issue #155: core: slightly rearrange how shutdown works

This eliminates Context.on_disconnect() and instead moves its
functionality to a signal wired up by ExternalContext.main().

It leaves mitogen.master.Context is in a better condition to move into
mitogen.parent where it belongs.

mitogen/core.py

@@ -832,10 +832,6 @@ class Stream(BasicStream):
         be called from any thread."""
         self._router.broker.defer(self._send, msg)
 
-    def on_disconnect(self, broker):
-        super(Stream, self).on_disconnect(broker)
-        self._router.on_disconnect(self, broker)
-
     def on_shutdown(self, broker):
         """Override BasicStream behaviour of immediately disconnecting."""
         _v and LOG.debug('%r.on_shutdown(%r)', self, broker)
@@ -862,9 +858,8 @@ class Context(object):
         return _unpickle_context, (self.context_id, self.name)
 
     def on_disconnect(self, broker):
-        _v and LOG.debug('Parent stream is gone, dying.')
+        _v and LOG.debug('%r.on_disconnect()', self)
         fire(self, 'disconnect')
-        broker.shutdown()
 
     def on_shutdown(self, broker):
         pass
@@ -1118,8 +1113,7 @@ class Router(object):
     def __repr__(self):
         return 'Router(%r)' % (self.broker,)
 
-    def on_disconnect(self, stream, broker):
-        """Invoked by Stream.on_disconnect()."""
+    def on_stream_disconnect(self, stream):
         for context in self._context_by_id.itervalues():
             stream_ = self._stream_by_id.get(context.context_id)
             if stream_ is stream:
@@ -1138,6 +1132,7 @@ class Router(object):
         self._stream_by_id[context.context_id] = stream
         self._context_by_id[context.context_id] = context
         self.broker.start_receive(stream)
+        listen(stream, 'disconnect', lambda: self.on_stream_disconnect(stream))
 
     def add_handler(self, fn, handle=None, persist=True, respondent=None):
         handle = handle or self._last_handle.next()
@@ -1359,6 +1354,10 @@ class ExternalContext(object):
             return
         self.broker.shutdown()
 
+    def _on_parent_disconnect(self):
+        _v and LOG.debug('%r: parent stream is gone, dying.', self)
+        self.broker.shutdown()
+
     def _setup_master(self, profiling, parent_id, context_id, in_fd, out_fd):
         self.profiling = profiling
         if profiling:
@@ -1378,6 +1377,7 @@ class ExternalContext(object):
         self.stream.accept(in_fd, out_fd)
         self.stream.receive_side.keep_alive = False
 
+        listen(self.stream, 'disconnect', self._on_parent_disconnect)
         listen(self.broker, 'shutdown', self._on_broker_shutdown)
         listen(self.broker, 'exit', self._on_broker_exit)
 

mitogen/master.py

@@ -644,13 +644,6 @@ class Broker(mitogen.core.Broker):
 class Context(mitogen.core.Context):
     via = None
 
-    def on_disconnect(self, broker):
-        """
-        Override base behaviour of triggering Broker shutdown on parent stream
-        disconnection.
-        """
-        mitogen.core.fire(self, 'disconnect')
-
     def call_async(self, fn, *args, **kwargs):
         LOG.debug('%r.call_async(%r, *%r, **%r)',
                   self, fn, args, kwargs)