Rui, you still can run multiple nova-scheduler process now.

2015-03-05 10:55 GMT+08:00 Rui Chen <chenrui.m...@gmail.com>:

> Looks like it's a complicated problem, and nova-scheduler can't scale-out
> horizontally in active/active mode.
>
> Maybe we should illustrate the problem in the HA docs.
>
> http://docs.openstack.org/high-availability-guide/content/_schedulers.html
>
> Thanks for everybody's attention.
>
> 2015-03-05 5:38 GMT+08:00 Mike Bayer <mba...@redhat.com>:
>
>>
>>
>> Attila Fazekas <afaze...@redhat.com> wrote:
>>
>> > Hi,
>> >
>> > I wonder what is the planned future of the scheduling.
>> >
>> > The scheduler does a lot of high field number query,
>> > which is CPU expensive when you are using sqlalchemy-orm.
>> > Does anyone tried to switch those operations to sqlalchemy-core ?
>>
>> An upcoming feature in SQLAlchemy 1.0 will remove the vast majority of CPU
>> overhead from the query side of SQLAlchemy ORM by caching all the work
>> done
>> up until the SQL is emitted, including all the function overhead of
>> building
>> up the Query object, producing a core select() object internally from the
>> Query, working out a large part of the object fetch strategies, and
>> finally
>> the string compilation of the select() into a string as well as organizing
>> the typing information for result columns. With a query that is
>> constructed
>> using the “Baked” feature, all of these steps are cached in memory and
>> held
>> persistently; the same query can then be re-used at which point all of
>> these
>> steps are skipped. The system produces the cache key based on the in-place
>> construction of the Query using lambdas so no major changes to code
>> structure are needed; just the way the Query modifications are performed
>> needs to be preceded with “lambda q:”, essentially.
>>
>> With this approach, the traditional session.query(Model) approach can go
>> from start to SQL being emitted with an order of magnitude less function
>> calls. On the fetch side, fetching individual columns instead of full
>> entities has always been an option with ORM and is about the same speed
>> as a
>> Core fetch of rows. So using ORM with minimal changes to existing ORM code
>> you can get performance even better than you’d get using Core directly,
>> since caching of the string compilation is also added.
>>
>> On the persist side, the new bulk insert / update features provide a
>> bridge
>> from ORM-mapped objects to bulk inserts/updates without any unit of work
>> sorting going on. ORM mapped objects are still more expensive to use in
>> that
>> instantiation and state change is still more expensive, but bulk
>> insert/update accepts dictionaries as well, which again is competitive
>> with
>> a straight Core insert.
>>
>> Both of these features are completed in the master branch, the “baked
>> query”
>> feature just needs documentation, and I’m basically two or three tickets
>> away from beta releases of 1.0. The “Baked” feature itself lives as an
>> extension and if we really wanted, I could backport it into oslo.db as
>> well
>> so that it works against 0.9.
>>
>> So I’d ask that folks please hold off on any kind of migration from ORM to
>> Core for performance reasons. I’ve spent the past several months adding
>> features directly to SQLAlchemy that allow an ORM-based app to have routes
>> to operations that perform just as fast as that of Core without a rewrite
>> of
>> code.
>>
>> > The scheduler does lot of thing in the application, like filtering
>> > what can be done on the DB level more efficiently. Why it is not done
>> > on the DB side ?
>> >
>> > There are use cases when the scheduler would need to know even more
>> data,
>> > Is there a plan for keeping `everything` in all schedulers process
>> memory up-to-date ?
>> > (Maybe zookeeper)
>> >
>> > The opposite way would be to move most operation into the DB side,
>> > since the DB already knows everything.
>> > (stored procedures ?)
>> >
>> > Best Regards,
>> > Attila
>> >
>> >
>> > ----- Original Message -----
>> >> From: "Rui Chen" <chenrui.m...@gmail.com>
>> >> To: "OpenStack Development Mailing List (not for usage questions)" <
>> openstack-dev@lists.openstack.org>
>> >> Sent: Wednesday, March 4, 2015 4:51:07 AM
>> >> Subject: [openstack-dev] [nova] blueprint about multiple workers
>> supported   in nova-scheduler
>> >>
>> >> Hi all,
>> >>
>> >> I want to make it easy to launch a bunch of scheduler processes on a
>> host,
>> >> multiple scheduler workers will make use of multiple processors of
>> host and
>> >> enhance the performance of nova-scheduler.
>> >>
>> >> I had registered a blueprint and commit a patch to implement it.
>> >>
>> https://blueprints.launchpad.net/nova/+spec/scheduler-multiple-workers-support
>> >>
>> >> This patch had applied in our performance environment and pass some
>> test
>> >> cases, like: concurrent booting multiple instances, currently we
>> didn't find
>> >> inconsistent issue.
>> >>
>> >> IMO, nova-scheduler should been scaled horizontally on easily way, the
>> >> multiple workers should been supported as an out of box feature.
>> >>
>> >> Please feel free to discuss this feature, thanks.
>> >>
>> >> Best Regards
>> >>
>> >>
>> >>
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