[Kolab-devel] [issue689] Kolab2 slapd hangs under high loads

[Stephan Buys]

New submission from Stephan Buys <s.buys at codefusion.co.za>:

Under extreme loads slapd just hangs on Kolab2. The sideeffects can be seen               
acutely in /kolab/var/imapd/log/pop3d.log. You will see the server accepting               
connections but never allow any logins. The Web Interface will hang, etc.               
               
Extreme loads mean loads of > 4 (like viewed in top and uptime)               
               
When you stop openldap with /kolab/etc/rc openldap stop the slapd processes               
will not exit and needs to be killed with a SIG_KILL.               
              
There was a thread on kolab-users discussing the issue, to summarise the              
following tuning can be done to improve slapd's performance and reliability.              
The tuning seems to work in production and we are keeping a close eye on it.              
              
1) Create /kolab/var/openldap/openldap-data/DB_CONFIG               
containing:              
set_cachesize   0       26214400        1             
set_tmp_dir /dev/shm             
            
(we used only the top line)            
            
2) Change the following lines     
in /kolab/etc/kolab/templates/slapd.conf.template           
> index   objectClass     eq           
> index   uid             eq           
> index   mail            eq           
> index   alias           eq          
to          
index   objectClass     pres,eq           
index   uid             pres,eq           
index   mail            pres,eq           
index   alias           pres,eq        
     
Add:     
idlcachesize       2000   
      
Run kolabconf, execute slapindex      
  
This adds a presence index, index caching and increases the berkeley DB cache  
size.  
  
Other optimisations we have not tried yet: 
 
1) Increase the number of threads in slapd.conf (default max is 16) 
2) Decrease the idle timeout in slapd.conf

----------
messages: 4096
nosy: martin, steffen, stephanb
priority: critical
status: unread
title: Kolab2 slapd hangs under high loads
topic: server
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