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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