On 01/08/2015 04:05 AM, Jakub Hrozek wrote:
On Wed, Jan 07, 2015 at 03:41:01PM -0500, Simo Sorce wrote:
On Wed, 07 Jan 2015 15:25:30 -0500
Dmitri Pal <d...@redhat.com> wrote:

On 01/07/2015 03:05 PM, Simo Sorce wrote:
On Tue, 06 Jan 2015 09:59:08 -0500
Dmitri Pal <d...@redhat.com> wrote:

On 01/06/2015 05:54 AM, Jakub Hrozek wrote:
On Tue, Jan 06, 2015 at 11:31:55AM +0100, Pavel Březina wrote:
*Users*
Do we want also to have methods ListDomainUsers() and
ListUsers() without the name filter?
To list all? What about using '*' for that?
We can implement it this way internally, but exposing an easier
way to the consumers is nice, imho.
I'm not too opposed, although I prefer minimal APIs.

However, do we actually want to allow to list all users? As
Dmitri suggested we may want to require the minimum filter
length since the number of users may be very high. The maximum
D-Bus message is 128MiB so I think we are good there but I think
it can be very time consuming to return all users without some
sort of paging.
This feature is internally dependant on enumerate=true, where we
already store all standard POSIX attributes (struct passwd, struct
group) in-memory, do you think the D-Bus "enumeration" provides
that much overhead?

Paging would be really complex, we'd need to store the full
results in-memory per-client anyway and then pass around some
kind of cookie to resume iteration..

In a centralized environment, I wouldn't expect the listing
commands to be used that commonly. Greeters or login managers
(gdm) would typically use the cached users instead. Some
applications (Hi, RHEV-M!) choose to display all their users in
some kind of table and then I would expect them to implement
paging themselves:

for letter in a..z:
       users = ListUsersByNameFilter($letter)

Do we want some other filter options as well?
In the design I wanted to keep the filtering simple. Unless we
receive some other requirements..
Yes, you suggested to allow only asterisk. Implement full regular
expression efficiently as Dmitri would be quite problematic since
ldb doesn't support regex lookup thus we would have to do this
ourselves and therefore we would loose indices, or am I wrong?
I guess we'd have to grab all the entries and filter them
ourselves..

(Yes, this is the reason I chose the asterisk notation in the
first place) _______________________________________________
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Several points:

- IMO having a full regular expression support will be an overhead.
- "Begins with" filtering with * to indicate the remaining part is
good enough
reasonable

- I do not think we should rely on enumeration. I think we should
do a lookup since these operations will be rare.
Nope.
This is the same thinking the implementers of the nss interface went
through. And then users started using enumeration all the time.

It may be ok to let users programmatically force full enumeration
somehow. But the default should be to return only what is in cache.
If you do otherwise people will test applications using * with 3
users on the system and then fail spectacularly when there are
actually 100K users in the directory.
I think there is a problem with the approach you suggest.

Say there is an application that allows you to list groups starting
with a letter. It is used to define roles for application
administration.

Assume that there is a group "Agroup". It is a new group that does
not have users yet. But it was created for use with the application
so that roles can be associated with this group. The admin of the
application thus wants to start using it.
This group will never be looked up if "A*" query will be run against
cache because it will not end up in cache. That would force admin to
turn full enumeration on SSSD. This is bad.
What matters is the '*' does not do enumeration, if 'ABC*' causes an
online lookup it is fine imo.
Yes, this is exactly what I was proposing. However, handling 'ABC*' on
the back end side must be implemented, currently we only handle a single
entry or enumeration.

I might have confused you because I proposed to first finish the DBus
*responder* work and temporarily require enumeration until we extend the
back end.

I hope it makes sense now.

As long as the work is bound to the same milestone the order does not matter.

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--
Thank you,
Dmitri Pal

Sr. Engineering Manager IdM portfolio
Red Hat, Inc.

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