On Thu, Aug 04, 2016 at 11:26:41AM +0200, Jakub Hrozek wrote: > On Thu, Aug 04, 2016 at 11:19:36AM +0200, Lukas Slebodnik wrote: > > On (04/08/16 11:15), Jakub Hrozek wrote: > > >On Thu, Aug 04, 2016 at 08:45:00AM +0200, Lukas Slebodnik wrote: > > >> On (03/08/16 18:56), Lukas Slebodnik wrote: > > >> >On (29/07/16 16:41), Jakub Hrozek wrote: > > >> >>On Thu, Jul 28, 2016 at 01:56:50PM +0200, Jakub Hrozek wrote: > > >> >>> On Thu, Jul 28, 2016 at 01:33:32PM +0200, Lukas Slebodnik wrote: > > >> >>> > On (28/07/16 12:06), thierry bordaz wrote: > > >> >>> > >On 07/28/2016 09:39 AM, Jakub Hrozek wrote: > > >> >>> > >> On Wed, Jul 27, 2016 at 04:09:07PM +0200, thierry bordaz wrote: > > >> >>> > >> > > > >> >>> > >> > On 07/27/2016 03:36 PM, Jakub Hrozek wrote: > > >> >>> > >> > > On Wed, Jul 27, 2016 at 02:55:37PM +0200, thierry bordaz > > >> >>> > >> > > wrote: > > >> >>> > >> > > > On 07/27/2016 01:56 PM, Jakub Hrozek wrote: > > >> >>> > >> > > > > On Wed, Jul 27, 2016 at 01:03:59PM +0200, Jakub Hrozek > > >> >>> > >> > > > > wrote: > > >> >>> > >> > > > > > On Wed, Jul 27, 2016 at 12:22:46PM +0200, Lukas > > >> >>> > >> > > > > > Slebodnik wrote: > > >> >>> > >> > > > > > > On (27/07/16 12:08), Jakub Hrozek wrote: > > >> >>> > >> > > > > > > > On Wed, Jul 27, 2016 at 12:02:24PM +0200, Jakub > > >> >>> > >> > > > > > > > Hrozek wrote: > > >> >>> > >> > > > > > > > > On Wed, Jul 27, 2016 at 11:54:16AM +0200, Lukas > > >> >>> > >> > > > > > > > > Slebodnik wrote: > > >> >>> > >> > > > > > > > > > ehlo, > > >> >>> > >> > > > > > > > > > > > >> >>> > >> > > > > > > > > > attached patch fixes acces denied after > > >> >>> > >> > > > > > > > > > activating user in 389ds. > > >> >>> > >> > > > > > > > > > Jakub had some comments/ideas in ticket but I > > >> >>> > >> > > > > > > > > > think it's better to discuss > > >> >>> > >> > > > > > > > > > about virtual attributes and timestamp cache > > >> >>> > >> > > > > > > > > > on mailing list. > > >> >>> > >> > > > > > > > > Yes, so the comment I have is that while this > > >> >>> > >> > > > > > > > > works, it might break some > > >> >>> > >> > > > > > > > > strange LDAP servers. > > >> >>> > >> > > > > > > > > > > >> >>> > >> > > > > > > > > We use modifyTimestamp as a 'positive' > > >> >>> > >> > > > > > > > > indicator that the entry has not > > >> >>> > >> > > > > > > > > changed -- if the modifyTimestamp didn't > > >> >>> > >> > > > > > > > > change, we consider the cached > > >> >>> > >> > > > > > > > > entry the same as what is on the server and > > >> >>> > >> > > > > > > > > only bump the timestamp > > >> >>> > >> > > > > > > > > cache. If the timestamp is different, we do a > > >> >>> > >> > > > > > > > > deep-comparison of cached > > >> >>> > >> > > > > > > > > attribute values with what is on the LDAP > > >> >>> > >> > > > > > > > > server and write the sysdb > > >> >>> > >> > > > > > > > > cache entry only if the attributes differ. > > >> >>> > >> > > > > > > > > > > >> >>> > >> > > > > > > > > I was wondering if we can use the > > >> >>> > >> > > > > > > > > modifyTimestamp at all, then, because > > >> >>> > >> > > > > > > > > even if it's the same, we might want to check > > >> >>> > >> > > > > > > > > the attributes to see if > > >> >>> > >> > > > > > > > > some of the values are different because some > > >> >>> > >> > > > > > > > > of the attributes might be > > >> >>> > >> > > > > > > > > this operational/virtual attribute.. > > >> >>> > >> > > > > > > > Sorry, sent too soon. > > >> >>> > >> > > > > > > > > > >> >>> > >> > > > > > > > I