Delay the handling of stanza for when the process is not busy

We use some dirty monkey-patching to add a idle_call() function to the
asyncio module. We then use that method to handle each received stanza only
when the event loop is not busy with some other IO (mainly, the standard
input)

slixmpp/xmlstream/asyncio.py

@@ -0,0 +1,32 @@
+"""
+A module that monkey patches the standard asyncio module to add an
+idle_call() method to the main loop. This method is used to execute a
+callback whenever the loop is not busy handling anything else. This means
+that it is a callback with lower priority than IO, timer, or even
+call_soon() ones. These callback are called only once each.
+"""
+
+import asyncio
+from asyncio import tasks, events
+
+def idle_call(self, callback):
+    if tasks.iscoroutinefunction(callback):
+        raise TypeError("coroutines cannot be used with idle_call()")
+    handle = events.Handle(callback, [], self)
+    self._idle.append(handle)
+
+def my_run_once(self):
+    if self._idle:
+        self._ready.append(events.Handle(lambda: None, (), self))
+    real_run_once(self)
+    if self._idle:
+        handle = self._idle.pop(0)
+        handle._run()
+
+cls = asyncio.get_event_loop().__class__
+
+cls._idle = []
+cls.idle_call = idle_call
+real_run_once = cls._run_once
+cls._run_once = my_run_once
+

slixmpp/xmlstream/resolver.py

@@ -8,7 +8,7 @@
     :license: MIT, see LICENSE for more details
 """
 
-import asyncio
+from slixmpp.xmlstream.asyncio import asyncio
 import socket
 import logging
 import random

slixmpp/xmlstream/xmlstream.py

@@ -12,7 +12,6 @@
     :license: MIT, see LICENSE for more details
 """
 
-import asyncio
 import functools
 import copy
 import logging
@@ -23,6 +22,7 @@ import uuid
 
 import xml.etree.ElementTree
 
+from slixmpp.xmlstream.asyncio import asyncio
 from slixmpp.xmlstream import tostring
 from slixmpp.xmlstream.stanzabase import StanzaBase, ElementBase
 from slixmpp.xmlstream.resolver import resolve, default_resolver
@@ -377,7 +377,8 @@ class XMLStream(object):
                 elif self.xml_depth == 1:
                     # A stanza is an XML element that is a direct child of
                     # the root element, hence the check of depth == 1
-                    self.__spawn_event(xml)
+                    asyncio.get_event_loop().\
+                        idle_call(functools.partial(self.__spawn_event, xml))
                     if self.xml_root is not None:
                         # Keep the root element empty of children to
                         # save on memory use.