Subject: Re: [nfsv4] [FedFS] caching LDAP lookups

From: James Lentini <[email-masked]>
Date: Tue, 2 Jun 2009 11:24:54 -0400 (EDT)

On Fri, 29 May 2009, Paul Lemahieu wrote:

> I spoke briefly with Mario today about the LDAP caching issue, and 
> he echoed our comments about how LDAP directories already see peak 
> load situations first thing in the morning, etc, and he would expect 
> the LDAP infrastructure to handle FedFS lookups.

The performance results you cited in your previous email support his 
expectations. Given the strong performance results, long-term caching 
of FSN-to-FSL mappings (anything more than a few minutes) should not 
be necessary. 

<snip> 
> Mario felt caching was a good idea, and that some basic 
> recommendations and defaults should be made in the FedFS standard to 
> guide those who wish to cache LDAP lookups.

Did he mentioned if there were standard, supported mechanisms to 
assist LDAP clients in caching directory data?

I've discovered RFC 3928 "Lightweight Directory Access Protocol (LDAP) 
Client Update Protocol (LCUP)":

 http://www.ietf.org/rfc/rfc3928.txt

which provides a mechanism for LDAP clients to be notified when a 
directory's contents change. This seems like it would be an ideal way 
to learn when a FSN-to-FSL mapping was updated. Unfortunately, LCUP 
appears to have been abandoned:

 http://blogs.gnome.org/markmc/2006/01/24/ldap-notifications/

and the various LDAP implementations provide different, non-standard 
mechanisms to support this.

-james

---

From: [email-masked]
Date: Tue, 2 Jun 2009 19:05:17 -0400

>> -----Original Message-----
>> From: [email-masked] [mailto:[email-masked]] 
>> On Behalf Of James Lentini
>> Sent: Tuesday, June 02, 2009 11:25 AM
>> To: LeMahieu, Paul
>> Cc: [email-masked]
>> Subject: Re: [nfsv4] [FedFS] caching LDAP lookups
>> 
>> 
>> 
[MW] As far as I know there are no standard specifications for the
caching
 of the results of LDAP queries. Each use case and resulting
implementation
 use the mechanism that better suits their needs

>> mechanisms to support this.

[MW] Right now there is no mechanism for a LDAP server to notify a
client
 of changes. Some implementations of Directory Services, iPlanet for
instance,
 implement a 'modification-time' attribute, which clients can query,
reducing
 the need for frequent complex queries. But, even then, it depends on
the client
 to query the attribute.

>> 
>> -james
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>>