On 9/10/14, 3:58 PM, "Devananda van der Veen" <devananda....@gmail.com>

>I'm going to assume that, for these benchmarks, you configured all the
>services optimally.

Sorry for any confusion; I am not trying to hide anything about the setup.
I thought I was pretty transparent about the way uWSGI, MongoDB, and Redis
were configured. I tried to stick to mostly default settings to keep
things simple, making it easier for others to reproduce/verify the results.

Is there further information about the setup that you were curious about
that I could provide? Was there a particular optimization that you didn’t
see that you would recommend?

>I'm not going to question why you didn't run tests
>with tens or hundreds of concurrent clients,

If you review the different tests, you will note that a couple of them
used at least 100 workers. That being said, I think we ought to try higher
loads in future rounds of testing.

>or why you only ran the
>tests for 10 seconds.

In Round 1 I did mention that i wanted to do a followup with a longer
duration. However, as I alluded to in the preamble for Round 2, I kept
things the same for the redis tests to compare with the mongo ones done

We’ll increase the duration in the next round of testing.

>Instead, I'm actually going to question how it is that, even with
>relatively beefy dedicated hardware (128 GB RAM in your storage
>nodes), Zaqar peaked at around 1,200 messages per second.

I went back and ran some of the tests and never saw memory go over ~20M
(as observed with redis-top) so these same results should be obtainable on
a box with a lot less RAM. Furthermore, the tests only used 1 CPU on the
Redis host, so again, similar results should be achievable on a much more
modest box.

FWIW, I went back and ran a couple scenarios to get some more data points.
First, I did one with 50 producers and 50 observers. In that case, the
single CPU on which the OS scheduled the Redis process peaked at 30%. The
second test I did was with 50 producers + 5 observers + 50 consumers
(which claim messages and delete them rather than simply page through
them). This time, Redis used 78% of its CPU. I suppose this should not be
surprising because the consumers do a lot more work than the observers.
Meanwhile, load on the web head was fairly high; around 80% for all 20
CPUs. This tells me that python and/or uWSGI are working pretty hard to
serve these requests, and there may be some opportunities to optimize that
layer. I suspect there are also some opportunities to reduce the number of
Redis operations and roundtrips required to claim a batch of messages.

The other thing to consider is that in these first two rounds I did not
test increasing amounts of load (number of clients performing concurrent
requests) and graph that against latency and throughput. Out of curiosity,
I just now did a quick test to compare the messages enqueued with 50
producers + 5 observers + 50 consumers vs. adding another 50 producer
clients and found that the producers were able to post 2,181 messages per
second while giving up only 0.3 ms.


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