martin,
thanks.
to the extent you can set an HWM, then there ought to be a way
of measuring how much of that is being used. sure, its an estimate
and not exact. but if i have the PUSHer being blocked because of one
client,
it would surely be good to know who that was. or if a client was
unexpectedly
slow at servicing requests.
in my case, because i have an anonymous herd of PUSHers feeding an
anonymous herd of PULLers (for which there is no pattern), i have
well-known
chokepoints (one per node in a cluster), and i can measure the
traffic flowing
through each chokepoint. thus, i can tell the first herd of PUSHers how
to statistically shape their traffic to keep per-node queues balanced.
arguably, this might be done inside 0mq, but as per the discussion
we had a while back on distribution policy, for now it seems wise
to let all that stuff sit above 0mq. (even for that, though, it would be
nice to be able to get an estimate of queue length.)
andrew
On Sep 7, 2010, at 7:35 AM, Martin Sustrik wrote:
Andrew,
No. There's no such API. It's not even obvious what the semantics
should be. Some messages are in 0MQ tx buffer, some are in TCP tx
buffer
or PGM tx buffer, some may be on the wire but not yet at the receiver.
Moreover, the whole system is in state of flux so any figure you would
get would be outdated already etc.
Martin
On 7/9/2010, "Andrew Hume" <[email protected]> wrote:
thanks!
is there an API to get the queue length?
On Sep 7, 2010, at 6:43 AM, Martin Sustrik wrote:
Andrew,
just checking:
is there any pattern that incorporates back-pressure?
that is, fair share but taking queue length into account?
Both req/rep and push/pull patterns do apply backpressure _if_
there's
high watermark set (ZMQ_HWM socket option) for the length of the
queue.
Martin
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Andrew Hume (best -> Telework) +1 732-886-1886
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Andrew Hume (best -> Telework) +1 732-886-1886
[email protected] (Work) +1 973-360-8651
AT&T Labs - Research; member of USENIX and LOPSA
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