怎样写 OpenStack Neutron 的 Extension （四）
上文说到需要在 /neutronclient/v2_0/myextension/extension.py 中分别定义五个 class：List/Show/Create/Delete/UpdateExtension。具体形式如下：import argparse
import logging
from neutronclient.neutron import v2_0 as neutronV20
from neutronclient.openstack.common.gettextutils import _
RESOURCE = 'myextension'
class ListExtension(neutronV20.ListCommand):
"""List extensions"""
resource = RESOURCE
log = logging.getLogger(__name__ + '.ListExtension')
list_columns = ['id', 'name']
class ShowExtension(neutronV20.ShowCommand):
"""Show information of a given extension."""
resource = RESOURCE
log = logging.getLogger(__name__ + '.ShowExtension')
class CreatePhysicalGateway(neutronV20.CreateCommand):
"""Create an extension."""
resource = RESOURCE
log = logging.getLogger(__name__ + '.CreateExtension')
def add_known_arguments(self, parser):
parser.add_argument(
'name', metavar='NAME',
help=_('Name of extension to create'))
def args2body(self, parsed_args):
body = {self.resource: {
'name': parsed_args.name}}
return body
class UpdateExtension(neutronV20.UpdateCommand):
"""update a given extension."""
resource = RESOURCE
log = logging.getLogger(__name__ + '.UpdateExtension')
class DeleteExtension(neutronV20.DeleteCommand):
"""Delete a given extension."""
resource = RESOURCE
log = logging.getLogger(__name__ + '.DeleteExtension')
这些 class 处在接受 CLI 命令的第一线，负责将命令转化成 API call。需要特别注意的是 CreateExtension 这个类，它有两个方法 add_known_arguments 和 args2body。前者定义了 CLI 命令接受哪些参数，后者规定如何将收到的参数打包起来。
这些参数打包之后就会发给 neutron 后台中我们自己定义的 plugin controller，但是如何发送这些参数还需要我们去 /neutronclient/v2_0/client.py 的 Client 类中设置：
首先是 uri 路径：
myextensions_path = "/myextensions"
myextension_path = "/myextensions/%s"
然后是每个操作所对应的传递方法：
@APIParamsCall
def list_myextensions(self, retrieve_all=True, **_params):
"""Fetches a list of all myextensions for a tenant."""
return self.list('myextensions', self.myextensions_path, retrieve_all,
**_params)
@APIParamsCall
def show_myextension(self, myextension, **_params):
"""Fetches information of a certain entry in myextension."""
return self.get(self.myextension_path % (myextension), params=_params)
@APIParamsCall
def create_myextension(self, body=None):
"""Creates a new myextension entry."""
return self.post(self.myextensions_path, body=body)
@APIParamsCall
def delete_myextension(self, myextension):
"""Deletes the specified myextension."""
return self.delete(self.myextension_path % (myextension))
@APIParamsCall
def update_myextension(self, myextension, body=None):
"""Updates a myextension."""
return self.put(self.myextension_path % (myextension), body=body)
如此一来，我们自己实现的 neutron plugin 就能够收到 CLI 发送过来的命令啦。
下一章再来说说怎么修改 OpenStack 的 Dashboard 来显示我们在 extension 中添加的新元素。
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