In our prod, we can reproduce this issue. Now, we have to hack the code to sleep a while. But I'm looking for a way to upstream it.

2015-04-23 23:52:40,450 10583 ERROR django.request Internal Server Error: /horizon/project/instances/
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python2.7/dist-packages/horizon/decorators.py", line 38, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/horizon/decorators.py", line 54, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/horizon/decorators.py", line 38, in dec
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/views/generic/base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/views/generic/base.py", line 87, in dispatch
    return handler(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/horizon/tables/views.py", line 154, in get
    handled = self.construct_tables()
  File "/usr/lib/python2.7/dist-packages/horizon/tables/views.py", line 145, in construct_tables
    handled = self.handle_table(table)
  File "/usr/lib/python2.7/dist-packages/horizon/tables/views.py", line 118, in handle_table
    data = self._get_data_dict()
  File "/usr/lib/python2.7/dist-packages/horizon/tables/views.py", line 181, in _get_data_dict
    self._data = {self.table_class._meta.name: self.get_data()}
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/dashboards/project/instances/views.py", line 92, in get_data
    exceptions.handle(self.request, ignore=True)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/dashboards/project/instances/views.py", line 89, in get_data
    images, more = api.glance.image_list_detailed(self.request)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/api/glance.py", line 93, in image_list_detailed
    images = list(images_iter)
  File "/usr/share/openstack-dashboard/openstack_dashboard/wsgi/../../openstack_dashboard/api/glance.py", line 82, in <genexpr>
    images_iter = (i for i in images_iter if ((i.is_public and '-OLD-'
  File "/usr/lib/python2.7/dist-packages/glanceclient/v1/images.py", line 174, in paginate
    images = self._list(url, "images")
  File "/usr/lib/python2.7/dist-packages/glanceclient/common/base.py", line 53, in _list
    resp, body = self.api.json_request('GET', url)
  File "/usr/lib/python2.7/dist-packages/glanceclient/common/http.py", line 266, in json_request
    resp, body_iter = self._http_request(url, method, **kwargs)
  File "/usr/lib/python2.7/dist-packages/glanceclient/common/http.py", line 226, in _http_request
    resp = conn.getresponse()
  File "/usr/lib/python2.7/httplib.py", line 1045, in getresponse
    response.begin()
  File "/usr/lib/python2.7/httplib.py", line 409, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python2.7/httplib.py", line 365, in _read_status
    line = self.fp.readline(_MAXLINE + 1)
  File "/usr/lib/python2.7/socket.py", line 476, in readline
    data = self._sock.recv(self._rbufsize)
WantReadError