On Wed, 07 Jan 2015 15:25:30 -0500
Dmitri Pal <dpal(a)redhat.com> wrote:
On 01/07/2015 03:05 PM, Simo Sorce wrote:
> On Tue, 06 Jan 2015 09:59:08 -0500
> Dmitri Pal <dpal(a)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:
>>>>>> 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
>>> (Yes, this is the reason I chose the asterisk notation in the
>>> first place) _______________________________________________
>>> sssd-devel mailing list
>> 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
>> - I do not think we should rely on enumeration. I think we should
>> do a lookup since these operations will be rare.
> 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
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.
IMO there should be a way for those queries to actually go online. We
can, however, not process all results. We can explicitly say "first
10 or 20 results and that is it". It can be an argument of the call
with the default being a value in sssd.conf.
It may make sense to think of a "ranged" interface for wildcard
lookups, where you have to explicitly provide the range you want capped
to a max length defined in sssd conf, and if you exceed that size you
get an error.
This way users are forced to think about how many result they want/can
So the wildcard interface will be different from exact match interface.
Simo Sorce * Red Hat, Inc * New York