Hi,

I gathered an interesting experience lately with load balancers and LDAP. I
don't remember even the name of the product, but the problem are of general
type.

1. All load balancers support LDAP, No one knows it. 
2. They are designed for the short living connections of http, and not
really apted to manage long living connections as for LDAP
3. They sacrifice a lot of ressources to manage "persistence", adressing
request coming from the same client to the same server

That means that you can implement the redudancy only as a system solution,
not only just putting a load balancer. If the clients don't follow the
rules, you won't achieve that

1. make sure that the clients which use very long sessions are capable to
check the status of a connection and restart it, if it fails (the
programmers have implemented a pool for the LDAP connections, if a
connections fails, they start again all the configured connections)
2. make sure that a client retries a connection after the first failure: it
should try at least three times in intervals of say 15 seconds
3. force the use of LDAPv3 and the automatica supoprt of referrals: this is
extremely useful it you have to maintain the server while providing service
4. You you can afford it, define 2 network interfaces for every server: one
to deliver service the other for replication and internal use. If you have
to withdraw a server for whatever reason, you can still do work with it.

After using the above configuration for about 6 Months, we added LDAP
Proxies, because some of the oldest clients could implement the above points
(connectors).
We use now a redudant configuration of load balancers, a redudant
configuration of LDAP-Proxies and an every increasing number of LDAP Server
(operations rates are in the range of hundredrs per second, growing 250% per
year in the last 3 years).
Every serve has separate interfaces to deliver service and for maintenance,
replication.
Expensive, but needed to deliver 24X7.

Regards
Giovanni




mit freundlichen Grüßen

Giovanni Baruzzi
[EMAIL PROTECTED]

-----Ursprüngliche Nachricht-----
Von: qazmlp [mailto:[EMAIL PROTECTED] 
Gesendet: Donnerstag, 12. Oktober 2006 18:07
An: [email protected]
Betreff: [ldap] Load balancers for LDAP connections??

We normally have 10-15 number of LDAP servers running as the Backend
servers. There are multiple applications connecting to it as LDAP clients.
Hence, I would like to setup a Load balancer especially made up for load
sharing the LDAP connections from the LDAP clients.
Could you give some recommendations on the popularly used LDAP load
balancers?

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