xmlstream: purge send queue and pending tasks on session end

and keep track of slow tasks

slixmpp/xmlstream/xmlstream.py

@@ -12,7 +12,15 @@
     :license: MIT, see LICENSE for more details
 """
 
-from typing import Optional, Set, Callable, Any
+from typing import (
+    Any,
+    Callable,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Union,
+)
 
 import functools
 import logging
@@ -21,7 +29,7 @@ import ssl
 import weakref
 import uuid
 
-from asyncio import iscoroutinefunction, wait
+from asyncio import iscoroutinefunction, wait, Future
 
 import xml.etree.ElementTree as ET
 
@@ -230,6 +238,7 @@ class XMLStream(asyncio.BaseProtocol):
         self.add_event_handler('session_start', self._start_keepalive)
 
         self._run_filters = None
+        self.__slow_tasks: List[Future] = []
 
     @property
     def loop(self):
@@ -465,6 +474,7 @@ class XMLStream(asyncio.BaseProtocol):
         self.socket = None
         # Fire the events after cleanup
         if self.end_session_on_disconnect:
+            self._reset_sendq()
             self.event('session_end')
         self.event("disconnected", self.disconnect_reason or exception and exception.strerror)
 
@@ -937,6 +947,18 @@ class XMLStream(asyncio.BaseProtocol):
         """
         return xml
 
+    def _reset_sendq(self):
+        """Clear sending tasks on session end"""
+        # Cancel all pending slow send tasks
+        log.debug('Cancelling %d slow send tasks', len(self.__slow_tasks))
+        for slow_task in self.__slow_tasks:
+            slow_task.cancel()
+        self.__slow_tasks.clear()
+        # Purge pending stanzas
+        while not self.waiting_queue.empty():
+            discarded = self.waiting_queue.get_nowait()
+            log.debug('Discarded stanza: %s', discarded)
+
     async def _continue_slow_send(
             self,
             task: asyncio.Task,
@@ -950,6 +972,7 @@ class XMLStream(asyncio.BaseProtocol):
         :param set already_used: Filters already used on this outgoing stanza
         """
         data = await task
+        self.__slow_tasks.remove(task)
         for filter in self.__filters['out']:
             if filter in already_used:
                 continue
@@ -990,6 +1013,7 @@ class XMLStream(asyncio.BaseProtocol):
                                     timeout=1,
                                 )
                                 if pending:
+                                    self.slow_tasks.append(task)
                                     asyncio.ensure_future(
                                         self._continue_slow_send(
                                             task,