On Oct 3, 2014, at 2:44 PM, Monty Taylor <mord...@inaugust.com> wrote:

> On 09/30/2014 12:07 PM, Tim Bell wrote:
>>> -----Original Message-----
>>> From: John Garbutt [mailto:j...@johngarbutt.com]
>>> Sent: 30 September 2014 15:35
>>> To: OpenStack Development Mailing List (not for usage questions)
>>> Subject: Re: [openstack-dev] [all] [tc] Multi-clouds integration by 
>>> OpenStack
>>> cascading
>>> On 30 September 2014 14:04, joehuang <joehu...@huawei.com> wrote:
>>>> Hello, Dear TC and all,
>>>> Large cloud operators prefer to deploy multiple OpenStack instances(as
>>> different zones), rather than a single monolithic OpenStack instance 
>>> because of
>>> these reasons:
>>>> 1) Multiple data centers distributed geographically;
>>>> 2) Multi-vendor business policy;
>>>> 3) Server nodes scale up modularized from 00's up to million;
>>>> 4) Fault and maintenance isolation between zones (only REST
>>>> interface);
>>>> At the same time, they also want to integrate these OpenStack instances 
>>>> into
>>> one cloud. Instead of proprietary orchestration layer, they want to use 
>>> standard
>>> OpenStack framework for Northbound API compatibility with HEAT/Horizon or
>>> other 3rd ecosystem apps.
>>>> We call this pattern as "OpenStack Cascading", with proposal described by
>>> [1][2]. PoC live demo video can be found[3][4].
>>>> Nova, Cinder, Neutron, Ceilometer and Glance (optional) are involved in the
>>> OpenStack cascading.
>>>> Kindly ask for cross program design summit session to discuss OpenStack
>>> cascading and the contribution to Kilo.
>>>> Kindly invite those who are interested in the OpenStack cascading to work
>>> together and contribute it to OpenStack.
>>>> (I applied for “other projects” track [5], but it would be better to
>>>> have a discussion as a formal cross program session, because many core
>>>> programs are involved )
>>>> [1] wiki: https://wiki.openstack.org/wiki/OpenStack_cascading_solution
>>>> [2] PoC source code: https://github.com/stackforge/tricircle
>>>> [3] Live demo video at YouTube:
>>>> https://www.youtube.com/watch?v=OSU6PYRz5qY
>>>> [4] Live demo video at Youku (low quality, for those who can't access
>>>> YouTube):http://v.youku.com/v_show/id_XNzkzNDQ3MDg4.html
>>>> [5]
>>>> http://www.mail-archive.com/openstack-dev@lists.openstack.org/msg36395
>>>> .html
>>> There are etherpads for suggesting cross project sessions here:
>>> https://wiki.openstack.org/wiki/Summit/Planning
>>> https://etherpad.openstack.org/p/kilo-crossproject-summit-topics
>>> I am interested at comparing this to Nova's cells concept:
>>> http://docs.openstack.org/trunk/config-reference/content/section_compute-
>>> cells.html
>>> Cells basically scales out a single datacenter region by aggregating 
>>> multiple child
>>> Nova installations with an API cell.
>>> Each child cell can be tested in isolation, via its own API, before joining 
>>> it up to
>>> an API cell, that adds it into the region. Each cell logically has its own 
>>> database
>>> and message queue, which helps get more independent failure domains. You can
>>> use cell level scheduling to restrict people or types of instances to 
>>> particular
>>> subsets of the cloud, if required.
>>> It doesn't attempt to aggregate between regions, they are kept independent.
>>> Except, the usual assumption that you have a common identity between all
>>> regions.
>>> It also keeps a single Cinder, Glance, Neutron deployment per region.
>>> It would be great to get some help hardening, testing, and building out 
>>> more of
>>> the cells vision. I suspect we may form a new Nova subteam to trying and 
>>> drive
>>> this work forward in kilo, if we can build up enough people wanting to work 
>>> on
>>> improving cells.
>> At CERN, we've deployed cells at scale but are finding a number of 
>> architectural issues that need resolution in the short term to attain 
>> feature parity. A vision of "we all run cells but some of us have only one" 
>> is not there yet. Typical examples are flavors, security groups and server 
>> groups, all of which are not yet implemented to the necessary levels for 
>> cell parent/child.
>> We would be very keen on agreeing the strategy in Paris so that we can 
>> ensure the gap is closed, test it in the gate and that future features 
>> cannot 'wishlist' cell support.
> I agree with this. I know that there are folks who don't like cells -
> but I think that ship has sailed. It's there - which means we need to
> make it first class.

Just out of curiosity, would you prioritize cells over split out unified 
quotas, or a split out scheduler, or split out virt drivers, or a split out 
..., or upgrades that work reliably or db quota consistency ([2]) or the other 
X things that need to be done to keep the 'openstack' ship afloat (neutron 
integration/migrations... the list can go on and on)?

To me that's the part that has always bugged me about cells, it seems like we 
have bigger 'fish to fry' to get the whole system working in a good manner 
instead of adding yet another fish in to the already overwhelmed fishery (this 
is an analogy, not reality, ha). It somehow didn't/doesn't feel right that we 
have so many other pieces of the puzzle that need work just to operate at a 
small scale that we should add another component in that makes the system as a 
whole that much harder to get right (with lovely commits such as [1]). Aka, 
focus on a building a solid 'small house' first before trying to build a 
mansion if you will, because if you can't build a stable small house you'll 
likely build a mansion that will crumble in on itself...

It also doesn't help that cells are a nova-specific concept that it doesn't 
seem like other projects have adopted (for better or worse) although this 
cascading design can be an alternative that could span across projects (with 
its own set of consistency warts I'm sure).

[1] https://github.com/openstack/nova/blob/master/nova/compute/api.py#L1553 
(what u wanted quota consistency?)
[2] https://review.openstack.org/#/c/125181/ 

>> Resources can be made available if we can agree the direction but current 
>> reviews are not progressing (such as 
>> https://bugs.launchpad.net/nova/+bug/1211011)
>> Tim
>>> Thanks,
>>> John
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