After adding reset method in WSGIService class.
When SIGHUP signal is send to nova-api service, it stops all the nova-api processes 
and while restarting the nova-api processes, it throws 
error: [Errno 9] Bad file descriptor.

File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
    cb(*args, **kw)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
    result = function(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 635, in server
Traceback (most recent call last):
Traceback (most recent call last):
    serv = Server(sock, sock.getsockname(),
  File "/usr/lib/python2.7/socket.py", line 224, in meth
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
2014-06-26 20:38:34.240 INFO nova.wsgi [-] WSGI server has stopped.
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 346, in fire_timers
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
    cb(*args, **kw)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
    timer()
    result = function(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 635, in server
    timer()
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
    cb(*args, **kw)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
    serv = Server(sock, sock.getsockname(),
2014-06-26 20:38:34.241 INFO nova.wsgi [-] WSGI server has stopped.
    cb(*args, **kw)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
2014-06-26 20:38:34.241 INFO nova.wsgi [-] WSGI server has stopped.
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 346, in fire_timers
    result = function(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 635, in server
Traceback (most recent call last):
    result = function(*args, **kwargs)
    return getattr(self._sock,name)(*args)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 635, in server
Traceback (most recent call last):
    result = function(*args, **kwargs)
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 346, in fire_timers
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 346, in fire_timers
    serv = Server(sock, sock.getsockname(),
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    timer()
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
    timer()
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    timer()
    return getattr(self._sock,name)(*args)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
  File "/usr/lib/python2.7/socket.py", line 170, in _dummy
    cb(*args, **kw)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
    cb(*args, **kw)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
    result = function(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 635, in server
    result = function(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 635, in server
    serv = Server(sock, sock.getsockname(),
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    serv = Server(sock, sock.getsockname(),
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
  File "/usr/lib/python2.7/socket.py", line 170, in _dummy
    return getattr(self._sock,name)(*args)
    raise error(EBADF, 'Bad file descriptor')
    cb(*args, **kw)
  File "/usr/lib/python2.7/socket.py", line 170, in _dummy
error: [Errno 9] Bad file descriptor