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Hi,

Please find some answers inline.

Regards,
Alexei

On 06/10/2014 03:06 PM, Flavio Percoco wrote:
> On 10/06/14 15:03 +0400, Dina Belova wrote:
>> Hello, stackers!
>>
>>
>> Oslo.messaging is future of how different OpenStack components 
>> communicate with
>> each other, and really I'd love to start discussion about how we can 
>> make this
>> library even better then it's now and how can we refactor it make more
>> production-ready.
>>
>>
>> As we all remember, oslo.messaging was initially inspired to be 
>> created as a
>> logical continuation of nova.rpc - as a separated library, with lots of
>> transports supported, etc. That's why oslo.messaging inherited not only
>> advantages of now did the nova.rpc work (and it were lots of them), 
>> but also
>> some architectural decisions that currently sometimes lead to the 
>> performance
>> issues (we met some of them while Ceilometer performance testing [1] 
>> during the
>> Icehouse).
>>
>>
>> For instance, simple testing messaging server (with connection pool and
>> eventlet) can process 700 messages per second. The same functionality
>> implemented using plain kombu (without connection pool and eventlet)  
>> driver is
>> processing ten times more - 7000-8000 messages per second.
>>
>>
>> So we have the following suggestions about how we may make this 
>> process better
>> and quicker (and really I'd love to collect your feedback, folks):
>>
>>
>> 1) Currently we have main loop running in the Executor class, and I 
>> guess it'll
>> be much better to move it to the Server class, as it'll make 
>> relationship
>> between the classes easier and will leave Executor only one task - 
>> process the
>> message and that's it (in blocking or eventlet mode). Moreover, this 
>> will make
>> further refactoring much easier.
>
> To some extent, the executors are part of the server class since the
> later is the one actually controlling them. If I understood your
> proposal, the server class would implement the event loop, which means
> we would have an EventletServer / BlockingServer, right?
>
> If what I said is what you meant, then I disagree. Executors keep the
> eventloop isolated from other parts of the library and this is really
> important for us. One of the reason is to easily support multiple
> python versions - by having different event loops.
>
> Is my assumption correct? Could you elaborate more?
No It's not how we plan it. Server will do the loop and pass received 
message to dispatcher and executor. It means that we would still have 
blocking executor and eventlet executor in the same server class. We 
would just change the implementation part to make it more consistent and 
easier to control.

>
>>
>> 2) Some of the drivers implementations (such as impl_rabbit and 
>> impl_qpid, for
>> instance) are full of useless separated classes that in reality might be
>> included to other ones. There are already some changes making the whole
>> structure easier [2], and after the 1st issue will be solved 
>> Dispatcher and
>> Listener also will be able to be refactored.
>
> This was done on purpose. The idea was to focus on backwards
> compatibility rather than cleaning up/improving the drivers. That
> said, sounds like those drivers could user some clean up. However, I
> think we should first extend the test suite a bit more before hacking
> the existing drivers.
>
>
>>
>> 3) If we'll separate RPC functionality and messaging functionality 
>> it'll make
>> code base clean and easily reused.
>
> What do you mean with this?
We mean that current drivers are written with RPC code hardcoded inside 
(ReplyWaiter, etc.). Thats not how messaging library is supposed to 
work. We can move RPC to a separate layer and this would be beneficial 
for both rpc (code will become more clean and less error-prone) and core 
messaging part (we'll be able to implement messaging in way that will 
work much faster).
>
>>
>> 4) Connection pool can be refactored to implement more efficient 
>> connection
>> reusage.
>
> Please, elaborate. What changes do you envision?
Currently there is a class that is called ConnectionContext that is used 
to manage pool. Additionaly it can be accessed/configured in several 
other places. If we refactor it a little bit it would be much easier to 
use connections from the pool.
>
> As Dims suggested, I think filing some specs for this (and keeping the
> proposals separate) would help a lot in understanding what the exact
> plan is.
>
> Glad to know you're looking forward to help improving oslo.messaging.
>
> Thanks,
> Flavio
>
>> Folks, are you ok with such a plan? Alexey Kornienko already started 
>> some of
>> this work [2], but really we want to be sure that we chose the 
>> correct vector
>> of development here.
>>
>>
>> Thanks!
>>
>>
>> [1] https://docs.google.com/document/d/
>> 1ARpKiYW2WN94JloG0prNcLjMeom-ySVhe8fvjXG_uRU/edit?usp=sharing
>>
>> [2] https://review.openstack.org/#/q/
>> status:open+owner:akornienko+project:openstack/oslo.messaging,n,z
>>
>>
>> Best regards,
>>
>> Dina Belova
>>
>> Software Engineer
>>
>> Mirantis Inc.
>>
>
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>
>
>
>
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