On 9/13/23 09:57, Julian Kippels wrote:
Hi Thierry,
> First you may install debuginfo it would help to get a better
> understanding what happens.
I will try to do that the next time it breaks. Unfortunately this is a
production machine and I can't always take the time to do forensics.
Sometimes I just have to quickly get it up running again and just
restart the service completely. I have not yet found a way to trigger
this in my lab environment.
> Do you know if it recovers after that high CPU peak ?
So far it has never recovered. I have seen the high CPU peak 7 or 8
times now and it is always like this:
1. CPU usage peaks on 2 threads
ATM I assume it would be a MOD eating CPU while writing back to the
changelog + trickling. You may get pstacks + top -H to confirm this
2. Admin from external server tells me that his system cannot do LDAP
operations anymore.
stacktrace shows many updates waiting for the above MOD to complete. In
extreme case, the pending MODs may exhaust workers make the server
unresponsive
3. I try to do some ldapmodify operations, which succeed and get
replicated correctly.
This is surprising, I would expect a MOD, on the server where a MOD is
busy on CL, to hang as well. Are you doing your update on the same backend ?
4. At this point there are 2 options:
a. Both the admin from the external server and I restart our
services which temporarily fixes the issue
b. I don't restart my system and after a few hours (where the CPU
peak does not go away) dirsrv completely freezes up and does not
accept any connections anymore.
You may look at the started MOD in the access log and check which one
was hanging. Then compare its etime (using the csn) on the others servers.
Does it occur always on the same server ?
regards
thierry
> Regarding the unindexed search, you may check if 'changeNumber' is
> indexed (equality). It looks related to a sync_repl search with no
> cookie or old cookie. The search is on a different backend than Thread
> 62, so there is no conflict between the sync_repl unindexed search and
> update on thread62.
The equality index is set for changeNumber. I will assume that this is
a different "problem" and has nothing to do with the high cpu load and
freezes and not look further into it for the time.
Kind regards
Julian
Am 12.09.23 um 14:21 schrieb Thierry Bordaz:
Hi Julian,
Difficult to say. I do not recall specific issue but I know we fixed
several bugs in sync_repl.
First you may install debuginfo it would help to get a better
understanding what happens.
The two threads are likely Thread 62 and trickle thread (2 to 6)
because of intensive db page update.
Do you know if it recovers after that high CPU peak ?
A possibility would be a large update to write back to the changelog.
You may retrieve the problematic csn in access log (during high cpu)
and dump the update from the changelog with dbscan (-k).
Regarding the unindexed search, you may check if 'changeNumber' is
indexed (equality). It looks related to a sync_repl search with no
cookie or old cookie. The search is on a different backend than
Thread 62, so there is no conflict between the sync_repl unindexed
search and update on thread62.
best regards
thierry
On 9/12/23 13:52, Julian Kippels wrote:
Hi,
there are two threads that are at 100% CPU utilisation. I did not
start any admin task myself, maybe it is some built-in task that is
doing this? Or could an unindexed search on the changelog be causing
this?
I have noticed this message:
NOTICE - ldbm_back_search - Unindexed search: search
base="cn=changelog" scope=1 filter="(changeNumber>=1)" conn=35871 op=1
There is an external server that is reading the changelog and
syncing some stuff depending on that. I don't know why they are
starting at changeNumber>=1, they probably should start way higher.
If it is possible that this is the cause I will kick them to stop
that ;)
I am running version 2.3.1 on Debian 12, installed from the Debian
repositories.
Kind regards
Julian
Am 08.09.23 um 13:23 schrieb Thierry Bordaz:
Hi Julian,
It looks that an update (Thread 62) is either eating CPU either is
blocked while update the changelog.
When it occurs could you run 'top -H -p <pid>' to see if some
thread are eating CPU.
Else (no cpu consumption), you may take a pstack and dump DB lock
info (db_stat -N -C A -h /var/lib/dirsrv/<inst>db)
Did you run admin task (import/export/index...) before it occurred ?
What version are you running ?
best regards
Thierry
On 9/8/23 09:28, Julian Kippels wrote:
Hi,
it happened again and now I ran the gdb-command like Mark
suggested. The Stacktrace is attached. Again I got this error
message:
[07/Sep/2023:15:22:43.410333038 +0200] - ERR - ldbm_back_seq -
deadlock retry BAD 1601, err=0 Unexpected dbimpl error code
and the remote program that called also stopped working at that time.
Thanks
Julian Kippels
Am 28.08.23 um 14:28 schrieb Thierry Bordaz:
Hi Julian,
I agree with Mark suggestion. If new connections are failing a
pstack + error logged msg would be helpful.
Regarding the error logged. LDAP server relies on a database
that, under pressure by multiple threads, may end into a db_lock
deadlock. In such situation the DB, selects one deadlocking
thread, returns a DB_Deadlock error to that thread while the
others threads continue to proceed. This is very normal error
that is caught by the server that simply retries to access the
DB. If the same thread fails to many time, it stops retry and
return a fatal error to the request.
In your case it reports code 1601 that is transient deadlock with
retry. So the impacted request just retried and likely succeeded.
best regards
thierry
On 8/24/23 14:46, Mark Reynolds wrote:
Hi Julian,
It would be helpful to get a pstack/stacktrace so we can see
where DS is stuck:
https://www.port389.org/docs/389ds/FAQ/faq.html#sts=Debugging%C2%A0Hangs
Thanks,
Mark
On 8/24/23 4:13 AM, Julian Kippels wrote:
Hi,
I am using 389-ds Version 2.3.1 and have encountered the same
error twice in three days now. There are some MOD operations
and then I get a line like this in the errors-log:
[23/Aug/2023:13:27:17.971884067 +0200] - ERR - ldbm_back_seq -
deadlock retry BAD 1601, err=0 Unexpected dbimpl error code
After this the server keeps running, systemctl status says
everything is fine, but new incoming connections are failing
with timeouts.
Any advice would be welcome.
Thanks in advance
Julian Kippels
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