On 08/02/2012 11:17 AM, Stephen Ingram wrote:
On Wed, Aug 1, 2012 at 7:35 AM, Simo Sorce<s...@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<pspa...@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.

We have a "somewhat" reproducible test case - see https://bugzilla.redhat.com/show_bug.cgi?id=845125 - note that the problem only seems to occur on RHEL 6.3 with the latest Z-stream packages.


Steve

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