Reduce message latency

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Reduce message latency

Lost
This is my test on my machine(Win7 64Bit)
runjava.bat com.rabbitmq.examples.PerfTest -y 1 -t "fanout"
starting consumer #0
starting producer #0
time: 1.004s, sent: 6500 msg/s, received: 3835 msg/s, min/avg/max latency: 56688/397343/461860 microseconds
time: 2.010s, sent: 8569 msg/s, received: 10593 msg/s, min/avg/max latency: 28248/152367/530374 microseconds
time: 3.019s, sent: 14056 msg/s, received: 14002 msg/s, min/avg/max latency: 23924/47356/92764 microseconds
time: 4.035s, sent: 14766 msg/s, received: 14806 msg/s, min/avg/max latency: 22454/43967/79098 microseconds
time: 5.035s, sent: 14974 msg/s, received: 15155 msg/s, min/avg/max latency: 22796/45204/75959 microseconds
time: 6.035s, sent: 15688 msg/s, received: 15597 msg/s, min/avg/max latency: 23521/44053/79210 microseconds
time: 7.037s, sent: 14494 msg/s, received: 14538 msg/s, min/avg/max latency: 9377/45745/87104 microseconds
time: 8.037s, sent: 15988 msg/s, received: 15242 msg/s, min/avg/max latency: 12745/40687/79064 microseconds
time: 9.042s, sent: 15166 msg/s, received: 15773 msg/s, min/avg/max latency: 20401/44023/83005 microseconds
time: 10.047s, sent: 15745 msg/s, received: 15857 msg/s, min/avg/max latency: 19345/41106/90384 microseconds
time: 11.047s, sent: 15168 msg/s, received: 15135 msg/s, min/avg/max latency: 18543/44455/71619 microseconds
time: 12.047s, sent: 15815 msg/s, received: 15911 msg/s, min/avg/max latency: 21204/39684/62742 microseconds
time: 13.055s, sent: 15140 msg/s, received: 14901 msg/s, min/avg/max latency: 20643/44745/88437 microseconds
time: 14.057s, sent: 15366 msg/s, received: 15530 msg/s, min/avg/max latency: 16885/43054/71122 microseconds
time: 15.057s, sent: 15345 msg/s, received: 15336 msg/s, min/avg/max latency: 9193/43760/85081 microseconds
time: 16.059s, sent: 15666 msg/s, received: 15498 msg/s, min/avg/max latency: 17244/44310/82039 microseconds
 
I found message avg latency is 40000~45000 microseconds, it need 40~45 milliseconds.
Is there any possible to reduce message latency?

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Re: Reduce message latency

Simon MacMullen-2
On 11/07/2014 2:49AM, Lost wrote:
> I found message avg latency is 40000~45000 microseconds, it need 40~45
> milliseconds.
> Is there any possible to reduce message latency?

Since you are not rate-limiting the producer, it's running as fast as it
can. Therefore all the internal message buffers inside RabbitMQ fill up,
and messages take longer to get through the broker.

You will find that if you reduce the message rate by 10-20% from the
maximum using the PerfTest -r parameter (e.g. "-r 14000" or so), latency
will drop considerably; I would expect latency of ~1ms to be acheivable
(obviously dependent on network ping time and the underlying OS).

But note that RabbitMQ doesn't give latency *guarantees*.

This blog post talks a bit more on the subject (towards the end):

http://www.rabbitmq.com/blog/2012/04/17/rabbitmq-performance-measurements-part-1/

Cheers, Simon

--
Simon MacMullen
RabbitMQ, Pivotal
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