Add test case for #96

tests/issue_96.py

@@ -0,0 +1,110 @@
+'''
+This is a test for issue #96:
+https://github.com/HyperionGray/trio-websocket/issues/96
+
+This is not a part of the automated tests, because its prone to a race condition
+and I have not been able to trigger it deterministically. Instead, this "test"
+connects multiple times, triggering the bug on average once or twice out of
+every 10 connections. The bug causes an uncaught exception which causes the
+script to crash.
+
+Note that the server handler and the client have `try/except ConnectionClosed`
+blocks. The bug in issue #96 is that the exception is raised in a background
+task, so it is not caught by the caller's try/except block. Instead, it crashes
+the nursery that the background task is running in.
+
+Here's an example run where the test fails:
+
+(venv) $ python tests/issue_96.py
+INFO:root:Connection 0
+INFO:root:Connection 1
+INFO:root:Connection 2
+INFO:root:Connection 3
+INFO:root:Connection 4
+INFO:root:Connection 5
+INFO:root:Connection 6
+INFO:root:Connection 7
+INFO:root:Connection 8
+INFO:root:Connection 9
+INFO:root:Connection 10
+INFO:root:Connection 11
+Traceback (most recent call last):
+  File "tests/issue_96.py", line 58, in <module>
+    trio.run(main)
+  File "/home/mhaase/code/trio-websocket/venv/lib/python3.6/site-packages/trio/_core/_run.py", line 1337, in run
+    raise runner.main_task_outcome.error
+  File "tests/issue_96.py", line 54, in main
+    nursery.cancel_scope.cancel()
+  File "/home/mhaase/code/trio-websocket/venv/lib/python3.6/site-packages/trio/_core/_run.py", line 397, in __aexit__
+    raise combined_error_from_nursery
+  File "/home/mhaase/code/trio-websocket/trio_websocket/_impl.py", line 327, in serve_websocket
+    await server.run(task_status=task_status)
+  File "/home/mhaase/code/trio-websocket/trio_websocket/_impl.py", line 1097, in run
+    await trio.sleep_forever()
+  File "/home/mhaase/code/trio-websocket/venv/lib/python3.6/site-packages/trio/_core/_run.py", line 397, in __aexit__
+    raise combined_error_from_nursery
+  File "/home/mhaase/code/trio-websocket/venv/lib/python3.6/site-packages/trio/_highlevel_serve_listeners.py", line 129, in serve_listeners
+    task_status.started(listeners)
+  File "/home/mhaase/code/trio-websocket/venv/lib/python3.6/site-packages/trio/_core/_run.py", line 397, in __aexit__
+    raise combined_error_from_nursery
+  File "/home/mhaase/code/trio-websocket/venv/lib/python3.6/site-packages/trio/_highlevel_serve_listeners.py", line 27, in _run_handler
+    await handler(stream)
+  File "/home/mhaase/code/trio-websocket/trio_websocket/_impl.py", line 1125, in _handle_connection
+    await connection.aclose()
+  File "/home/mhaase/code/trio-websocket/venv/lib/python3.6/site-packages/trio/_core/_run.py", line 397, in __aexit__
+    raise combined_error_from_nursery
+  File "/home/mhaase/code/trio-websocket/trio_websocket/_impl.py", line 927, in _reader_task
+    await handler(event)
+  File "/home/mhaase/code/trio-websocket/trio_websocket/_impl.py", line 811, in _handle_connection_closed_event
+    await self._write_pending()
+  File "/home/mhaase/code/trio-websocket/trio_websocket/_impl.py", line 968, in _write_pending
+    raise ConnectionClosed(self._close_reason) from None
+trio_websocket._impl.ConnectionClosed: <CloseReason code=1006 name=ABNORMAL_CLOSURE reason=None>
+
+You may need to modify the sleep duration to reliably trigger the bug on your
+system. On a successful test, it will make 1,000 connections without any
+uncaught exceptions.
+'''
+import functools
+import logging
+from random import random
+
+import trio
+from trio_websocket import connect_websocket, ConnectionClosed, serve_websocket
+
+
+logging.basicConfig(level=logging.INFO)
+
+
+async def handler(request):
+    ''' Reverse incoming websocket messages and send them back. '''
+    try:
+        ws = await request.accept()
+        await ws.send_message('issue96')
+        await trio.sleep(random()/1000)
+        await trio.aclose_forcefully(ws._stream)
+    except ConnectionClosed:
+        pass
+
+
+async def main():
+    async with trio.open_nursery() as nursery:
+        serve = functools.partial(serve_websocket, handler, 'localhost', 8000,
+            ssl_context=None)
+        await nursery.start(serve)
+
+        for n in range(1000):
+            logging.info('Connection %d', n)
+            try:
+                connection = await connect_websocket(nursery, 'localhost', 8000,
+                    '/', use_ssl=False)
+                await connection.get_message()
+                await connection.aclose()
+            except ConnectionClosed:
+                pass
+
+        nursery.cancel_scope.cancel()
+
+
+if __name__ == '__main__':
+    trio.run(main)