Interesting and good information. We happen to use Big Brother/Xymon
for monitoring and have multiple scripts to check things like cache,
locks etc. We will get notified when these sense a problem, but at 1AM
on a Saturday getting notified and fixing the issue before all those
services get impacted is a little scary. That's why we were
contemplating that maybe it would be wise to "hit it with a hammer"
until we are able to intervene and repair.
On Wed, 30 Mar 2011 18:43 -0400, "Aaron Richton"
So, the best defense is a good offense in this case, and if you were
running 2.4.25 with the appropriate BerkeleyDB library you'd likely not
see an issue of this manner.
With that said, there was a time (with earlier releases of OpenLDAP) when
we had this issue (one bdb go down, with the service apparently working
via an overly simple smoke test). Not being fans of being bitten by the
same failure mode twice, we wrote up a Nagios check that searches a
known-present-on-disk entry that is in each of our databases. (You can
either create one, or (ab)use "ou=People" if you're RFC2307 or use
"cn=Manager" or what have you...) If any database doesn't return a hit,
time for us to get a call.
As an aside, I find this thoroughly fascinating timing. Not that it'll
make you feel any better in the present case, but I was just considering
writing something up for the next LDAPCon on how we do monitoring (there
are ~10 angles we check from, many of them due to real life situations
similar to yours). They're all relatively simple ideas like the above,
I suppose cleaning up our code to the point where it's world-safe and
getting something written up on it may be useful. They've proven
occasionally useful for slapd(8) code issues and also, more frequently,
useful in the face of human factors.
On Wed, 30 Mar 2011, ldap@mm">email@example.com wrote:
> A while ago I posted that we were having what we thought were random bdb
> backend crashes with the following in our log:
> bdb(o=example.com): PANIC: fatal region error detected; run recovery.
> This was on a on our RH5 openldap servers (2.3.43) that we were
> It appears that the crashes were caused by a vulnerability scanner that
> was hitting the server (still testing), even though it was suppose to be
> safe. We'll have to investigate what is causing it, maybe we will need
> an acl to stop whatever the scanner is doing. Once we stopped the
> automated scan, the servers seem to be running as expected.
> But, this brought up another issue. When the bdb backend failed, the
> slapd process continued run and listen on the ldap ports and clients
> still tried to connect to the failed server for authentication. The
> server accepted and established the connection with the client. Of
> course the client could not authenticate since the backend db was down.
> The client will not fail over to the other server that is listed in it's
> ldap.conf file since it thinks it has a valid connection. If the slap
> process is not running then the fail over works fine since no ports are
> there for the client to connect to.
> I'm thinking that bdb failures will be rare once we solve the scanner
> issue, but on a network that relies heavily on ldap, a failed bdb
> backend with a running slapd would cause significant issues.
> Just trying to restart the slapd service doesn't fix the issue, a manual
> recovery is required (slapd_db_recover). I was curious if anyone has
> put something in place to deal with this potential issue? Maybe run
> slapd_db_status via cron and if it errors due a bdb corruption, just
> stop slapd and let the admin know. At least the clients would be able
> to failover to the other ldap servers. I guess an automated recovery is
> possible via a script, but I'm not sure if that's a good idea. Maybe
> dealing with this type of failure is not really required, I was hoping
> that some of you that have been do this for a while would have some