protocol/logging: workaround for asyncio's inability to detect connection closes on writes

artiq/protocols/logging.py

@@ -117,11 +117,19 @@ class LogForwarder(logging.Handler, TaskObject):
             try:
                 reader, writer = await asyncio.open_connection(self.host,
                                                                self.port)
+                detect_close = asyncio.ensure_future(reader.read(1))
                 writer.write(_init_string)
                 while True:
                     message = await self._queue.get() + "\n"
                     writer.write(message.encode())
                     await writer.drain()
+                    # HACK: detect connection termination through the completion
+                    # of a read operation. For some reason, write/drain operations
+                    # on a closed socket do not raise exceptions, but print
+                    # "asyncio:socket.send() raised exception."
+                    if detect_close.done():
+                        await asyncio.sleep(self.reconnect_timer)
+                        break
             except asyncio.CancelledError:
                 return
             except: