Append broker name to symbols before quotes broadcast in sampler task

piker/data/_sampling.py

@@ -181,6 +181,7 @@ async def sample_and_broadcast(
     bus: '_FeedsBus',  # noqa
     shm: ShmArray,
     quote_stream: trio.abc.ReceiveChannel,
+    brokername: str,
     sum_tick_vlm: bool = True,
 
 ) -> None:
@@ -190,8 +191,7 @@ async def sample_and_broadcast(
     # iterate stream delivered by broker
     async for quotes in quote_stream:
         # TODO: ``numba`` this!
-        for sym, quote in quotes.items():
-
+        for broker_symbol, quote in quotes.items():
             # TODO: in theory you can send the IPC msg *before* writing
             # to the sharedmem array to decrease latency, however, that
             # will require at least some way to prevent task switching
@@ -255,7 +255,13 @@ async def sample_and_broadcast(
             # end up triggering backpressure which which will
             # eventually block this producer end of the feed and
             # thus other consumers still attached.
-            subs = bus._subscribers[sym.lower()]
+            subs = bus._subscribers[broker_symbol.lower()]
+
+            # NOTE: by default the broker backend doesn't append
+            # it's own "name" into the fqsn schema (but maybe it
+            # should?) so we have to manually generate the correct
+            # key here.
+            bsym = f'{broker_symbol}.{brokername}'
 
             lags = 0
             for (stream, tick_throttle) in subs:
@@ -266,7 +272,9 @@ async def sample_and_broadcast(
                             # this is a send mem chan that likely
                             # pushes to the ``uniform_rate_send()`` below.
                             try:
-                                stream.send_nowait((sym, quote))
+                                stream.send_nowait(
+                                    (bsym, quote)
+                                )
                             except trio.WouldBlock:
                                 ctx = getattr(stream, '_ctx', None)
                                 if ctx:
@@ -280,7 +288,9 @@ async def sample_and_broadcast(
                                         f'feed @ {tick_throttle} Hz'
                                     )
                         else:
-                            await stream.send({sym: quote})
+                            await stream.send(
+                                {bsym: quote}
+                            )
 
                     if cs.cancelled_caught:
                         lags += 1