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。
怎样写 OpenStack Neutron 的 Extension （四）,布布扣,bubuko.com
怎样写 OpenStack Neutron 的 Extension （四）
原文：http://www.cnblogs.com/zhutianshi/p/3926240.html