Open Stack

So this brings up an interesting issue, the reason ZK exists or partially exists is that something like ZK api's over DB weren't really possible. Or that’s what I thought :-P

Or they weren't possible in a accurate and provable accurate manner. So spending time creating apis that 'sorta' work with DB's but really don't (since ZK wouldn't exist if it was possible) does seem sorta awkward. I thought most cloud providers are already using zookeeper, for these exact same reasons, and deploying it now-adays is pretty simple…

I just worry about providing API's that really don't work correctly with DB's that will cause more bugs (since certain problems just can't be done with a DB, or at least any of the DBs that I have used, maybe db2 can, idk) that we will have to say 'oh ya we know that doesn't work with a DB'. But maybe that is a compromise that we have to make and is a evolutionary process where the amount of bugs that will be caused by DB impls will eventually just cause people to move to the more attractive ZK backend… Its also sorta concerning that those types of DB like bugs will be harder than heck to trace down, but that might be a different issue that we can resolve.

From: Alex Glikson <GLIKSON at il.ibm.com<mailto:GLIKSON at il.ibm.com>>
Reply-To: OpenStack Development Mailing List <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Date: Thursday, May 2, 2013 7:53 AM
To: OpenStack Development Mailing List <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Subject: Re: [openstack-dev] Nova workflow management update

Changbin Liu <changbin.liu at gmail.com<mailto:changbin.liu at gmail.com>> wrote on 02/05/2013 05:32:05 PM:

> Subject: Re: [openstack-dev] Nova workflow management update
>
> Hi Joshua,
>
> Just to share some thoughts:
[...]

Using ZK makes a lot of sense.. The problem is that making ZooKeeper a mandatory component to support even basic workflow management might be an issue. So, the approach which seems to make most sense is to define abstract internal interfaces for the various capabilities that ZK can provide (distributed locking, leader election, etc), and then have one or more implementations (one of which might be based on ZK). This is the approach that has been taken for the membership service (service group monitoring APIs) -- introducing the flexibility to use ZK backend, but keeping the default to be DB-backed.

Regards,
Alex

P.S. thinking about this.. would it be possible to implement ZK APIs over a DB? with some limitations, perhaps..
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