think the questions are -- 1) can we enumerate > > >> >>> > >> > > > > > > > the virtual attributes? > > >> >>> > >> > > > > > > That might be a question for 389-ds developers. > > >> >>> > >> > > > > > > But it's very likely it will be different on other > > >> >>> > >> > > > > > > LDAP servers. > > >> >>> > >> > > > > > > > > >> >>> > >> > > > > > > > 2) Would different LDAP servers have different > > >> >>> > >> > > > > > > > virtual attributes. > > >> >>> > >> > > > > > > > > > >> >>> > >> > > > > > > > For 2) maybe a possible solution might be to set > > >> >>> > >> > > > > > > > a non-existing > > >> >>> > >> > > > > > > > modifyTimestamp attribute value, but I would > > >> >>> > >> > > > > > > > consider that only a > > >> >>> > >> > > > > > > > kludge, we shouldn't break existing setups.. > > >> >>> > >> > > > > > > I am not satisfied with this POC solution either. > > >> >>> > >> > > > > > > > > >> >>> > >> > > > > > > So should we remove usage of modifyTimestamp for > > >> >>> > >> > > > > > > detecting changes? > > >> >>> > >> > > > > > I would prefer to ask the DS developers before > > >> >>> > >> > > > > > removing it completely. > > >> >>> > >> > > > > > > > >> >>> > >> > > > > > At least for large groups it might take a long time > > >> >>> > >> > > > > > to compare all attribute > > >> >>> > >> > > > > > values and IIRC we don't depend on any virtual > > >> >>> > >> > > > > > attributes for groups. Maybe > > >> >>> > >> > > > > > we could parametrize that part of the code and enable > > >> >>> > >> > > > > > the fast way with > > >> >>> > >> > > > > > modifyTimestamps for 'known' server types, that is > > >> >>> > >> > > > > > for setups with AD and > > >> >>> > >> > > > > > IPA providers. > > >> >>> > >> > > > > > > > >> >>> > >> > > > > > For users, there is typically not as many attributes > > >> >>> > >> > > > > > so we should be > > >> >>> > >> > > > > > fine deep-comparing all attributes. > > >> >>> > >> > > > > I'm adding Thierry (so please reply-to-all to keep him > > >> >>> > >> > > > > in the thread). > > >> >>> > >> > > > > > > >> >>> > >> > > > > Thierry, in the latest sssd version we tried to add a > > >> >>> > >> > > > > performance > > >> >>> > >> > > > > improvement related to how we store SSSD entries in the > > >> >>> > >> > > > > cache. The short > > >> >>> > >> > > > > version is that we store the modifyTimestamp attribute > > >> >>> > >> > > > > in the cache and > > >> >>> > >> > > > > when we fetch an entry, we compare the entry > > >> >>> > >> > > > > modifyTimestamp with what > > >> >>> > >> > > > > is on the server. When the two are the same, we say > > >> >>> > >> > > > > that the entry did > > >> >>> > >> > > > > not change and don't update the cache. > > >> >>> > >> > > > > > > >> >>> > >> > > > > This works fine for most attributes, but not for > > >> >>> > >> > > > > attributes like > > >> >>> > >> > > > > nsAccountLock which do not change modifyTimestamp when > > >> >>> > >> > > > > they are > > >> >>> > >> > > > > modified. So when an entry was already cached but then > > >> >>> > >> > > > > nsAccountLock > > >> >>> > >> > > > > changed, we treated the entry as the same and never > > >> >>> > >> > > > > read the new > > >> >>> > >> > > > > nsAccountLock value. > > >> >>> > >> > > > > > > >> >>> > >> > > > > To fix this, I think we have several options: > > >> >>> > >> > > > > 1) special-case the nsAccountLock. This seems a > > >> >>> > >> > > > > bit dangerous, > > >> >>> > >> > > > > because I'm not sure we can say that some