In the spirt of openness, yes I do think they are all needed.

If they are not supported, then openstack is not open, it is a closed
system.

We should strive to innovate, not strive to be stuck with the status quo.

To me it is a developers decision to pick the right solution, if that
solution involves some complexity then u make it a pluggable solution.
Your view of the right solution will likely not be the view of someone
elses right solution in the end anyway (and u likely can't predict future
solutions that will be applicable anyway). If u just say no to that plugin
then u are just excluding people from participating in your project and
this is imho against the spirt of openness in general. And those people
who would have contributed will just start looking elsewhere for a
solution which does work. This kills the openstack...

On 10/31/13 10:17 AM, "Monty Taylor" <mord...@inaugust.com> wrote:

>Sigh.
>
>Yay!!!! We've added more competing methods of complexity!!!
>
>Seriously. We now think that rabbit and zookeeper and mysql are ALL
>needed?
>
>Joshua Harlow <harlo...@yahoo-inc.com> wrote:
>
>>I'm pretty sure the cats out of the bag.
>>
>>https://github.com/openstack/requirements/blob/master/global-requirements
>>.t
>>xt#L29
>>
>>https://kazoo.readthedocs.org/en/latest/
>>
>>-Josh
>>
>>On 10/31/13 7:43 AM, "Monty Taylor" <mord...@inaugust.com> wrote:
>>
>>>
>>>
>>>On 10/30/2013 10:42 AM, Clint Byrum wrote:
>>>> So, recently we've had quite a long thread in gerrit regarding locking
>>>> in Heat:
>>>> 
>>>> https://review.openstack.org/#/c/49440/
>>>> 
>>>> In the patch, there are two distributed lock drivers. One uses SQL,
>>>> and suffers from all the problems you might imagine a SQL based
>>>>locking
>>>> system would. It is extremely hard to detect dead lock holders, so we
>>>> end up with really long timeouts. The other is ZooKeeper.
>>>> 
>>>> I'm on record as saying we're not using ZooKeeper. It is a little
>>>> embarrassing to have taken such a position without really thinking
>>>>things
>>>> through. The main reason I feel this way though, is not because
>>>>ZooKeeper
>>>> wouldn't work for locking, but because I think locking is a mistake.
>>>> 
>>>> The current multi-engine paradigm has a race condition. If you have a
>>>> stack action going on, the state is held in the engine itself, and not
>>>> in the database, so if another engine starts working on another
>>>>action,
>>>> they will conflict.
>>>> 
>>>> The locking paradigm is meant to prevent this. But I think this is a
>>>> huge mistake.
>>>> 
>>>> The engine should store _all_ of its state in a distributed data store
>>>> of some kind. Any engine should be aware of what is already happening
>>>> with the stack from this state and act accordingly. That includes the
>>>> engine currently working on actions. When viewed through this lense,
>>>> to me, locking is a poor excuse for serializing the state of the
>>>>engine
>>>> scheduler.
>>>> 
>>>> It feels like TaskFlow is the answer, with an eye for making sure
>>>> TaskFlow can be made to work with distributed state. I am not well
>>>> versed on TaskFlow's details though, so I may be wrong. It worries me
>>>> that TaskFlow has existed a while and doesn't seem to be solving real
>>>> problems, but maybe I'm wrong and it is actually in use already.
>>>> 
>>>> Anyway, as a band-aid, we may _have_ to do locking. For that,
>>>>ZooKeeper
>>>> has some real advantages over using the database. But there is
>>>>hesitance
>>>> because it is not widely supported in OpenStack. What say you,
>>>>OpenStack
>>>> community? Should we keep ZooKeeper out of our.. zoo?
>>>
>>>Yes. I'm strongly opposed to ZooKeeper finding its way into the already
>>>complex pile of things we use.
>>>
>>>_______________________________________________
>>>OpenStack-dev mailing list
>>>OpenStack-dev@lists.openstack.org
>>>http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>
>>


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