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On 30/06/14 21:34, Alexei Kornienko wrote:
> Hello,
> 
> 
> My understanding is that your analysis is mostly based on running
> a profiler against the code. Network operations can be bottlenecked
> in other places.
> 
> You compare 'simple script using kombu' with 'script using 
> oslo.messaging'. You don't compare script using oslo.messaging
> before refactoring and 'after that. The latter would show whether
> refactoring was worth the effort. Your test shows that
> oslo.messaging performance sucks, but it's not definite that
> hotspots you've revealed, once fixed, will show huge boost.
> 
> My concern is that it may turn out that once all the effort to 
> refactor the code is done, we won't see major difference. So we
> need base numbers, and performance tests would be a great helper
> here.
> 
> 
> It's really sad for me to see so little faith in what I'm saying. 
> The test I've done using plain kombu driver was needed exactly to
> check that network is not the bottleneck for messaging
> performance. If you don't believe in my performance analysis we
> could ask someone else to do their own research and provide
> results.

Technology is not about faith. :)

First, let me make it clear I'm *not* against refactoring or anything
that will improve performance. I'm just a bit skeptical, but hopefully
you'll be able to show everyone I'm wrong, and then the change will
occur. :)

To add more velocity to your effort, strong arguments should be
present. To facilitate that, I would start from adding performance
tests that would give us some basis for discussion of changes proposed
later.

Then, describing proposed details in a spec will give more exposure to
your ideas. At the moment, I see general will to enhance the library,
but not enough details on how to achieve this. Specification can make
us think not about the burden of change that obviously makes people
skeptic about rewrite-all approach, but about specific technical issues.

> 
> Problem with refactoring that I'm planning is that it's not a
> minor refactoring that can be applied in one patch but it's the
> whole library rewritten from scratch.

You can still maintain a long sequence of patches, like we did when we
migrated neutron to oslo.messaging (it was like ~25 separate pieces).

> Existing messaging code was written long long time ago (in a galaxy
> far far away maybe?) and it was copy-pasted directly from nova. It
> was not built as a library and it was never intended to be used 
> outside of nova. Some parts of it cannot even work normally cause
> it was not designed to work with drivers like zeromq (matchmaker
> stuff).

oslo.messaging is NOT the code you can find in oslo-incubator rpc
module. It was hugely rewritten to expose a new, cleaner API. This is
btw one of the reasons migration to this new library is so painful. It
was painful to move to oslo.messaging, so we need clear need for a
change before switching to yet another library.

> 
> The reason I've raised this question on the mailing list was to get
> some agreement about future plans of oslo.messaging development and
> start working on it in coordination with community. For now I don't
> see any actions plan emerging from it. I would like to see us
> bringing more constructive ideas about what should be done.
> 
> If you think that first action should be profiling lets discuss how
> it should be implemented (cause it works for me just fine on my
> local PC). I guess we'll need to define some basic scenarios that
> would show us overall performance of the library.

Let's start from basic send/receive throughput, for tiny and large
messages, multiple consumers etc.

> There are a lot of questions that should be answered to implement
> this: Where such tests would run (jenking, local PC, devstack VM)?

I would expect it to be exposed to jenkins thru 'tox'. We then can set
up a separate job to run them and compare with a base line [TBD: what
*is* baseline?] to make sure we don't introduce performance regressions.

> How such scenarios should look like? How do we measure performance
> (cProfile, etc.)?

I think we're interested in message rate, not CPU utilization.

> How do we collect results? How do we analyze results to find
> bottlenecks? etc.
> 
> Another option would be to spend some of my free time implementing 
> mentioned refactoring (as I see it) and show you the results of 
> performance testing compared with existing code.

This approach generally doesn't work beyond PoC. Openstack is a
complex project, and we need to stick to procedures - spec review,
then coding, all in upstream, with no private branches outside common
infrastructure.

> The only problem with such approach is that my code won't be 
> oslo.messaging and it won't be accepted by community. It may be
> drop in base for v2.0 but I'm afraid this won't be acceptable
> either.
> 

Future does not occur here that way. If you want your work to be
consumed by community, you need to work with it.

> Regards, Alexei Kornienko
> 
> 
> 2014-06-30 17:51 GMT+03:00 Gordon Sim <gsim at redhat.com 
> <mailto:gsim at redhat.com>>:
> 
> On 06/30/2014 12:22 PM, Ihar Hrachyshka wrote:
> 
> Alexei Kornienko wrote:
> 
> Some performance tests may be introduced but they would be more 
> like functional tests since they require setup of actual messaging
> server (rabbit, etc.).
> 
> 
> Yes. I think we already have some. F.e. 
> tests/drivers/test_impl_qpid.__py attempts to use local Qpid
> server (backing up to fake server if it's not available).
> 
> 
> I always get failures when there is a real qpidd service listening 
> on the expected port. Does anyone else see this?
> 
> 
> 
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