(ITS#6331) slapd freezing, not accepting further 'write' operations while 'read' operations are unaffected

[j@telepaths.org]

Full_Name: Jeff Doyle
Version: 2.4.17
OS: Debian/Lenny
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (130.94.106.251)


Greetings,

Occasionally, I will find one of my servers (running Debian/Lenny with
back-ported slapd version 2.4.17) in a state where the following occurs:

  * Write operations will 'freeze' - leaving the requester at a frozen prompt or
frozen LDAP-client of some kind (from wherever the write-operation originated).
  * slapd refuses to 'stop', even though it indicates that its waiting for "0"
processes to complete.
  * Logs do not indicate a segfault nor any poorly terminated processes.
  * Read operations on same server continue to function normally. Any data that
existed before the "freeze" is returned as it should be.

Modules used:

  * accesslog
  * back_hdb
  * back_monitor
  * back_relay
  * back_rwm
  * syncprov

Servers are all fairly new, and reasonably beefy for their purposes:

  * 6GB RAM
  * 2+ GHz CPU, all QuadCore Xeon and all running amd64 kernel (current with
Lenny)
  * Plenty of Disk Space (gigs and gigs)
  * Servers are SLEEPING (0.00 avg load)

slapd is making use of 'tool-threads' with a value of '4' - however changing
this value has had no effect - Just a side note.

Inform me of any further configs and/or information that you need, and I will
provide it promptly.

Thanks,

Jeff