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Re: (ITS#6322) slapd suddenly stops working, and starts using 100% CPU
- To: openldap-its@OpenLDAP.org
- Subject: Re: (ITS#6322) slapd suddenly stops working, and starts using 100% CPU
- From: firstname.lastname@example.org
- Date: Fri, 2 Oct 2009 20:54:29 GMT
- Auto-submitted: auto-generated (OpenLDAP-ITS)
> Full_Name: Helge Milde
> Version: slapd 2.4.11
> OS: Debian 5
> Submission from: (NULL) (126.96.36.199)
> In the last two days, slapd has randomly stopped working on our server, about
> one time every two or three hours. Before this, slapd had been running without
> any problems for about two months. slapd.conf has not been touched since then.
> What happens is that slapd stops taking queries (postfix, dovecot, NSS etc.
> starts getting timeouts), and it starts using exactly 100% of one core until we
> restart it.
> After restart, everything works again (until this happens again).
> It seems to only happen when slapd is under "stress" (we have an 8-core system
> with 8G RAM, and so slapd is really never under much "stress"; the biggest CPU
> load I've seen is about 40% on one core). The last ldap search before slapd
> stops working is always the same:
> Oct 2 10:57:38 oi-mail slapd: conn=1543 op=1 SRCH
> base="ou=groups,dc=web,dc=xxxx,dc=net" scope=1 deref=0
> .. which should return about 1800 entries. Different connections might query
> this simultaneously, and it's a query that happens every ~10 seconds on
> I've tried to reproduce this by doing ..
> # while [ 1 ]; do ldapsearch -x -H ldaps://.. -b
> 'ou=groups,dc=web,dc=xxxx,dc=net' '(&(objectClass=posixAccount))'; done
> .. for two minutes without any "luck" :). slapd just uses a bit more CPU, but
> never stops working.
> With "loglevel stats stats2", I get nothing out of the logs:
> Oct 2 08:42:15 oi-mail slapd: conn=34798 op=1 ENTRY
> ... time of "crash" (we're mid-search at this point); nothing gets logged until
> we do a restart: ...
> Oct 2 08:42:30 oi-mail slapd: daemon: shutdown requested and initiated.
> Oct 2 08:42:30 oi-mail slapd: conn=34391 fd=31 closed (slapd shutdown)
> ... many entires like the one above, and then I seem to be getting the next
> entry from the same connection, right before it closes: ...
> Oct 2 08:42:30 oi-mail slapd: conn=34798 op=1 ENTRY
> Oct 2 08:42:30 oi-mail slapd: conn=34798 fd=81 closed (slapd shutdown)
> I've tried logging more than just stats, but the interesting loglevels also
> causes a big performance hit (trace and args), and I'm not really sure which of
> the other loglevels could be helpful.
> This is a live ldap server, on a server that also hosts other services, so I
> simply can't take the performance hit.
> I also did a strace -p<slapd pid>, which only gives "futex(0x41c499e0,
> FUTEX_WAIT," until I restart slapd, but the "restarting routine" could be
> useful, so here it is: http://www.pastie.org/639170
strace is useless. Use gdb and get a trace of all running threads when this
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/