On 7/15/10 9:03 PM, Kiran Ayyagari wrote:
have not touched this part of the server so here are some (naive) questions
On Thu, Jul 15, 2010 at 11:03 PM, Emmanuel Lecharny<[email protected]> wrote:
Hi guys,
we have serious issues with the way we manage subentries in the server. Not
that it's not working, but it's certainly not good enough for anything but a
toy server.
Let me first give some heads up about what's going on.
A subentry is associated with an AdministrativePoint (AP), and defines a
selection of entries which will be affected depending on the AP role. Those
roles are :
- Access Control
- Collective Attributes
- SubSchema (not active atm)
- Triggers (ADS specific).
For instance, if we have a tree with a set of entries associated with a
location (ie, c=France), we may define a subentry with a Collective
Attribute role telling the server that every entry under the c=France branch
will have a specific attribute added. We don't have then to add this
attribute to *every* entry in this branch...
Anyway...
A subentry defines a selection using a filter, and a base DN for this filter
to be active from.
Right now, a Subentry is attached to an AP as a (quite) normal entry, and
when we add this subentry, we modidy *all* the selected entries (using the
subentry filter and the base DN) will be modified to have a new attribute
added.
AFAIU we update all the entries with this new info, do we really need
to do this?
Of course not.
is it done that way to avoid any search evaluation costs?
No, I think it's was done this way because it was the easiest way to
make it works, as a preliminary approach. Sometime, you have to balance
between good and best.
This added attribute contains a DN poiting to the associated
subentry, so that when we process this entry, we can immediately know that
it's associated with an AP.
So far, so good : processing an entry is fast, as we have all what we need
when we have the entry. But the dark side is that if we have millions of
entries, when we add an AP and a subentry, we may have to modify potentially
*millions* of entries to add this attribute. Not good...
How can we improve this process ?
The idea would be to search for the APs when we process an entry, but it has
to be fast. How can we do that ? Simple : we use the entry's DN and using a
DN cache, we can get all the APs associated with an entry knowing its DN.
It's as costly as the depth of the entry's DN. Once we have grabbed the APs,
we will have to evaluate the entry to know if it's part of the selections
defined by the APs' subentry. Done.
Is it costly ? Only marginaly compared to the current algorithm, as we have
to lookup for the AP, when we have this list in an Attribute in the current
server. But we spare the big modifications when adding - or
removing/renaming/moving - a subentry.
What we just need is a APs cache and a way to process it.
This is what I will work on in the next few days if nobody objects or find a
better algorithm.
how about having a Index on subEntry instead of a cache, one immediate
advantage I see is
that we don't need to cache DNs which will help in minimizing the
modify() operation's time.
We just cache the APs' DN, and we won't have many. We will also have an
index on subentry, but this is different.
When we init the system, we will load all the subentries in the cache,
using the index to get them from the backend.--
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com
