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From "Marc Boorshtein" <>
Subject Re: [ApacheDS] Specifying application level subtrees?
Date Fri, 21 Sep 2007 20:21:44 GMT

> > Thats why many virtual
> > directories have dynamic group plugins to make dynamic groups work and
> > act like static groups.
> Yes this is one such approach but it scares me in terms of the size of
> entries that
> will be returned.  You're going to be caching a lot in memory.  Consider a
> dynamic
> group with 1M members.  You now have to stuff your entry to be returned with
> 1M
> values for the [unique]member attribute.  If the average size for a member's
> internationalized
> DN is 512 bytes then we're going to return an entry which is 512M+ in size.
> I don't want
> to keep this entry in memory as the server builds it to send it out the
> door.

If the application were pulling all members back then yes, this would
be a major issue.  It is not however a requirement to bring all the
members into the virtual directory and then return them to the client
to test a group membership.  Generally a group test will look like:

ldapsearch ... -b "cn=my group,ou=groups,dc=domain,dc=com" -s base
"(uniqueMember=cn=me,ou=people,dc=domain,dc=com") 1.1

If the user is a member of the group then the group dn will be
returned as the only entry.  While there are definitely really badly
written applications that will retrieve the entire group and then do
an evaluation thats pretty rare.  Even if it does happen you would
have the same problem with a static group.  I've actualy deployed this
solution with Oracle's virtual directory where the static members were
150k-500k members (and is a 256mb entry any better then a 512mb entry?
:-D) and it worked very well.

I'm still not sure what the advantage of your solution is over a
dynamic group, but I'm probably missing something.

> I'd love to do that but for the reasons above I'm constrained.  The search
> control based
> approach is perhaps the best way to do this but then again the client has to
> get a bit
> smarter.  Perhaps both options can exist and when the size of the group is
> beyond some
> threshold the static group like lookup fails?

well, applications just aren't written well.  1/2 the commercial LDAP
applications out there have poorly written LDAP modules that were
built for a specific customer and were just 'released'.

> This get's me to another point.  LDAP needs a partial result return protocol
> response
> which could allow streaming large amounts of attributes back to clients to
> prevent
> excessive memory consumption.
> > The answer to 'why dont we do it' is that applications need to be able
> > to consume it.
> Yep this is the biggest problem but applications need to change and so does
> otherwise we're stuck doing stupid things like HTTP did with statelessness
> for decades.

Good luck to you there...I don't know that there will ever be an
LDAPv4 but I suppose thats another discussion.

> Incidentally Authorization is already handled correctly by the X.500 model
> which is being
> specified in LDAP with the work being done by Steven Legg here:
> Authorization does not need this after this draft becomes an RFC which shows
> a strong
> liklihood.  ApacheDS uses this same model - this is why we stuck so close to
> the X.500
> standards in our AC implementation.

Well, I'm not a huge X.500 fan but you say tomatoe....I'm curios to
check out the spec though.  Thanks for the pointer.

> Getting back to groups.  This proposed mechanism for dynamic groups has it's
> basis in X.500.
> The excellent points regarding client consumption that you sited can be
> ameliorated using some
> existing protocol features such as extended operations and search controls
> but we must explore
> the impact of them on clients and on the server.  I smell a potential draft
> for a new specification
> here.  Interested?

Always glad to be involved and bounce ideas around.  I think I take a
different tact but thats probably OK too.

Extended operations & controls are great and all but applications just
don't use them.  If I were to design my super group it would have 4

1.  Members can be dynamic
2.  Members can be static
3.  Members can be other groups
4.  I can test a group membership with a single ldap search call

Now how to do this under the covers I bet you are far better at
answering then me.  Again I can do this with a virtual directory now
(MyVirtualDirectory has a DynamicGroups insert and a EmbeddedGroups
insert that does this).  Maybe ApaceDS can do it better because it has
all of its data locally (actually I'm positive it could).

I do say I'd be very interested to get the other open source ldap
proejects (opends, openldap, penrose & fedorads) opinions on the


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