devstack 安装出错 ERROR (ConnectionRefused): Unable to establish connection ..

在服务器（Red Hat Enterprise Linux Server release 7.1 (Maipo)）上，基于devstack搭建一个openstack开发环境，用于学习。

问题非常多，真是跋山涉水，百度 google齐上阵，经过3天的努力，还没有成功。

我看官网上说就2步，1.下载一个devstack，2../stack.sh就ok了，不知道是什么问题，为什么我问题这么多，大家和我一样么？

我这里出现错误的提示如下：

+++ nova flavor-list
ERROR (ConnectionRefused): Unable to establish connection to http://135.251.149.234:8774/v2.1/

我查了半天，实在没有思路，请大家帮忙看看。

我使用nova flavor-list --debug 命令观察,提示如下:

DEBUG (session:198) REQ: curl -g -i -X GET http://135.251.149.234:5000/v2.0 -H "Accept: application/json" -H "User-Agent: python-keystoneclient"
INFO (connectionpool:203) Starting new HTTP connection (1): 135.251.149.234
DEBUG (connectionpool:383) "GET /v2.0 HTTP/1.1" 200 341
DEBUG (session:215) RESP: [200] content-length: 341 vary: X-Auth-Token server: Apache/2.4.6 (Red Hat Enterprise Linux) connection: close date: Mon, 28 Sep 2015 14:38:2
1 GMT content-type: application/json x-openstack-request-id: req-52ccf6a4-e20e-47e0-9e78-341fa8580d37 RESP BODY: {"version": {"status": "stable", "updated": "2014-04-17T00:00:00Z", "media-types": [{"base": "application/json", "type": "application/vnd.openstack.identity
-v2.0+json"}], "id": "v2.0", "links": [{"href": "http://135.251.149.234:5000/v2.0/", "rel": "self"}, {"href": "http://docs.openstack.org/", "type": "text/html", "rel": "describedby"}]}}
DEBUG (v2:86) Making authentication request to http://135.251.149.234:5000/v2.0/tokens
INFO (connectionpool:238) Resetting dropped connection: 135.251.149.234
DEBUG (connectionpool:383) "POST /v2.0/tokens HTTP/1.1" 200 2928
DEBUG (session:198) REQ: curl -g -i -X GET http://135.251.149.234:8774/v2.1/ -H "User-Agent: python-novaclient" -H "Accept: application/json" -H "X-Auth-Token: {SHA1}5
2b5985a9ed26bf4df27872595aec97887dbd198"INFO (connectionpool:203) Starting new HTTP connection (1): 135.251.149.234
DEBUG (shell:905) Unable to establish connection to http://135.251.149.234:8774/v2.1/
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/novaclient/shell.py", line 903, in main
OpenStackComputeShell().main(argv)
  File "/usr/lib/python2.7/site-packages/novaclient/shell.py", line 737, in main
api_version = api_versions.discover_version(self.cs, api_version)
  File "/usr/lib/python2.7/site-packages/novaclient/api_versions.py", line 253, in discover_version
client)
  File "/usr/lib/python2.7/site-packages/novaclient/api_versions.py", line 235, in _get_server_version_range
version = client.versions.get_current()
  File "/usr/lib/python2.7/site-packages/novaclient/v2/versions.py", line 62, in get_current
return self._get_current()
  File "/usr/lib/python2.7/site-packages/novaclient/v2/versions.py", line 49, in _get_current
return self._get(url, "version")
  File "/usr/lib/python2.7/site-packages/novaclient/base.py", line 164, in _get
_resp, body = self.api.client.get(url)
  File "/usr/lib/python2.7/site-packages/keystoneclient/adapter.py", line 170, in get
return self.request(url, 'GET', **kwargs)
  File "/usr/lib/python2.7/site-packages/novaclient/client.py", line 91, in request
**kwargs)
  File "/usr/lib/python2.7/site-packages/keystoneclient/adapter.py", line 206, in request
resp = super(LegacyJsonAdapter, self).request(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/keystoneclient/adapter.py", line 95, in request
return self.session.request(url, method, **kwargs)
  File "/usr/lib/python2.7/site-packages/keystoneclient/utils.py", line 337, in inner
return func(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/keystoneclient/session.py", line 386, in request
resp = send(**kwargs)
  File "/usr/lib/python2.7/site-packages/keystoneclient/session.py", line 430, in _send_request
raise exceptions.ConnectionRefused(msg)
ConnectionRefused: Unable to establish connection to http://135.251.149.234:8774/v2.1/
ERROR (ConnectionRefused): Unable to establish connection to http://135.251.149.234:8774/v2.1/