Use broadcast chan for order client and avoid chan repacking

piker/clearing/_client.py

@@ -25,6 +25,7 @@ from dataclasses import dataclass, field
 
 import trio
 import tractor
+from tractor._broadcast import broadcast_receiver
 
 from ..data._source import Symbol
 from ..log import get_logger
@@ -123,10 +124,15 @@ def get_orders(
     global _orders
 
     if _orders is None:
+        size = 100
+        tx, rx = trio.open_memory_channel(size)
+        brx = broadcast_receiver(rx, size)
+
         # setup local ui event streaming channels for request/resp
         # streamging with EMS daemon
         _orders = OrderBook(
-            *trio.open_memory_channel(100),
+            _to_ems=tx,
+            _from_order_book=brx,
         )
 
     return _orders
@@ -157,24 +163,13 @@ async def relay_order_cmds_from_sync_code(
 
     """
     book = get_orders()
-    orders_stream = book._from_order_book
-
+    async with book._from_order_book.subscribe() as orders_stream:
         async for cmd in orders_stream:
-
-        print(cmd)
             if cmd['symbol'] == symbol_key:
-
-            # send msg over IPC / wire
                 log.info(f'Send order cmd:\n{pformat(cmd)}')
+                # send msg over IPC / wire
                 await to_ems_stream.send(cmd)
 
-        else:
-            # XXX BRUTAL HACKZORZES !!!
-            # re-insert for another consumer
-            # we need broadcast channelz...asap
-            # https://github.com/goodboy/tractor/issues/204
-            book._to_ems.send_nowait(cmd)
-
 
 @asynccontextmanager
 async def open_ems(