以nova kilo版本为例
nova调度过程分析
之前创建虚拟机流程分析提到过：
#nova/scheduler/manager.py
class SchedulerManager(manager.Manager):
@messaging.expected_exceptions(exception.NoValidHost)
def select_destinations(self, context, request_spec, filter_properties):
'''driver其实就是调度算法实现，由配置文件决定，通常用的比较多的就是filter_scheduler，
对应filter_scheduler.py模块,该模块首先通过host_manager拿到所有的计算节点信息，
然后通过filters过滤掉不满足条件的计算节点，剩下的节点通过weigh方法计算权值，
最后选择权值高的作为候选计算节点返回。nova-scheduler进程结束。'''
dests = self.driver.select_destinations(context, request_spec,
filter_properties)
return jsonutils.to_primitive(dests)
driver在SchedulerManager 的__init__方法中定义
class SchedulerManager(manager.Manager):
def __init__(self, scheduler_driver=None, *args, **kwargs):
if not scheduler_driver:
scheduler_driver = CONF.scheduler_driver
#driver 是通过配置文件中的选项值指定的类来返回的对象
self.driver = importutils.import_object(scheduler_driver)
在nova的配置文件中：
scheduler_driver=nova.scheduler.filter_scheduler.FilterScheduler
继续往下分析：
#nova/scheduler/filter_scheduler.py
class FilterScheduler(driver.Scheduler):
def select_destinations(self, context, request_spec, filter_properties):
...
# 需要创建的 Instances 的数量
num_instances = request_spec['num_instances']
# 获取满足笫一次过滤条件的主机列表 List
selected_hosts = self._schedule(context, request_spec,
filter_properties)
# 当请求的 Instance 数量大于合适的主机数量时，不会创建 Instance 且输出错误信息
if len(selected_hosts) < num_instances and\
len(selected_hosts) >= min_instances:
...
elif len(selected_hosts) < min_instances:
...
dests = [dict(host=host.obj.host, nodename=host.obj.nodename,
limits=host.obj.limits) for host in selected_hosts]
...
return dests
def _schedule(self, context, request_spec, filter_properties):
...
#获取所有Hosts 状态,主要用来去除不活跃的节点
hosts = self._get_all_host_states(elevated)
#调用HostManager的get_filtered_hosts方法来选择可用的计算节点
hosts = self.host_manager.get_filtered_hosts(hosts,
filter_properties, index=num, context=context)
...
#通过 Weighed 选取最优 Host
weighed_hosts = self.host_manager.get_weighed_hosts(hosts,
filter_properties, context=context)
...
return selected_hosts
再来看看get_filtered_hosts的调用过程：
#nova/scheduler/host_manager.py
class HostManager(object):
def get_filtered_hosts(self, hosts, filter_properties,
filter_class_names=None, index=0, context=None):
...
if filter_class_names is None:
filters = self.default_filters
else:
filters = self._choose_host_filters(filter_class_names)
...
return self.filter_handler.get_filtered_objects(filters,
hosts, filter_properties, index, context=context)
def _choose_host_filters(self, filter_cls_names):
...
#将filter_cls_names封装成列表
if not isinstance(filter_cls_names, (list, tuple)):
filter_cls_names = [filter_cls_names]
good_filters = []
bad_filters = []
for filter_name in filter_cls_names:
if filter_name not in self.filter_obj_map:
if filter_name not in self.filter_cls_map:
bad_filters.append(filter_name)
continue
filter_cls = self.filter_cls_map[filter_name]
self.filter_obj_map[filter_name] = filter_cls()
good_filters.append(self.filter_obj_map[filter_name])
if bad_filters:
msg = ", ".join(bad_filters)
raise exception.SchedulerHostFilterNotFound(filter_name=msg)
return good_filters
def __init__(self):
self.filter_handler = filters.HostFilterHandler()
#__init__方法中调用get_matching_classes方法去加载nova.conf配置文件的scheduler_available_filters属性设置的fileter
filter_classes = self.filter_handler.get_matching_classes(
CONF.scheduler_available_filters)
self.filter_cls_map = {cls.__name__: cls for cls in filter_classes}
self.default_filters = self._choose_host_filters(self._load_filters())
def _load_filters(self):
return CONF.scheduler_default_filters
nova.conf中的相关配置如下：
scheduler_available_filters=nova.scheduler.filters.all_filters
scheduler_default_filters=RetryFilter,AvailabilityZoneFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter
总结一下_choose_host_filters的工作流程：
- 将filter_cls_names封装成列表
- 依次检查filter_cls_names中的所有可用的filter列表（个人理解，其检查过程就是判断scheduler_default_filters定义的filter能不能在nova/filter/下找到相关类）
- 返回可用filter列表
添加自定义filter
自定义一个filter类，specified_host_filter.py：
from oslo_log import log as logging
from nova.scheduler import filters
LOG = logging.getLogger(__name__)
#任何filter类必须继承filters.BaseHostFilter类
class SpecifiedHostFilter(filters.BaseHostFilter):
def __init__(self):
#通知成功加载SpecifiedHostFilter类
LOG.info("SpecifiedHostFilter is initialized!")
#host_passes是每个类必须实现的方法,host_state保存了询问的计算节点的信息
#filter_properties保存了一些帮助nvoa scheduler完成调度的信息
def host_passes(slef, host_state, filter_properties):
#获取客户端要求的计算节点主机名
scheduler_hints = filter_properties.get('scheduler_hints',{})
requested_host = scheduler_hints.get('requested_host',None)
#如果客户提供了要求的计算节点，则检查当前计算节点与客户要求的节点是否匹配
if requested_host:
return requested_host == host_state.host
#如果客户没有提供要求的计算节点，则返回真
return True
将自定义filter放在nova目录下，形成下面的目录结构:
├── scheduler
├── myproject
│ ├── __init__.py
│ ├── specified_host_filter.py
修改nova.conf配置文件，
scheduler_available_filters=nova.scheduler.filters.all_filters
scheduler_available_filters=nova.myproject.specified_host_filter.SpecifiedHostFilter
scheduler_default_filters=RetryFilter,AvailabilityZoneFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,SpecifiedHostFilter
重启nova-scheduler服务
客户端测试
使用rdo快速搭建openstack-allinone环境，详情见官网
在specified_host_filter.py中打断点后，停止nova-scheduler服务，手动启动scheduler服务：
/usr/bin/python /usr/bin/nova-scheduler --config-file /etc/nova/nova.conf --logfile /var/log/nova/nova-scheduler.log
创建一台虚拟机:
openstack server create --flavor m1.tiny --image cirros --nic net-id=4eace7c7-ec56-4e12-9a05-fc70a0887220 --security-group default ----hint requested_host=no-such-host test
执行到断点处：
(Pdb) l
8 def __init__(self):
9 LOG.info("SpecifiedHostFilter is initialized!")
10
11 def host_passes(slef, host_state, filter_properties):
12 import pdb; pdb.set_trace()
13 -> scheduler_hints = filter_properties.get('scheduler_hints',{})
14 requested_host = scheduler_hints.get('requested_host',None)
15 if requested_host:
16 return requested_host ==host_state.host
17 return True
[EOF]
Pdb) n
-> requested_host = scheduler_hints.get('requested_host',None)
(Pdb) p scheduler_hints
{u'requested_host': u'no-such-host'}
(Pdb) n
-> if requested_host:
(Pdb) n
-> return requested_host ==host_state.host
(Pdb) p requested_host
u'no-such-host'
(Pdb) p host_state.host
u'openstack'
因为我们传的’no-such-host’和可用的主机’openstack’不相等，所以日志中看到这样的消息：
2017-05-02 18:19:42.417 13453 INFO nova.myproject.specified_host_filter [-] SpecifiedHostFilter is initialized!
2017-05-02 18:21:54.628 13453 INFO nova.filters [req-d120d748-eb65-4b86-a5ed-22673ea76a52 00ce1cf60c3a4df2842437b5c23d35f6 67ee8dfa658e43b2b1a3d8108f624a95 - - -] Filter SpecifiedHostFilter returned 0 hosts
如果我们不传–hint参数 或者—-hint requested_host=openstack ,虚拟机创建以后状态为Active
