The problem presents itself when a JSON-RPC call triggers some event in core.
When this happens we have a thread outside of Tornado call `write_message`
interleaved with a potentially ongoing write if the JSON-RPC response.
To avoid this we now follow Tornado best practices and add callbacks to the
IOLoop to ensure that there isn't any interleaved access of Tornado state.
Adds some WebSocketHandler tests that actually connect using a WS client and
plugs a potential race condition.
Any call to write_message could fail, either due to WebSocketClosedError like
in the log below, or simply due to socket errors. To play it safe we catch all
errors and debug log that a broadcast failed.
2015-02-26 21:24:02,266 ERROR [HttpServer] /home/adamcik/dev/mopidy/mopidy/http/handlers.py:116
mopidy.http.handlers WebSocket request error: deque index out of range
2015-02-26 21:24:10,098 ERROR [HttpFrontend-11] build/bdist.linux-x86_64/egg/pykka/actor.py:268
pykka Unhandled exception in HttpFrontend (urn:uuid:e376bd95-c32e-4e17-ad20-7d0b3c0cf2b2):
Traceback (most recent call last):
File "build/bdist.linux-x86_64/egg/pykka/actor.py", line 200, in _actor_loop
response = self._handle_receive(message)
File "build/bdist.linux-x86_64/egg/pykka/actor.py", line 294, in _handle_receive
return callee(*message['args'], **message['kwargs'])
File ".../dev/mopidy/mopidy/http/actor.py", line 77, in on_event
on_event(name, **data)
File ".../dev/mopidy/mopidy/http/actor.py", line 84, in on_event
handlers.WebSocketHandler.broadcast(message)
File ".../dev/mopidy/mopidy/http/handlers.py", line 78, in broadcast
client.write_message(msg)
File ".../dev/mopidy-virtualenv/local/lib/python2.7/site-packages/tornado/websocket.py", line 183, in write_message
raise WebSocketClosedError()
WebSocketClosedError
By removing the http://... URL in the log output, we hopefully remove the
dubious connection between hostname/port configuration and the URL you'll
actually use to browse the Mopidy web server.
Example log output with this change:
...
INFO Starting Mopidy frontends: HttpFrontend, MpdFrontend
INFO HTTP server running at [::ffff:127.0.0.1]:6680
INFO MPD server running at [::ffff:127.0.0.1]:6600
