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From Göktürk Gezer <gokturk.ge...@gmail.com>
Subject Re: Question about Replication of Config Partition and Schema Partition
Date Tue, 10 Jul 2012 15:07:19 GMT
On Tue, Jul 10, 2012 at 4:37 PM, Emmanuel Lécharny <elecharny@gmail.com>wrote:

> Le 7/10/12 12:54 PM, Göktürk Gezer a écrit :
>
>  Hi Everyone,
>>
>> I would like to know, it config and schema partitions of one server node
>> can be candidate for replication?
>>
> Yes.


>  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.
>>
> We should not affect random OID to components. An OID should identify a
> unique object, so if you have some instance of this object on many
> instances of the server, then they should always have the same OID.

We can go with has values of component names. That would do the trick !

>
>
>> This is something we've postponed to discuss later, 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?
>>
> Depends. Replication is supposed to be configurable. You can replicate
> only part of the data, it's up to the administrator to tell what should be
> replicated, or not.
>
Well i don't believe replicating runtime information and plain data with
the same process is a good idea anymore. Right now changes on configuration
partition is read until next restart, but after migrating to OSGI it will.
So syncing the replicas to have same runtime footprint must be handled via
seperate subsystem, otherwise we're in trouble. There can be some switch in
replication configuration to specify whether replica's runtime
configuration will be the same. Apart from configuration we also have the
schema's backing that configuration entries, because they are not spread in
many location, that won't be much of a problem.

How replication is working for schema data ATM ?

>
> In the standard scenario, the configuration and schema should be
> replicated, that's pretty mandatory.
>
Configuration and configuration related schema must be handled in some
other way, if don't then we can not manage lifecycle of server in OSGI. If
some ApacheDS instance can obtain the reference to replica instance than we
can manage it incrementally as the configuration or backed schema changes.
ComponentHub is pretty much supporting that. However we should have access
to DirectoryService reference of replica, I guess this is not the case
right now?

> Does it help ?

Yeah thanks, but need more :)

>
>
> --
> Regards,
> Cordialement,
> Emmanuel Lécharny
> www.iktek.com
>
>

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