Kolab2 Slapd hanging - master/slave replication issues

[Stephan Buys]

One thing to mention also is that slapd is "locking up", i.e. you have a process that
is accepting new connections, but not servicing it and just hanging. The only way
to get rid of the process is with a "kill -9 ..."

And the lockups occur on "reading" as opposed to writing. 

On Tuesday 15 March 2005 10:08, Dieter Kluenter wrote:
> Hi Stephan,
> 
> Stephan Buys <list at codefusion.co.za> writes:
> 
> > Hi all,
> >
> > Today I'm the one in need of advice :-)
> >
> > We have a big Kolab2 server with about 350 users on it and 2 slave servers
> > in remote geographic locations. The slave servers have between 50 and 100
> > users each.
> 
> These are not large numbers, in terms of directory speaking :-)
> 
> > We deployed Kolab2 on Sunday and have since had several issues:
> >
> > 1) slapd keeps on hanging. I suspect that this is due to the strain taken by
> > slapd as it needs to service, "uid requests", "mail routing", "sasl auth", etc.
> 
> Please give some more details
> - OpenLDAP versions of master and slaves
> - Contents of DB_CONFIG
> - cachesize in slapd.conf
> - idlecachsize in slapd.conf
> - indices in slapd.conf
> - database definition in slapd.conf
> - BerkeleyDB version and number of patches applied
> 
> > 2) When slapd hangs we need to do a db_recover to get it back up and running.
> > After having to run db_recover on the slave as well as the master servers the
> > databases have now become inconsistent.
> 
> A database corruption occurs only with heavy write load and
> insufficiened cache size or a flag DB_TXN_NOSYNC set in DB_CONFIG.
> 
> > So my questions:
> >
> > 1) What can I do to make slapd more robust? Pre-forking, more
> >    children processes?
> 
> That depends on your OS and hardware as well as on the number of
> connections in a given period.
> 
> > The main server is running at load average of 3 at the moment which I am sure 
> > compounds the problem...
> >
> > 2) How easy is it to re-sync the master-slave databases? Can I stop the servers,
> > copy the master dbs to the slaves and start up again?
> 
> You may slapcat the master and slapadd on the slave.
> 
> > Any tuning/optimisation tips would be greatly appreciated.
> 
> I would like to, but a few more informations would be helpful :-)
> 
> -Dieter
> 

-- 
Stephan  Buys
Code Fusion cc.
Tel: +27 11 673 0411
Mobile: +27 83 294 1876
Email: s.buys at codefusion.co.za

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