other > > >> >>> > >> > > > > attribute we are > > >> >>> > >> > > > > interested in behaves the same as nsAccountLock. > > >> >>> > >> > > > > 2) drop the modifyTimestamp optimization > > >> >>> > >> > > > > completely. Then we fall > > >> >>> > >> > > > > back to comparing the attribute values, which > > >> >>> > >> > > > > might work, but for > > >> >>> > >> > > > > huge objects like groups with thousands of > > >> >>> > >> > > > > members, this might be > > >> >>> > >> > > > > too expensive. > > >> >>> > >> > > > > 3) only use the modifyTimestamp optimization for > > >> >>> > >> > > > > cases where we know > > >> >>> > >> > > > > we don't read any virtual attributes. > > >> >>> > >> > > > > > > >> >>> > >> > > > > And my question is -- can we, in general, know if the > > >> >>> > >> > > > > modifyTimestamp > > >> >>> > >> > > > > way of detecting changes is realiable for all LDAP > > >> >>> > >> > > > > servers? Or do you > > >> >>> > >> > > > > think it should only be used for cases where we know we > > >> >>> > >> > > > > are not > > >> >>> > >> > > > > interested in any virtual attributes (that would mostly > > >> >>> > >> > > > > be storing > > >> >>> > >> > > > > groups from servers where we know exactly what is on > > >> >>> > >> > > > > the server side, > > >> >>> > >> > > > > like IPA or AD). > > >> >>> > >> > > > Hello, > > >> >>> > >> > > > > > >> >>> > >> > > > Relying on modifytimestamp looks a good idea. Any > > >> >>> > >> > > > MOD/MODRDN will update it, > > >> >>> > >> > > > except I think it is unchanged when updating some > > >> >>> > >> > > > password policy > > >> >>> > >> > > > attributes. > > >> >>> > >> > > > > > >> >>> > >> > > > Regarding virtual attribute, the only one I know in IPA > > >> >>> > >> > > > is nsaccountlock. > > >> >>> > >> > > > nsaccountlock is an operational attribute (you need to > > >> >>> > >> > > > request it to see it) > > >> >>> > >> > > > and is also a virtual attribute BUT only for 'staged' and > > >> >>> > >> > > > 'deleted' users. > > >> >>> > >> > > > It is a stored attribute for regular users and we should > > >> >>> > >> > > > update > > >> >>> > >> > > > modifytimestamp when it is set. > > >> >>> > >> > > > > > >> >>> > >> > > > thanks > > >> >>> > >> > > > thierry > > >> >>> > >> > > OK, in that case it seems like we can special-case it. But > > >> >>> > >> > > do you know > > >> >>> > >> > > about any other attributes in any other LDAP servers? > > >> >>> > >> > Any LDAP server following standard should provide > > >> >>> > >> > modifytimestamp that > > >> >>> > >> > reflect the last update of the entry. Now virtual attribute > > >> >>> > >> > values may be > > >> >>> > >> > "attached" to the entry and its value change without > > >> >>> > >> > modification of > > >> >>> > >> > modifytimestamp. > > >> >>> > >> > For 389-ds and IPA it is fine as virtual value of > > >> >>> > >> > nsaccountlock is changed > > >> >>> > >> > only when the DN change. > > >> >>> > >> > For others LDAP servers I suppose it exists the same ability > > >> >>> > >> > to define > > >> >>> > >> > service providers that return virtual attribute values. The > > >> >>> > >> > difficulty is > > >> >>> > >> > that the schema may not give any hint if the retrieved > > >> >>> > >> > attributes values > > >> >>> > >> > were stored or computed and consequently trust > > >> >>> > >> > modifytimestamp to know if > > >> >>> > >> > the values changed or not. > > >> >>> > >> > For example in ODSEE, memberof is a virtual attribute. > > >> >>> > >> Thank you, for the