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import gevent
from gevent import queue
from gevent.event import Event
from gevent import selectors
import uwsgi
_websocket_available = hasattr(uwsgi, 'websocket_handshake')
class Thread(gevent.Greenlet): # pragma: no cover
"""
This wrapper class provides gevent Greenlet interface that is compatible
with the standard library's Thread class.
"""
def __init__(self, target, args=[], kwargs={}):
super().__init__(target, *args, **kwargs)
def _run(self):
return self.run()
class uWSGIWebSocket(object): # pragma: no cover
"""
This wrapper class provides a uWSGI WebSocket interface that is
compatible with eventlet's implementation.
"""
def __init__(self, handler, server):
self.app = handler
self._sock = None
self.received_messages = []
def __call__(self, environ, start_response):
self._sock = uwsgi.connection_fd()
self.environ = environ
uwsgi.websocket_handshake()
self._req_ctx = None
if hasattr(uwsgi, 'request_context'):
# uWSGI >= 2.1.x with support for api access across-greenlets
self._req_ctx = uwsgi.request_context()
else:
# use event and queue for sending messages
self._event = Event()
self._send_queue = queue.Queue()
# spawn a select greenlet
def select_greenlet_runner(fd, event):
"""Sets event when data becomes available to read on fd."""
sel = selectors.DefaultSelector()
sel.register(fd, selectors.EVENT_READ)
try:
while True:
sel.select()
event.set()
except gevent.GreenletExit:
sel.unregister(fd)
self._select_greenlet = gevent.spawn(
select_greenlet_runner,
self._sock,
self._event)
self.app(self)
uwsgi.disconnect()
return '' # send nothing as response
def close(self):
"""Disconnects uWSGI from the client."""
if self._req_ctx is None:
# better kill it here in case wait() is not called again
self._select_greenlet.kill()
self._event.set()
def _send(self, msg):
"""Transmits message either in binary or UTF-8 text mode,
depending on its type."""
if isinstance(msg, bytes):
method = uwsgi.websocket_send_binary
else:
method = uwsgi.websocket_send
if self._req_ctx is not None:
method(msg, request_context=self._req_ctx)
else:
method(msg)
def _decode_received(self, msg):
"""Returns either bytes or str, depending on message type."""
if not isinstance(msg, bytes):
# already decoded - do nothing
return msg
# only decode from utf-8 if message is not binary data
type = ord(msg[0:1])
if type >= 48: # no binary
return msg.decode('utf-8')
# binary message, don't try to decode
return msg
def send(self, msg):
"""Queues a message for sending. Real transmission is done in
wait method.
Sends directly if uWSGI version is new enough."""
if self._req_ctx is not None:
self._send(msg)
else:
self._send_queue.put(msg)
self._event.set()
def wait(self):
"""Waits and returns received messages.
If running in compatibility mode for older uWSGI versions,
it also sends messages that have been queued by send().
A return value of None means that connection was closed.
This must be called repeatedly. For uWSGI < 2.1.x it must
be called from the main greenlet."""
while True:
if self._req_ctx is not None:
try:
msg = uwsgi.websocket_recv(request_context=self._req_ctx)
except IOError: # connection closed
self.close()
return None
return self._decode_received(msg)
else:
if self.received_messages:
return self.received_messages.pop(0)
# we wake up at least every 3 seconds to let uWSGI
# do its ping/ponging
event_set = self._event.wait(timeout=3)
if event_set:
self._event.clear()
# maybe there is something to send
msgs = []
while True:
try:
msgs.append(self._send_queue.get(block=False))
except gevent.queue.Empty:
break
for msg in msgs:
try:
self._send(msg)
except IOError:
self.close()
return None
# maybe there is something to receive, if not, at least
# ensure uWSGI does its ping/ponging
while True:
try:
msg = uwsgi.websocket_recv_nb()
except IOError: # connection closed
self.close()
return None
if msg: # message available
self.received_messages.append(
self._decode_received(msg))
else:
break
if self.received_messages:
return self.received_messages.pop(0)
_async = {
'thread': Thread,
'queue': queue.JoinableQueue,
'queue_empty': queue.Empty,
'event': Event,
'websocket': uWSGIWebSocket if _websocket_available else None,
'sleep': gevent.sleep,
}