dashboard/moninj: use thread instead of asyncio UDP (#39)

artiq/dashboard/moninj.py

@@ -1,4 +1,5 @@
 import asyncio
+import threading
 import logging
 import socket
 import struct
@@ -273,34 +274,43 @@ class MonInj(TaskObject):
 
         self.subscriber = Subscriber("devices", self.init_devices)
         self.dm = None
-        self.transport = None
+        self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        # Never ceasing to disappoint, asyncio has an issue about UDP
+        # not being supported on Windows (ProactorEventLoop) open since 2014.
+        self.loop = asyncio.get_event_loop()
+        self.thread = threading.Thread(target=self.receiver_thread,
+                                       daemon=True)
+        self.thread.start()
 
     async def start(self, server, port):
-        loop = asyncio.get_event_loop()
-        await loop.create_datagram_endpoint(lambda: self,
-                                                 family=socket.AF_INET)
+        await self.subscriber.connect(server, port)
         try:
-            await self.subscriber.connect(server, port)
-            try:
-                TaskObject.start(self)
-            except:
-                await self.subscriber.close()
-                raise
+            TaskObject.start(self)
         except:
-            self.transport.close()
+            await self.subscriber.close()
             raise
 
     async def stop(self):
         await TaskObject.stop(self)
         await self.subscriber.close()
-        if self.transport is not None:
-            self.transport.close()
-            self.transport = None
+        try:
+            # This is required to make recvfrom terminate in the thread.
+            # On Linux, this raises "OSError: Transport endpoint is not
+            # connected", but still has the intended effect.
+            self.socket.shutdown(socket.SHUT_RDWR)
+        except OSError:
+            pass
+        self.socket.close()
+        self.thread.join()
 
-    def connection_made(self, transport):
-        self.transport = transport
+    def receiver_thread(self):
+        while True:
+            data, addr = self.socket.recvfrom(2048)
+            if addr is None:
+                break
+            self.loop.call_soon_threadsafe(self.datagram_received, data)
 
-    def datagram_received(self, data, addr):
+    def datagram_received(self, data):
         if self.dm is None:
             logger.debug("received datagram, but device manager "
                          "is not present yet")
@@ -330,12 +340,6 @@ class MonInj(TaskObject):
         except:
             logger.warning("failed to process datagram", exc_info=True)
 
-    def error_received(self, exc):
-        logger.warning("datagram endpoint error")
-
-    def connection_lost(self, exc):
-        self.transport = None
-
     def send_to_device(self, data):
         if self.dm is None:
             logger.debug("cannot sent to device yet, no device manager")
@@ -344,10 +348,8 @@ class MonInj(TaskObject):
         logger.debug("core device address: %s", ca)
         if ca is None:
             logger.warning("could not find core device address")
-        elif self.transport is None:
-            logger.warning("datagram endpoint not available")
         else:
-            self.transport.sendto(data, (ca, 3250))
+            self.socket.sendto(data, (ca, 3250))
 
     async def _do(self):
         while True:

artiq/frontend/artiq_dashboard.py

@@ -142,10 +142,9 @@ def main():
     atexit_register_coroutine(d_applets.stop)
     smgr.register(d_applets)
 
-    if os.name != "nt":
-        d_ttl_dds = moninj.MonInj()
-        loop.run_until_complete(d_ttl_dds.start(args.server, args.port_notify))
-        atexit_register_coroutine(d_ttl_dds.stop)
+    d_ttl_dds = moninj.MonInj()
+    loop.run_until_complete(d_ttl_dds.start(args.server, args.port_notify))
+    atexit_register_coroutine(d_ttl_dds.stop)
 
     d_schedule = schedule.ScheduleDock(
         status_bar, rpc_clients["schedule"], sub_clients["schedule"])
@@ -155,10 +154,11 @@ def main():
     smgr.register(logmgr)
 
     # lay out docks
-    right_docks = [d_explorer, d_shortcuts]
-    if os.name != "nt":
-        right_docks += [d_ttl_dds.ttl_dock, d_ttl_dds.dds_dock]
-    right_docks += [d_datasets, d_applets]
+    right_docks = [
+        d_explorer, d_shortcuts,
+        d_ttl_dds.ttl_dock, d_ttl_dds.dds_dock,
+        d_datasets, d_applets
+    ]
     main_window.addDockWidget(QtCore.Qt.RightDockWidgetArea, right_docks[0])
     for d1, d2 in zip(right_docks, right_docks[1:]):
         main_window.tabifyDockWidget(d1, d2)