Re: slapd-read hangs (ITS#3832)

[hyc@symas.com]

Aaron Richton wrote:
>> A hanging read wouldn't cause a modification to fail. Look more closely
>> at the output from the failed run and you'll probably see one of the
>> Modify tasks failed with (52) Server Unavailable. I've been getting this
>> occasionally as well on 036 and 039.
>>     
>
> Sure enough, that's it. I've saved up the testrun directory if anybody
> cares to take a look and can't repro on their platform.
I've traced a bit of what's going on in my testrun slapd.?.log files. 
Basically the META_BIND_TIMEOUT is too fast. If a Bind doesn't succeed 
in one or two tries, it gives up. The reason for the slow Binds is that 
slapd.3 receives many Bind requests (one on each of several inbound 
connections) and funnels them all through a pooled connection to 
slapd.1. But slapd only allows maxthreads/2 active operations for any 
given connection, so slapd.1 defers a lot of the incoming operations. 
The test can be "fixed" by doubling the threads setting in slapd.1.conf. 
Or we can change the slapd-* testers to retry when they get an 
LDAP_UNAVAILABLE result.

-- 
  -- 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/