Add breakpoint on bcast lag for testing

piker/data/_sampling.py

@@ -233,9 +233,11 @@ async def sample_and_broadcast(
             # thus other consumers still attached.
             subs = bus._subscribers[sym.lower()]
 
+            lags = 0
             for (stream, tick_throttle) in subs:
 
                 try:
+                    with trio.move_on_after(0.2) as cs:
                         if tick_throttle:
                             # this is a send mem chan that likely
                             # pushes to the ``uniform_rate_send()`` below.
@@ -244,6 +246,11 @@ async def sample_and_broadcast(
                         else:
                                 await stream.send({sym: quote})
 
+                    if cs.cancelled_caught:
+                        lags += 1
+                        if lags > 10:
+                            await tractor.breakpoint()
+
                 except (
                     trio.BrokenResourceError,
                     trio.ClosedResourceError