On Mon, Oct 02, 2017 at 06:21:05PM +0000, Galen Johnson wrote:
?Did this make it to the list? I really wish I could see my own
From: Galen Johnson
Sent: Thursday, September 28, 2017 3:28 PM
To: End-user discussions about the System Security Services Daemon
Subject: Fw: sssd email login performance
Adding the list since Sumit appears to be busy. The info is anonymized so it should be
ok. Hopefully, the gz file makes it through.
I'm sorry for the delay (in responding). So far I had a short look at
the logs and the lookup scheme is currently as expected. There are
currently several reasons which cause the observed delay.
One is that currently the lookups by email address are not added to the
memory cache in a way that a second lookup by email address can use it.
As a result the request always has to be processed by SSSD's nss
responder. (Currently I'm working on improving this so that the memory
cache can be used here as well).
Another is that in a setup with multiple domains, e.g. an AD forest, it
is not clear where the email address is coming from. What makes it worse
is that the domain part of the email address can match a domain in a
forest but the user with that email address might come from a completely
different domain. That is why SSSD first assumes that the input is a
fully-qualified name and then falls back to assuming an email address.
And here the backend has to search in each domain for the email
address. When lookup up the entry in the on-disk cache this can be done
in a single search.
I'll have a closer look at the logs tomorrow to see if there is
something which can be tuned for your setup.
From: Galen Johnson
Sent: Thursday, September 21, 2017 5:36 PM
To: Sumit Bose
Cc: Philip Holman
Subject: sssd email login performance
I'm finally getting a chance to follow up on the email thread (of the same title)
from the sssd list. We've seen some delays (multi-second) for auth requests when
users use their email address versus their id. I've attached a tar file with several
log files. Phil may need to explain the summary file if you have any questions about it.
We are running Centos 7.4 now but I'm fairly certain that it's the same binaries
as RHEL 7.4. These logs were taken while on 7.3. I noticed that sssd bumped to 1.15 with
Some outstanding questions we have are:
1. The cache appears to not be used for the email attribute. Why is this not used?
2. We're also curious why the ldap requests add 2 seconds when performing the same
query from the command-line returns almost immediately.
3. Is it possible to have SSSD ignore the domain and just immediately look up the
address? We see "is_email_from_domain" in the domain log (reflected in the nss
log). We checked the man pages and nothing really jumped out as a config option.
It should be noted that we also moved the sssd db cache to tmpfs (per a blog from
Thanks for any insight
Phil's analysis follows:
To wrap up, I took one more look at one of the very slow email logins to pull out a trace
of what it was doing. The attached files are the log snippets with line breaks marking off
the incoming requests to make it more clear what each module was servicing when. The
summary.txt shows the summarized entry for the connection and also gives an abridged
combined view of the logs marking where the 7 seconds appear to have gone. So this seemed
enough info to share if we have the opportunity for a consult with someone.
The short version is that 1 second roughly went to the bind that tests the user, but the
other 6 appear to have likely been the result of interacting with local caches rather than
the DCs. So that makes the cache files and related configuration look suspicious. It also
makes more sense that our earlier checks (against logs or live tests) of the Exnet
interactions have failed to show any latency issues on those step.
Possibly the fiddling we've already done with the cache files and cache config
resolved this, but it is probably still worth passing this along to someone knowledgeable
who might be able to explain what about the setup likely made everything go sideways.
Otherwise, we might be facing some kind of build-up pattern where it will always look rosy
after a restart and gradually degrade over time as state builds up.
It might also be a good idea to bounce and clear out sssd/pam state on the weekly
restarts just to protect against any possible build-up (unless we want to intentionally
avoid that for now to see if it does degrade over time).
sssd-users mailing list -- sssd-users(a)lists.fedorahosted.org
To unsubscribe send an email to sssd-users-leave(a)lists.fedorahosted.org