執行openstack flavor list後，通過在/nova/api/openstack/compute/flavors.py中FlavorsController類detail()方法添加斷點，具體如下：

    def detail(self, req):
        """Return all flavors in detail."""
        import pydevd
        pydevd.settrace(‘localhost‘, port=12345, stdoutToServer=True, stderrToServer=True)
        limited_flavors 
 
= self._get_flavors(req)  #調用方法從數據庫裏獲取到flavors
        req.cache_db_flavors(limited_flavors)     #。。。
        return self._view_builder.detail(req, limited_flavors)  #_view_builder是一個class ViewBuilder(common.ViewBuilder)對象，在views/flavors.py文件中

可以獲取到，nova是如何查詢到flavors並返回給client。

首先，我們查看req請求包含的內容：

GET /compute/v2.1/flavors/detail HTTP/1.1
Accept: application
 
/json
Accept-Encoding: gzip, deflate
Connection: keep-alive
Content-Length: 0
Host: 192.168.72.192
User-Agent: python-novaclient
X-Auth-Token: gAAAAABacqw9UtQcB8_Mwcjp72aGSy0amSoOX7rj0TO1m1wehcY9Oz3Rcppc4i1iv59J49NGk3Mms-t9BuV0MmOEaQQFXbcr2ImnY6ATDbctEn8Ve13rbv1yUaIgqTKdK5X0oLMzyaWcs5ORqAj0eAB0McQOlvVa5MZvuFxbm8k3uPHKEmW71Ac
X
 
-Domain-Id: None
X-Domain-Name: None
X-Identity-Status: Confirmed
X-Is-Admin-Project: True
X-Project-Domain-Id: default
X-Project-Domain-Name: Default
X-Project-Id: 220a18a8c961468f93f1d5b81de9774f
X-Project-Name: demo
X-Role: Member,anotherrole
X-Roles: Member,anotherrole
X-Service-Catalog: [{"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192/compute/v2/220a18a8c961468f93f1d5b81de9774f"}], "type": "compute_legacy", "name": "nova_legacy"}, {"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192:9696/"}], "type": "network", "name": "neutron"}, {"endpoints": [{"adminURL": "http://192.168.72.192/identity", "region": "RegionOne", "publicURL": "http://192.168.72.192/identity"}], "type": "identity", "name": "keystone"}, {"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192/volume/v1/220a18a8c961468f93f1d5b81de9774f"}], "type": "volume", "name": "cinder"}, {"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192/placement"}], "type": "placement", "name": "placement"}, {"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192/volume/v3/220a18a8c961468f93f1d5b81de9774f"}], "type": "volumev3", "name": "cinderv3"}, {"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192/compute/v2.1"}], "type": "compute", "name": "nova"}, {"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192/volume/v2/220a18a8c961468f93f1d5b81de9774f"}], "type": "volumev2", "name": "cinderv2"}, {"endpoints": [{"region": "RegionOne", "publicURL": "http://192.168.72.192/image"}], "type": "image", "name": "glance"}]
X-Tenant: demo
X-Tenant-Id: 220a18a8c961468f93f1d5b81de9774f
X-Tenant-Name: demo
X-User: demo
X-User-Domain-Id: default
X-User-Domain-Name: Default
X-User-Id: 159ceecc04924edd95f698e28772929b
X-User-Name: demo

使用了GET方法，具體的url=/compute/v2.1/flavors/detail，X-Auth-Token應該是keystone給的token認證。X-***給出的是一些工程、租戶、用戶等相關的信息。然後，使用limited_flavors=self._get_flavors(req)獲取到flavors的信息，return self._view_builder.detail(req, limited_flavors)對返回的flavor信息做了進一步處理，滿足返回請求的需要。

本文的分析沒有關註wsgi框架中如何載入app，以及如何建立RESTFUL框架的問題，而是直接從請求APP入口去分析openstack組件將如何去響應各種請求。

關於不同請求是如何與相應app對應，在後續介紹。

執行openstack flavor list後nova組件接收請求