如果你打算在js中使用openstack接口(如jstack)，就会碰到js的跨域请求问题，解决方法是要在openstack api的response中加上Access-Control-Allow-Origin: *这样的头信息。
##反向代理 如果给api配置了反向代理，可以参考：http://enable-cors.org/server.html
##配置wsgi 几乎所有的openstack api都使用了wsgi服务，我们可以在wsgi这层设置CORS信息。
首先安装一个python模块
pip install wsgicors
###让Keystone支持CORS 编辑/etc/keystone/keystone-paste.ini，新增如下内容：
[filter:cors]
use = egg:wsgicors#middleware
policy = open
open_origin = *
open_headers = *
open_methods = *
open_maxage = 86400
然后，在每个pipeline的开头加上cors，例如：
[pipeline:public_api]
pipeline = cors stats_monitoring sizelimit url_normalize build_auth_context token_auth admin_token_auth xml_body_v2 json_body ec2_extension user_crud_extension public_service
[pipeline:admin_api]
pipeline = cors sizelimit url_normalize build_auth_context token_auth admin_token_auth xml_body_v2 json_body ec2_extension s3_extension crud_extension admin_service
[pipeline:api_v3]
pipeline = cors stats_reporting sizelimit url_normalize build_auth_context token_auth admin_token_auth xml_body_v3 json_body ec2_extension_v3 s3_extension simple_cert_extension revoke_extension service_v3
[pipeline:public_version_api]
pipeline = cors sizelimit url_normalize xml_body public_version_service
[pipeline:admin_version_api]
pipeline = cors sizelimit url_normalize xml_body admin_version_service
最后重启服务
service keystone restart
###让nova-api支持CORS 编辑/etc/nova/api-paste.ini,新增如下内容：
[filter:cors]
use = egg:wsgicors#middleware
policy = open
open_origin = *
open_headers = *
open_methods = *
open_maxage = 86400
然后，在每个pipeline的开头加上cors，例如：
[composite:openstack_compute_api_v2]
use = call:nova.api.auth:pipeline_factory
noauth = cors compute_req_id faultwrap sizelimit noauth ratelimit osapi_compute_app_v2
keystone = cors compute_req_id faultwrap sizelimit authtoken keystonecontext ratelimit osapi_compute_app_v2
keystone_nolimit = cors compute_req_id faultwrap sizelimit authtoken keystonecontext osapi_compute_app_v2
[composite:openstack_compute_api_v21]
use = call:nova.api.auth:pipeline_factory_v21
noauth = cors request_id faultwrap sizelimit noauth osapi_compute_app_v21
keystone = cors request_id faultwrap sizelimit authtoken keystonecontext osapi_compute_app_v21
[composite:openstack_compute_api_v3]
use = call:nova.api.auth:pipeline_factory_v21
noauth = cors request_id faultwrap sizelimit noauth_v3 osapi_compute_app_v3
keystone = cors request_id faultwrap sizelimit authtoken keystonecontext osapi_compute_app_v3
最后重启nova-api
service nova-api restart
