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Re: slow cn=config changes; Re: Correct procedure to backup LDAP?
Howard Chu wrote:
Eric Irrgang wrote:
I'm trying to migrate to a reliable live update mechanism and I have
tried using slapcat after putting the directory into read-only mode,
but that seems to bring up additional issues.
In OL 2.3.24 with hdb, how supported is it to do the following?
It seems to work, usually in about a second, but sometimes can take
upwards of a minute, during which time the directory seems to be in
some sort of stop-the-world state where connections just hang,
preventing it from being the non-intrusive backup approach I'd hoped
for. The CPU usage doesn't spike and the disk usage appears normal.
I've seen similar behavior with other cn=config changes.
Has anyone else encountered this? Is it supposed to work better?
Any ideas what might be going on or what I should look for? There
don't seem to be any runaway polling loops or lwp fights going on. A
truss shows a little bit of lwp polling activity and some writes
going on, but nothing suspicious like the hang early in 2.3.x when
shutting down with gentlehup.
This sounds pretty normal. When you issue a modify on cn=config, it
suspends the thread pool. That means that no new operations can start,
and cn=config waits for any currently running operations to finish,
then it does the modification you requested. The busier the server,
the longer you have to wait before that modification can execute.
I should note that for this specific example, you can also set readonly
mode using cn=monitor, which has no particular impact on the thread
pool, so it should take effect immediately.
-- Howard Chu
Chief Architect, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc
OpenLDAP Core Team http://www.openldap.org/project/