On Thu, Jan 08, 2015 at 09:16:53PM +0100, Pavel Březina wrote:
> On 01/08/2015 07:44 PM, Jakub Hrozek wrote:
>> On Thu, Jan 08, 2015 at 09:35:42AM -0500, Dmitri Pal wrote:
>>> 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 <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:
>>>>>>>>>>>> *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)
_______________________________________________
>>>>>>>>> sssd-devel mailing list
>>>>>>>>> sssd-devel(a)lists.fedorahosted.org
>>>>>>>>>
https://lists.fedorahosted.org/mailman/listinfo/sssd-devel
>>>>>>>> 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.
>>
>> OK, I filed
https://fedorahosted.org/sssd/ticket/2553 into the same
>> milestone.
>
> This brings another question. Because we are talking about
> ListUsersByFilter() that returns a list of object paths the only thing that
> is needed to construct such path is UID. So we can avoid membership
> evaluation here which would reduce load and processing time.
>
> The caller will be probably interested mostly in user name, is that correct?
> So we can skip membership evaluation at all unless group property is
> requested.
Yes, we know updating membership is a costly operation, that's why there is a
separate method for that.
Ok. I will prepare a design page that will cover all this.