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From "Alex Karasulu" <akaras...@apache.org>
Subject Re: [ApacheDS] Mitosis status inquiry
Date Tue, 25 Sep 2007 18:45:52 GMT
Hey Martin sorry for taking so long to respond to you especially when
you responded so quickly and thoroughly.  More in line ...

On 9/21/07, Martin Alderson <equim@planetquake.com> wrote:
>
> Hi Alex,
>
> For my fairly limited use mitosis is performing very well.


This is excellent news.

I've slacked off a bit over the last few weeks but will try to get back
> onto it soon.


No worries me too.  I keep context switching these days myself.

For stable use there is still that critical issue where a change on the
> same entry on multiple servers will lead to a permanently inconsistent
> state.  I'll make that my priority soon.


Ok what I want to do is setup and environment soon and start trying to
reproduce this as well as any other problems.  This way I can work with
you or at least help answer any questions you have while attacking this
problem.  I guess we can have intermediate states where the replicas
are not in sync but they must converge over time so this is a critical
issue.
I'll try to help out as best as I can on this.

I also recently came across a minor timeout issue which I think is a
> problem in MINA.  I'll investigate that more soon too.


This is new to me but if you localize it I'm sure we can fix it.

Aside from that there are niggling issues like replication of schema
> changes.


Yes this is something I am dreading. It's almost as if replicating a
partition must force replicating the schema across that cluster but
other clusters on different partitions will be all tied together for schema
changes.

This is why Microsoft decided to put schema into each partition for ADAM.
Although painful we could do the same but I think we can work around this
without
one offs but it will shift the design a bit.

Once these issues have been worked out I think we have a
> stable replication system.


Yep.

There are some features that I guess we really need to get in for it to
> actually be useful for the majority of users though.  The main things
> that come to mind are selective replication, encryption, schedules and
> removing the dependency on Derby.


Yes these are also my concerns especially encrypting the replication
channel.
We have some ideas that Ersin and I tossed around regarding all these
issues.

I guess we should start simple.  First we should think about integrating the

UUID capabilities which are part of mitosis into ApacheDS core so UUID is
supported whether you turn on replication or not.

Then from there I'd like to make the quartz scheduler a core service (not
interceptor) that is accessible from the DirectoryService interface to be
able to
schedule anything.

So moving these things up simplifies Mitosis a bit.

Then it's reasonable to just move the replication log off of Derby into a
custom
store implementation based on JDBM.  Eventually we'll need to expose this
data
via LDAP but we don't need to do it immediately.  For now getting rid of the
dep
and having a clean store implementation is enough.

I know you and Ersin are thinking about possible design changes although
> to me those can be done incrementally later on as required.  I doubt
> that I will be a driving force behind these changes but am willing to
> help.
>

Right I agree with you on the incremental changes.  Don't sell yourself
short the
new design changes are things I think you can easily grok.  Plus we're not
moving
fast with anything at the moment - we just have ideas.  The problem has been

where to dig in and start getting traction.  I think we can do the things
above in
parallel with introducing design changes as well.

Alex

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