[Freeipa-devel] slow response

[Stephen Ingram]

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.

Steve