Avoid 50msg/sec rate limit in monitoring router for DFK messages (#2303)
Avoid 50msg/sec rate limit in monitoring router for DFK messages (#2303)

The DFK can send many more messages than that under reasonable load,
and they queue up in the router process causing a lot of memory bloat.
i
I am able to reproduce this bloat with a tight loop submitting 200000 tasks.

before this patch:
There is a delay of loop freq (* some multiple) for every DFK message received,
if other non-dfk receives have to timeout.

with this patch:
the DFK receive loops tightly until there are no more messages to receive. on my
laptop this means the router uses hardly any extra memory (750mb compared to
550mb at router startup)
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