explanation Thierry. > > >> >>> > >> > > >> >>> > >> Then to be on the safe side I propose: > > >> >>> > >> 1) We add an (probably undocumented?) flag that says > > >> >>> > >> whether to use > > >> >>> > >> modifyTimestamp to detect entry changes or not > > >> >>> > >> 2) for the generic LDAP provider we always really compare > > >> >>> > >> the > > >> >>> > >> attribute values, in other words the option would be > > >> >>> > >> set to > > >> >>> > >> false. If there is anyone with performance issues with > > >> >>> > >> a generic > > >> >>> > >> setup, we tell them to flip the option. > > >> >>> > >> 3) For the IPA and AD providers, we set this option to > > >> >>> > >> true and use > > >> >>> > >> the modifyTimestamp value to detect changes > > >> >>> > >> 4) We special case nsAccountLock > > >> >>> > >> > > >> >>> > >> Lukas, do you agree? > > >> >>> > >Hi Jakub, > > >> >>> > > > > >> >>> > >digging further into the server, it appears that a DS plugin > > >> >>> > >'acctpolicy' > > >> >>> > >updates an entry without changing the mofidytimestamp. > > >> >>> > >The updated attribute is 'lastlogintime' (by default) but i think > > >> >>> > >can be any > > >> >>> > >attribute configured in the entry account policy. > > >> >>> > >I need to do further tests to confirm this. > > >> >>> > > > > >> >>> > > > >> >>> > IMHO, the problems with nsAccountLock just revealed the fact that > > >> >>> > it might happen that the attribute modifyTimestamp/whenChanged > > >> >>> > needn't be > > >> >>> > a reliable way how to determine change in entry for any LDAP > > >> >>> > Server. > > >> >>> > > > >> >>> > We improved the performance but there might be other corner cases > > >> >>> > with > > >> >>> > other LDAP servers. > > >> >>> > > > >> >>> > Jakub proosed in 2) that we should always really compare the the > > >> >>> > attibutes > > >> >>> > from sssd cache and from LDAP search. But it would mean that we > > >> >>> > would not > > >> >>> > improve a performance for generic LDAP providers. > > >> >>> > > >> >>> We would still avoid the cache writes, "only" after comparing the > > >> >>> attribute values. So essentially by using the modifyTimestamp we > > >> >>> save a > > >> >>> single LDB base search and a number of attribute-value comparisons, > > >> >>> depending on how large the object is. > > >> >>> > > >> >>> > > > >> >>> > We cannot generally detect virtual attributes for any LDAP server. > > >> >>> > What about adding an option where user could list virtual > > >> >>> > attributes. > > >> >>> > It would be a kind of proposed solution 4) but it would not be a > > >> >>> > special case for nsAccountLock but for more attributes which could > > >> >>> > be changed > > >> >>> > in configuration. > > >> >>> > > >> >>> OK, so your proposal is to keep the more aggressive cache > > >> >>> optimization? > > >> >>> I think I'm mostly afraid about the more exotic LDAP servers, like > > >> >>> IBM > > >> >>> Tivoli or Novell eDirectory which I already know from experience > > >> >>> don't > > >> >>> follow the established standards closely. I guess I'm fine with > > >> >>> that, we > > >> >>> can always flip the default back. Worst case for people who start > > >> >>> using > > >> >>> 1.14, the admin can always define modifyTimestamp to some > > >> >>> non-existing > > >> >>> attribute and force the attribute value comparison check. > > >> >>> > > >> >>> Yes, we can make the list configurable. We also need to be > > >> >>> very careful about printing the reason for (not) updating the cache > > >> >>> to > > >> >>> the admin (#3060). > > >> >> > > >> >>OK, so after some discussion with Simo on IRC, there is a different > > >> >>proposal - let responder control the optimization level, so that PAM > > >> >>responder would always trigger a full cache write, or at least > > >> >>deep-compare the attributes and NSS responder would rely on > > >> >>modifyTimestamp. > > >> >> > > >> >>But that's a larger fix, so for short-term fix I propose to only use > > >> >>modifyTimestamp for group objects and always compare attributes for > > >> >>users. Then later, as another patch we can let the responder send a > > >> >>flag > > >> >>to control the optimization (would probably be done as a flag for a > > >> >>sysdb transaction). > > >> >> > > >> >>If you agree, I would file a ticket for the second part and you can > > >> >>instead write a patch to disable modifyTimestamp checks for users. > > >> > > > >> >As you wish. > > >> >The updated patch is attached. > > >> > > > >> >LS > > >> > > >> >From ae01ffdbbc74c5b43c2b644f8847d856cd2bf997 Mon Sep 17 00:00:00 2001 > > >> >From: Lukas Slebodnik <lsleb...@redhat.com> > > >> >Date: Wed, 3 Aug 2016 18:48:04 +0200 > > >> >Subject: [PATCH] SYSDB: Avoid optimisation with modifyTimestamp for > > >> >users > > >> > > > >> >The usage of modifyTimestamp needn't be a reliable way > > >> >for detecting of changes in user entry in LDAP. > > >> >The authorisation need to rely current data from LDAP > > >> >and therefore we will temporary disable optimisation with > > >> >modifyTimestamp and we will rather rely on deep comparison > > >> >of attributes. In he future, it might be changed and > > >> >responders might control the optimization level. > > >> > > > >> And now with version witout failures in unit test and without compiler > > >> warnings > > >> :-) > > >> > > >> LS > > > > > >Hi, > > > > > >this patch doesn't apply atop origin/master, do I need some patches > > >before this one? > > > > I looks like I created patch on top of your patch > > [SSSD] [PATCH] SYSDB: Fix setting dataExpireTimestamp if sysdb is supposed > > to > > set the current time > > > > If you want I can create on origin/master but you would need to rebase your > > patch. So it depends on wich patch will be pushed the first > > I don't mind waiting and testing the patches together. I take it you'll > review my patch, then?
Hmm, this still doesn't work: jhrozek@hendrix devel/sssd (review %) » git reset --hard origin/master HEAD is now at 2a03170 Fixed some typos in man pages jhrozek@hendrix devel/sssd (review %) » git am 0001-SYSDB-Fix-setting-dataExpireTimestamp-if-sysdb-is-su.patch Applying: SYSDB: Fix setting dataExpireTimestamp if sysdb is supposed to set the current time jhrozek@hendrix devel/sssd (review %) » git am 0001-SYSDB-Avoid-optimisation-with-modifyTimestamp-for-us.patch Applying: SYSDB: Avoid optimisation with modifyTimestamp for users error: patch failed: src/db/sysdb_ops.c:2465 error: src/db/sysdb_ops.c: patch does not apply Patch failed at 0001 SYSDB: Avoid optimisation with modifyTimestamp for users The copy of the patch that failed is found in: /home/remote/jhrozek/devel/sssd/.git/rebase-apply/patch When you have resolved this problem, run "git am --continue". If you prefer to skip this patch, run "git am --skip" instead. To restore the original branch and stop patching, run "git am --abort". _______________________________________________ sssd-devel mailing list sssd-devel@lists.fedorahosted.org https://lists.fedorahosted.org/admin/lists/sssd-devel@lists.fedorahosted.org
