the VM is running.""" state = self.get_info(instance).state if state == power_state.RUNNING: LOG.info(_LI("Instance spawned successfully."), instance=instance) raise loopingcall.LoopingCallDone() timer = loopingcall.FixedIntervalLoopingCall(_wait_for_boot) # loopingcall等待虚拟机running的状态 timer.start(interval=0.5).wait() nova/virt/libvirt/driver.py def _create_p_w_picpath(self, context, instance, disk_mapping, suffix='', disk_p_w_picpaths=None, network_info=None, block_device_info=None, files=None, admin_pass=None, inject_files=True, fallback_from_host=None): booted_from_volume = self._is_booted_from_volume( # 判断是不是boot_from_volume,boot_from_volume没有base p_w_picpath instance) if not booted_from_volume: root_fname = p_w_picpathcache.get_cache_fname(disk_p_w_picpaths, 'p_w_picpath_id') size = instance.root_gb * units.Gi if size == 0 or suffix == '.rescue': size = None backend = p_w_picpath('disk') if backend.SUPPORTS_CLONE: # 只有backend为rbd的才支持clone操作 def clone_fallback_to_fetch(*args, **kwargs): try: backend.clone(context, disk_p_w_picpaths['p_w_picpath_id']) # clone操作在nova/virt/libvirt/p_w_picpathbackend.py中class Rbd下 except exception.ImageUnacceptable: # 除p_w_picpath格式为raw和iso外的格式都抛异常 libvirt_utils.fetch_p_w_picpath(*args, **kwargs) fetch_func = clone_fallback_to_fetch else: fetch_func = libvirt_utils.fetch_p_w_picpath self._try_fetch_p_w_picpath_cache(backend, fetch_func, context, # 进入_try_fetch_p_w_picpath_cache函数 root_fname, disk_p_w_picpaths['p_w_picpath_id'], instance, size, fallback_from_host) 。。。。。。。。 # File injection only if needed, # 这里在OpenStack in Openstack环境下注入密码有坑,从nova-compute log中看到一直卡在create p_w_picpath过程, # 实际上是卡在密码注入过程。。。 elif inject_files and CONF.libvirt.inject_partition != -2: if booted_from_volume: LOG.warn(_LW('File injection into a boot from volume ' 'instance is not supported'), instance=instance) self._inject_data( # 注入相关的操作 instance, network_info, admin_pass, files, suffix) if CONF.libvirt.virt_type == 'uml': libvirt_utils.chown(p_w_picpath('disk').path, 'root') nova/virt/libvirt/p_w_picpathbackend.py def clone(self, context, p_w_picpath_id_or_uri): p_w_picpath_meta = IMAGE_API.get(context, p_w_picpath_id_or_uri, include_locations=True) locations = p_w_picpath_meta['locations'] LOG.debug('Image locations are: %(locs)s' % {'locs': locations}) if p_w_picpath_meta.get('disk_format') not in ['raw', 'iso']: # p_w_picpath格式判断, 所以ceph p_w_picpath格式最好是raw,这样走的ceph的clone reason = _('Image is not raw format') raise exception.ImageUnacceptable(p_w_picpath_id=p_w_picpath_id_or_uri, reason=reason) for location in locations: if self.driver.is_cloneable(location, p_w_picpath_meta): return self.driver.clone(location, self.rbd_name) # 调用nova/virt/libvirt/storage/rbd_utils.py reason = _('No p_w_picpath locations are accessible') raise exception.ImageUnacceptable(p_w_picpath_id=p_w_picpath_id_or_uri, reason=reason) nova/virt/libvirt/driver.py def _try_fetch_p_w_picpath_cache(self, p_w_picpath, fetch_func, context, filename, p_w_picpath_id, instance, size, fallback_from_host=None): try: p_w_picpath.cache(fetch_func=fetch_func, # 进入cache函数 context=context, filename=filename, p_w_picpath_id=p_w_picpath_id, user_id=instance.user_id, project_id=instance.project_id, size=size) except exception.ImageNotFound: if not fallback_from_host: raise LOG.debug("Image %(p_w_picpath_id)s doesn't exist anymore " "on p_w_picpath service, attempting to copy " "p_w_picpath from %(host)s", {'p_w_picpath_id': p_w_picpath_id, 'host': fallback_from_host}, instance=instance) def copy_from_host(target, max_size): libvirt_utils.copy_p_w_picpath(src=target, dest=target, host=fallback_from_host, receive=True) p_w_picpath.cache(fetch_func=copy_from_host, filename=filename) nova/virt/libvirt/p_w_picpathbackend.py def cache(self, fetch_func, filename, size=None, *args, **kwargs): """Creates p_w_picpath from template. Ensures that template and p_w_picpath not already exists. Ensures that base directory exists. Synchronizes on template fetching. :fetch_func: Function that creates the base p_w_picpath Should accept `target` argument. :filename: Name of the file in the p_w_picpath directory :size: Size of created p_w_picpath in bytes (optional) """ @utils.synchronized(filename, external=True, lock_path=self.lock_path) def fetch_func_sync(target, *args, **kwargs): # The p_w_picpath may have been fetched while a subsequent # call was waiting to obtain the lock. if not os.path.exists(target): # 如果不存在base p_w_picpath的话 fetch_func(target=target, *args, **kwargs) # fetch_func是clone_fallback_to_fetch base_dir = os.path.join(CONF.instances_path, CONF.p_w_picpath_cache_subdirectory_name) if not os.path.exists(base_dir): fileutils.ensure_tree(base_dir) base = os.path.join(base_dir, filename) if not self.check_p_w_picpath_exists() or not os.path.exists(base): self.create_p_w_picpath(fetch_func_sync, base, size, base p_w_picpath如果不存在的话,进入create_p_w_picpath *args, **kwargs) if (size and self.preallocate and self._can_fallocate() and os.access(self.path, os.W_OK)): utils.execute('fallocate', '-n', '-l', size, self.path) nova/virt/libvirt/p_w_picpathbackend.py def create_p_w_picpath(self, prepare_template, base, size, *args, **kwargs): if not self.check_p_w_picpath_exists(): prepare_template(target=base, max_size=size, *args, **kwargs) # prepare_template这里是fetch_func_sync # prepare_template() may have cloned the p_w_picpath into a new rbd # p_w_picpath already instead of downloading it locally if not self.check_p_w_picpath_exists(): # 如果走的是rbd clone操作,这里就不会用rbd import了 self.driver.import_p_w_picpath(base, self.rbd_name) self.verify_base_size(base, size) if size and size > self.get_disk_size(self.rbd_name): self.driver.resize(self.rbd_name, size)
总结: nova、glance后端为ceph,raw格式的p_w_picpath没有base p_w_picpath, qcow2格式还是有base p_w_picpath的,不过rbd import base p_w_picpath到pool后,可以把缓存的base p_w_picpath删除
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