Multiple Crawls (no scrapyd) signal handler Error (WebService, Address)

[Gallaecio]

Note: Originally reported by @thiagof at https://github.com/scrapy/scrapy/issues/1122

I'm running a long concurrent crawl from a shell script. There are many scrapy processes running in parallel.

Time to time one throw this errors

015-03-31 01:11:12-0300 [scrapy] ERROR: Error caught on signal handler: <bound method ?.stop_listening of <scrapy.webservice.WebService instance at 0x7f48362a4710>>
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1107, in _inlineCallbacks
        result = g.send(result)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/core/engine.py", line 300, in _finish_stopping_engine
        yield self.signals.send_catch_log_deferred(signal=signals.engine_stopped)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/signalmanager.py", line 23, in send_catch_log_deferred
        return signal.send_catch_log_deferred(*a, **kw)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/utils/signal.py", line 53, in send_catch_log_deferred
        *arguments, **named)
    --- <exception caught here> ---
      File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 140, in maybeDeferred
        result = f(*args, **kw)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/xlib/pydispatch/robustapply.py", line 54, in robustApply
        return receiver(*arguments, **named)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/webservice.py", line 96, in stop_listening
        self.port.stopListening()
    exceptions.AttributeError: WebService instance has no attribute 'port'

2015-03-31 01:12:16-0300 [scrapy] ERROR: Error caught on signal handler: <bound method ?.start_listening of <scrapy.webservice.WebService instance at 0x7fa8a733e710>>
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1107, in _inlineCallbacks
        result = g.send(result)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/core/engine.py", line 77, in start
        yield self.signals.send_catch_log_deferred(signal=signals.engine_started)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/signalmanager.py", line 23, in send_catch_log_deferred
        return signal.send_catch_log_deferred(*a, **kw)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/utils/signal.py", line 53, in send_catch_log_deferred
        *arguments, **named)
    --- <exception caught here> ---
      File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 140, in maybeDeferred
        result = f(*args, **kw)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/xlib/pydispatch/robustapply.py", line 54, in robustApply
        return receiver(*arguments, **named)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/webservice.py", line 90, in start_listening
        self.port = listen_tcp(self.portrange, self.host, self)
      File "/usr/local/lib/python2.7/dist-packages/scrapy/utils/reactor.py", line 14, in listen_tcp
        return reactor.listenTCP(x, factory, interface=host)
      File "/usr/local/lib/python2.7/dist-packages/twisted/internet/posixbase.py", line 495, in listenTCP
        p.startListening()
      File "/usr/local/lib/python2.7/dist-packages/twisted/internet/tcp.py", line 991, in startListening
        skt.listen(self.backlog)
      File "/usr/lib/python2.7/socket.py", line 224, in meth
        return getattr(self._sock,name)(*args)
    socket.error: [Errno 98] Address already in use

Had similar problem with telnet, but we disabled it.