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Re: Low latency topics
Hi Bob,

Currently the broker does not hand out messages to consumers until they are
flushed to disk, this means the flush interval acts as a lower bound on
worst case latency. Setting that lower should fix the problem.

This problem has been eliminated in the next release, as both the blocking
on flush and the fetcher backoff have been eliminated--this should drop
latency to a few ms.

On Wed, Nov 7, 2012 at 5:55 PM, Bob Cotton <[EMAIL PROTECTED]> wrote:

> Hello,
> We have a low-volume topic (~75msgs/sec) for which we would like to have a
> low propagation delay from producer to consumer.
> We have 3 brokers, each with a default of 4 partitions each. for a total of
> 12 partitions.
> The producer is sync, without compression. There are 8 producers each
> producing 1/8 of the traffic.
> We are using the high-level java consumer, with 4 threads consuming the
> topic.
> We are wrapping the message with a custom Encoder/Decoder and record
> currentTimeMillis() on the sender, and do the same in the receiver, then
> record the propagation delay. All hosts are time synced with ntp.
> With the settings on the broker for flush messages and flush interval
> (unset, defaults to 500 msgs and 3000ms) the overall 95th percentile for
> propagation is 2,500ms.
> When we adjust the topic flush interval to 20ms, the 95th percentile drops
> to 1,700ms
> When we adjust the consumers "fetcher.backoff.ms" to 10, the 95th
> percentile drops to about 970ms.
> We would like this to be sub-500ms.
> We could run with less partitions and/or more consumer threads.
> Anything glaring about this config? anything we're missing?
> Thanks
> -Bob