[openstack-dev] [Heat] Locking and ZooKeeper - a space oddysey

Joshua Harlow harlowja at yahoo-inc.com
Wed Oct 30 19:45:20 UTC 2013


+1 ;)

On 10/30/13 12:37 PM, "Clint Byrum" <clint at fewbar.com> wrote:

>Excerpts from Joshua Harlow's message of 2013-10-30 11:57:30 -0700:
>> As for the mutex and locking and all that problem.
>> 
>> I would expect locking to be a necessity at some point for openstack.
>> 
>> Even if the state transitions are the locks themselves (that¹s still a
>> lock by another name imho) and u need a reliable way to store and change
>> those state transitions (aka what the last one was, what the next one
>>is).
>> A database can be likely ok here but is not ideal as complexity
>>increases.
>> The other part that I think zookeepr addresses is similar to how it is
>> used in nova, where its used as a 'liveness' system, where instead of
>> consistently updating a database with heartbeats zookeeper itself
>> maintains that information without requiring constant updates to a DB
>> (which doesn't scale).
>
>I'm not so concerned with locks under the covers, I am concerned with
>locking as a paradigm. It is too low level for what Heat is aiming at.
>Yes of course serialization can and often does rely on locking. My point
>is really that we should not care how serialization happens, we should
>just express the work-flow, and let the underlying mechanisms distribute
>and manage it as it is completed. My sincerest hope is that we can make
>TaskFlow do this.
>
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