On Mon, Aug 26, 2013 at 04:02:59PM -0400, Simo Sorce wrote:
On Mon, 2013-08-26 at 21:41 +0200, Jakub Hrozek wrote:
> On Mon, Aug 26, 2013 at 03:35:09PM -0400, Simo Sorce wrote:
> > On Mon, 2013-08-26 at 21:17 +0200, Jakub Hrozek wrote:
> > > On Mon, Aug 26, 2013 at 06:18:05PM +0200, Sumit Bose wrote:
> > > > On Mon, Aug 26, 2013 at 05:20:21PM +0200, Jakub Hrozek wrote:
> > > > > On Fri, Aug 23, 2013 at 03:44:09PM +0200, Sumit Bose wrote:
> > > > > > Hi,
> > > > > >
> > > > > > currently in ipa-server-mode only the AD groups memberships
are
> > > > > > available. This patch adds the IPA group memberships to
trusted AD
> > > > > > users.
> > > > > >
> > > > > > This patch is missing some unit tests for some of the
helper functions.
> > > > > > I will send them later, but I didn't want to delay the
next release.
> > > > > >
> > > > > > bye,
> > > > > > Sumit
> > > > >
> > > > > I haven't done any testing yet but do we need the timeout?
Since the
> > > > > initgroups is a rare operation and on logins we generally want
to have
> > > > > the correct memberships, can we just rely on responder caching?
> > > >
> > > > I was thinking of situations where multiple logins happen in a short
> > > > time. Additionally I think even if group memberships of a user might
> > > > change often the mapping of AD to IPA group memberships via the
external
> > > > groups will only change rarely.
> > > >
> > > > Maybe we can a cache time option to make it more flexible?
> > > >
> > > > bye,
> > > > Sumit
> > >
> > > I was thinking about this more on my way home and I think you're
> > > right we need to optimize the ipa_server_mode. This could cause the
"8AM
> > > login rush" to be a real bottleneck.
> > >
> > > But I think we can exploit the fact that we know the server well during
> > > the ipa_server_mode. What about this approach?
> > > 1. on startup we download all external groups
> >
> > it could be a huge set, and would cause a huge load if someone runs a
> > puppet script to reconfigure and restart a few 1000 machines with sssd.
> >
>
> A huge set of external groups?
Why not ?
No technical reason. I just don't see that as a common use-case that's
all.
> > > 2. store the largest lastUSN to the server mode context
> >
> > we already have this afaik
>
> No we don't. This is new code just for the server mode.
Ahh, that explains some things, sorry.
No problem, lot of patches are flailing around, I know.
> >
> > > 3. on subsequent lookups, only download and store groups with higher
> > > lastUSN
> >
> > if you change server you are back to square zero though
> >
>
> Which is never during in the server mode. (except for slapd outages etc)
>
> > > 4. perform the lookup always. It's on the server after all so
> > > network LDAP search is quite cheap.
> >
> > not sure I understand what this means ?
>
> The current patch re-downloads external groups every 600 seconds and if
> 600 seconds hasn't passed, uses cache. I'm proposing we download
> (&(objectClass=externalGroup)(lastUSN>=stored_last_usn)) on every
> request because in the server mode the latency is not an issue.
600 is a lot :(
yes, that's why I was trying to come up with something more optimized..
> >
> >
> > The point of checking initgroups at login is to assure the right
> > memberships are in place, both for security reasons and to allow a user
> > to logoff and login back again and make sure eh gets new group
> > memberships if he has been granted any new ones.
> >
> > Loggin off then back on is the only way to gain system-wide the new
> > memberships so that's what an administrator will tell a user to do if
> > the user complains he can't access something.
> >
> > This means that caching can't last long as the side effects are severe.
> > So anything more than a few seconds would probably be bad. A few seconds
> > make total sense for load issues when someone is abusing pam atuh (for
> > example someon eusing basic auth wired to pam auth for a a web server
> > that will receive potentially many tens of authentications for the same
> > user within a fraction of a second as each image and file is loaded in a
> > new connection).
> >
> > In this case you really want to completely cache the whole operation and
> > not touch the network for any reason, otherwise latency will make things
> > unbearable. But that's the extent to which you want to go, a few seconds
> > for auth bursts, nothing more.
> >
> > Simo.
>
> The latency in the server mode is really small, we should always be
> talking to the local server.
I think we shouold defer this until the synrepl control is available in
389ds, then we can simply have a persistent search open using syncrepl
and we'll get changes as needed and no more that that (including
deletions).
Simo.
Yes, that sounds like a very good solution, I just think we also need to
have a way to handle the external groups in time for 1.11/3.3. If we can
leverage a 389DS control later, even better.