[Freeipa-devel] slow response

[Simo Sorce]

On Thu, 2012-08-02 at 10:17 -0700, Stephen Ingram wrote:
> On Wed, Aug 1, 2012 at 7:35 AM, Simo Sorce <simo at redhat.com> wrote:
> > On Tue, 2012-07-31 at 08:49 -0700, Stephen Ingram wrote:
> >> On Tue, Jul 31, 2012 at 1:39 AM, Petr Spacek <pspacek at redhat.com> wrote:
> >> > On 07/31/2012 12:27 AM, John Dennis wrote:
> >> >>
> >> >>
> >> >> What is taking so long with session bookkeeping? I don't know yet. I would
> >> >> need more timing instrumentation. I will say when I looked at the
> >> >> python-krb5
> >> >> code (which we use to populate the ccache from the session and read back
> >> >> to
> >> >> store in the session) seemed to be remarkably inefficient. We also elected
> >> >> to
> >> >> use file based ccache rather than in-memory ccache (that means there is a
> >> >> bit
> >> >> of file-IO occurring).
> >> >
> >> >
> >> > A note regarding python-krbV:
> >> > I used python-krbV extensively in my thesis for KDC stress test. Python-krbV
> >> > can obtain several thousands of TGTs per second (even with ccache in a
> >> > file). AFAIK VFS calls are not done synchronously. But others parts of
> >> > python-krbV were left uncovered, so it can contain some surprises.
> >> >
> >> > === Wild speculation follows ===
> >> > 1.5 second is incredibly long time, it sounds like some kind of timeout.
> >> > Krb5 libs have usual timeout = 1 second per request.
> >> >
> >> > Are all KDCs in /etc/krb5.conf alive and reachable?
> >>
> >> In this case, as I'm referring to the extreme slowness of the Web UI,
> >> the KDC is on the same system (the ipa server) that is making the
> >> request, correct?
> >>
> >> > Is SSSD running on problematic server?
> >>
> >> Yes. Again, I'm guessing the problematic server is the IPA server itself.
> >>
> >> > Is proper KDC selected by SSSD KDC auto-locator plugin?
> >> > (See /var/lib/sss/pubconf/)
> >>
> >> Yes, I checked that file and it is the IP address of the IPA server on
> >> the same server. Perhaps should this be 127.0.0.1 instead?
> >>
> >> I also have checked the resolv.conf file, and indeed the IP points to
> >> the IPA server itself (same machine) as expected. Both forward and
> >> reverse DNS work. I'm not really sure what else could be setup
> >> incorrectly to cause any KDC slowness.
> >>
> >> Due to the extreme UI slowness issue, I have not created any replicas
> >> so this system is it. I'm not so sure I would be able to see the 1.5 s
> >> delay if it weren't compounded by the overall slowness of the Web UI,
> >> however, the KDC seems to perform well for other systems in the realm.
> >> I'm certainly not taxing it with a huge load, but tickets seem to be
> >> issued without delay.
> >
> > Stephen,
> > another user sent me a wireshark trace for a similar performance issue.
> > So far I see a pause when doing the first leg of a SASL authentication.
> > This may well explain also your issue.
> >
> > Can you test connecting to the ldap server using ldapsearch -Y GSSAPI
> > (you need a kerberos ticket) and telling me if you experience any
> > delay ?
> > If you could run a bunch of searches in a loop and take a wireshark
> > trace that may help analyzing the timings and seeing if there is a
> > correlation.
> 
> I've done this. It looks like this delay has been uncovered already
> though? I can still send you the dump privately if you think it would
> help.

I think we reproduced it, can you confirm you are also running on RHEL ?
So far it seem the only platfrom we can reproduce is RHEL 6.3

Simo.

-- 
Simo Sorce * Red Hat, Inc * New York