bernd,

thank you for the info.  i think i have a better picture now, but still don't grasp some of the details.

first, i see what you are saying about caching applying to ldap, meta and sql backends.  in reading the man page for slapo-pcache, it states that the proxy cache may be used with any backend but is intended for use with what you specify.  does that mean caching will be ineffective or will not occur?  because i have things like dns zone info and the kerberos database in my DIT, it would be a great benefit to get caching working.  i am not opposed to changing the backend if needed, but dont know what pros and cons are to each backend type.  i simply used hdb to learn with.

next, with the examples you give below, it looks like you build at least one level / layer more than i do with my attempt.  i am not sure what i would need to do to create this structure.  your example creates an ldap backend, adds the overlay to the ldap backend, and adds the cache database to the overlay.  because i have an hdb backend, would i want / need to create a separate ldap backend?  could i use the existing hdb backend?  this is really just for learning right now...

On Wed, Mar 20, 2013 at 2:02 PM, Bernd May <bernd@net.t-labs.tu-berlin.de> wrote:
Hey,


On 19.03.2013 15:17, brendan kearney wrote:
> i no longer have logs around the failure, but the error message indicated
> that the olcDbDirectory could not be found.  the DN dn:
> olcDatabase={2}hdb,cn=config has that specified (olcDbDirectory:
> /var/lib/ldap), but i am missing something about pcache and the backend
> sharing this directive.

AFAIK you are missing a database to store the caching data in. While the
manpages and documentation do make mention of this implicitly, neither
of them states it in an obvious way. Unfortunately even the examples in
the admin guide are a bit misleading because the DNs there do not
reflect the object hierarchy in the config database.
So to solve your problem you will need a second database, that stores
the caching data, e.g.

# your database backend you want to cache for
dn: olcDatabase={2}ldap,cn=config
...
# the pcache overlay
dn: olcOverlay={0}pcache,olcDatabase={2}ldap,cn=config
...
# the pcache overlay db
dn: olcDatabase=hdb,olcOverlay={0}pcache,olcDatabase={2}ldap,cn=config
...
objectClass: olcPcacheDatabase
olcDbDirectory: /var/lib/ldap/pcache
olcDbIndex: pcacheQueryID eq
...

Note also that pcache is meant to increase the performance of ldap and
meta backends. I do not know whether it makes sense or actually works to
cache entries for a mundane hdb database.

hth

--
Technische Universität Berlin - FGINET

Bernd May

System Administration
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