More ems resiliency: discard broken client dialogs

piker/clearing/_ems.py

@@ -262,7 +262,15 @@ async def clear_dark_triggers(
                             f'pred for {oid} was already removed!?'
                         )
 
+                    try:
                         await ems_client_order_stream.send(msg)
+                    except (
+                        trio.ClosedResourceError,
+                    ):
+                        log.warning(
+                            f'client {ems_client_order_stream} stream is broke'
+                        )
+                        break
 
                 else:  # condition scan loop complete
                     log.debug(f'execs are {execs}')
@@ -572,8 +580,16 @@ async def translate_and_relay_brokerd_events(
 
             # fan-out-relay position msgs immediately by
             # broadcasting updates on all client streams
-            for client_stream in router.clients:
+            for client_stream in router.clients.copy():
+                try:
                     await client_stream.send(pos_msg)
+                except(
+                    trio.ClosedResourceError,
+                    trio.BrokenResourceError,
+                ):
+                    router.clients.remove(client_stream)
+                    log.warning(
+                        f'client for {client_stream} was already closed?')
 
             continue