ceilometer api 源码

介绍

版本：juno

流程

/usr/bin/ceilometer-api

import sys
from ceilometer.cmd.api import main
if name == “main“:
 sys.exit(main())

cmd/api.py

def main():
 service.prepare_service()
 srv = app.build_server()
 srv.serve_forever()

api/app.py

def build_server():
 app = load_app()
 …
 srv = simple_server.make_server(host, port, app,
 server_cls, get_handler_cls())
 …
 return srv

def load_app():
 # Build the WSGI app
 …
 return deploy.loadapp(“config:” + cfg_file)

api_paste.ini对应app_factory

def app_factory(global_config, **local_conf):
 return VersionSelectorApplication()

class VersionSelectorApplication(object):
 …
 self.v2 = setup_app(pecan_config=pc)
 …

def setup_app(pecan_config=None, extra_hooks=None):
 …
 app = pecan.make_app(
 pecan_config.app.root,
 static_root=pecan_config.app.static_root,
 template_path=pecan_config.app.template_path,
 debug=CONF.api.pecan_debug,
 force_canonical=getattr(pecan_config.app, ‘force_canonical’, True),
 hooks=app_hooks,
 wrap_app=middleware.ParsableErrorMiddleware,
 guess_content_type_from_ext=False
 )
 return app

这里用到了pecan。
pecan，一个轻量的web框架，主页http://pecan.readthedocs.org/
ceilometer中主要是用来构建restapi，主页中关于restapi部分的介绍,需要继承rest.RestController；
其中重要的部分URL Mapping：

pecan的配置文件api/config.py

…
app = {
 ‘root’: ‘ceilometer.api.controllers.root.RootController’,
 ‘modules’: [‘ceilometer.api’],
 ‘static_root’: ‘%(confdir)s/public’,
 ‘template_path’: ‘%(confdir)s/ceilometer/api/templates’,
}
…

ceilometer.api.controllers.root.RootController.py

class RootController(object):

 v2 = v2.V2Controller()

 @pecan.expose(generic=True, template=’index.html’)
 def index(self):
 # FIXME: Return version information
 return dict()

这里注意v2 = v2.V2Controller()，其中就写了很多的restapi
api/controllers/v2.py

class V2Controller(object):
 “”“Version 2 API controller root.”“”
 resources = ResourcesController()
 meters = MetersController()
 samples = SamplesController()
 alarms = AlarmsController()
 event_types = EventTypesController()
 events = EventsController()
 query = QueryController()
 capabilities = CapabilitiesController()

这里又加载各种对象的restapi
接下来就只分析其中一个，其他类似
这里又用到了wsme和wsmeext.pecan。
wsme即Web Services Made Easy，简化了REST Web服务的编写。
可以运行在另一个框架的顶层，如（Cornice、Flask、Pecan）等，这里就是运行在了pecan之上来更加简单的构建restapi，用法:
wsmeext.pecan.wsexpose(return_type, *arg_types, **options)

import wsmeext.pecan as wsme_pecan
…
class ResourcesController(rest.RestController):
 “””Works on resources.”””

 def _resource_links(self, resource_id, meter_links=1):
 links = [_make_link(‘self’, pecan.request.host_url, ‘resources’,
 resource_id)]
 if meter_links:
 for meter in pecan.request.storage_conn.get_meters(
 resource=resource_id):
 query = {‘field’: ‘resource_id’, ‘value’: resource_id}
 links.append(_make_link(meter.name, pecan.request.host_url,
 ‘meters’, meter.name, query=query))
 return links

 #这里的get_one对应的就是GET http://<your ip>:8777/v2/resources/<resource_id>
 #返回的为一个Resource类型
 #参数为unicode类型
 @wsme_pecan.wsexpose(Resource, unicode)
 def get_one(self, resource_id):
 “””Retrieve details about one resource. :param resource_id: The UUID of the resource. “””
 :param resource_id: The UUID of the resource.
 “””
 authorized_project = acl.get_limited_to_project(pecan.request.headers)
 resources = list(pecan.request.storage_conn.get_resources(
 resource=resource_id, project=authorized_project))
 if not resources:
 raise EntityNotFound(_(‘Resource’), resource_id)
 return Resource.from_db_and_links(resources[0],
 self._resource_links(resource_id))
 #这里的get_all对应的就是GET http://<your ip>:8777/v2/resources[?meter_links={meter_links}&
 #q.field={field}&q.op={operator}&q.type={type}&q.value={value}]
 #返回类型是包含Resource的序列
 #参数类型是包含Query的序列
 @wsme_pecan.wsexpose([Resource], [Query], int)
 def get_all(self, q=None, meter_links=1):
 “””Retrieve definitions of all of the resources. :param q: Filter rules for the resources to be returned. :param meter_links: option to include related meter links “””
 :param q: Filter rules for the resources to be returned.
 :param meter_links: option to include related meter links
 “””
 q = q or []
 kwargs = _query_to_kwargs(q, pecan.request.storage_conn.get_resources)
 resources = [
 Resource.from_db_and_links(r,
 self._resource_links(r.resource_id,
 meter_links))
 for r in pecan.request.storage_conn.get_resources(**kwargs)]
 return resources