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From Alex Karasulu <akaras...@apache.org>
Subject Re: Question about Replication of Config Partition and Schema Partition
Date Wed, 11 Jul 2012 15:02:05 GMT
On Wed, Jul 11, 2012 at 12:51 PM, Göktürk Gezer <gokturk.gezer@gmail.com>wrote:

>
> On Jul 11, 2012 12:13 AM, "Alex Karasulu" <akarasulu@apache.org> wrote:
> >
> >
> >
> > On Tue, Jul 10, 2012 at 1:54 PM, Göktürk Gezer <gokturk.gezer@gmail.com>
> wrote:
> >>
> >> Hi Everyone,
> >>
> >> I would like to know, it config and schema partitions of one server
> node can be candidate for replication? If replication of some ApacheDS
> instance will also clone its config and schema partition, we have a little
> problem because of the randomly assigned OIDs to component factories. So
> lets say ApacheDS1 and ApacheDS2 both have same set of interceptors,
> because of the nature of OSGI those can be introduced in different order in
> two different server node which results in schema partitions having
> different OID assignments for same components across 2 server node.
> >>
> >
> > Right now I would not worry about replication. You can solve this
> problem later. Just focus on your part functioning properly. This will be a
> problem we will need to solve anyway. Plus replication is not really there
> in a dependable way.
> >
> This kind of things caused me to reimplement osgi layer several times. I
> have some strange feelings, this will be one of them. Because of the things
> we discussed with emanuel, it may not be just easy later. Just to be sure
> that I won't rewrite completely again in the close future, I'll review some
> replication scenarios, and study some mechanisms which people use to
> implement replication these days like Apache ZooKeeper and Cellar.


That's wise. Also to design for flexibility just in case.


> I'll then share my findings on this thread.
>
>
Thanks.


> >>
> >> This is something we've postponed to discuss later,
> >
> >
> > Exactly what I started writing above.
> >
> >>
> >> it's not a concern for single server but in replication scenario i'd
> like to know how this effects consistency between distinct server nodes.
> I'm not so sure what is being replicated in our implementation, some
> partition or entire server with all of its runtime components and
> configuration?
> >>
> >
> > Eventually the replication mechanism will need to support partial and
> fractional replication. It's way over simplified and does not have the
> control structures for us to properly configure it in a fine grained
> manner.
> >
> ZooKeeper based replication can help us out here with some new replication
> mechanism with lots of control. I'll give it a look.
>
> > This will need to change of course but I'd really like to review
> replication after we finish with the Txn stuff because then it will make
> internal replication handling much clearer for us then.
> >
> Sure, it is primary. What I am trying is to get some early picture of
> replication system's effect on configuration partition. So that I can make
> sure this and osgi does not clash. These concerns may not be look so
> important, but they are. they are some nasty side effects of keeping
> configuration also in partition rather then externally managed store.
>
>
Cool, what you say is very reasonable. My personal approach is to make it
really flexible in case stuff like this does pop up later. The game never
ends, it's all about being able to react to new complications without
having to change everything you wrote.


> > Does this make sense?
> >
> > --
> > Best Regards,
> > -- Alex
> >
> Regards,
> G
>
>


-- 
Best Regards,
-- Alex

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