+class AsyncAwaker(GanetiBaseAsyncoreDispatcher):
+ """A way to notify the asyncore loop that something is going on.
+
+ If an asyncore daemon is multithreaded when a thread tries to push some data
+ to a socket, the main loop handling asynchronous requests might be sleeping
+ waiting on a select(). To avoid this it can create an instance of the
+ AsyncAwaker, which other threads can use to wake it up.
+
+ """
+ def __init__(self, signal_fn=None):
+ """Constructor for AsyncAwaker
+
+ @type signal_fn: function
+ @param signal_fn: function to call when awaken
+
+ """
+ GanetiBaseAsyncoreDispatcher.__init__(self)
+ assert signal_fn == None or callable(signal_fn)
+ (self.in_socket, self.out_socket) = socket.socketpair(socket.AF_UNIX,
+ socket.SOCK_STREAM)
+ self.in_socket.setblocking(0)
+ self.in_socket.shutdown(socket.SHUT_WR)
+ self.out_socket.shutdown(socket.SHUT_RD)
+ self.set_socket(self.in_socket)
+ self.need_signal = True
+ self.signal_fn = signal_fn
+ self.connected = True
+
+ # this method is overriding an asyncore.dispatcher method
+ def handle_read(self):
+ utils.IgnoreSignals(self.recv, 4096)
+ if self.signal_fn:
+ self.signal_fn()
+ self.need_signal = True
+
+ # this method is overriding an asyncore.dispatcher method
+ def close(self):
+ asyncore.dispatcher.close(self)
+ self.out_socket.close()
+
+ def signal(self):
+ """Signal the asyncore main loop.
+
+ Any data we send here will be ignored, but it will cause the select() call
+ to return.
+
+ """
+ # Yes, there is a race condition here. No, we don't care, at worst we're
+ # sending more than one wakeup token, which doesn't harm at all.
+ if self.need_signal:
+ self.need_signal = False
+ self.out_socket.send("\0")
+
+