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From Göktürk Gezer <gokturk.ge...@gmail.com>
Subject Re: Question about Replication of Config Partition and Schema Partition
Date Wed, 11 Jul 2012 09:51:29 GMT
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.

I'll then share my findings on this thread.
>>
>> 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.
> Does this make sense?
>
> --
> Best Regards,
> -- Alex
>
Regards,
G

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