[Fedora-directory-users] How to make application connect to multi-master set-up?

[Les Mikesell]

Ankur Agarwal wrote:
>    
> We have a weblogic app server based application which talks to RedHat LDAP through weblogic's security provider APIs.
>    
> On Production env we have set-up master-master LDAP servers i.e. there are two master LDAP servers. How should i make my application connect to these 2 servers?
>    
> Should there be a front-end load balancer to which my application will make request and then load balancer will handle requests to one of the LDAP servers?
>    
> Also note that we have weblogic cluster in Prod with 2 instances. So should i make each instance point to one LDAP server? But in that case how will automatic failover work if one of the LDAP servers go down?
>    
> Would be great if people can suggest any standard solution to deal with such situations. 
> 

If you have multiple A records for the name in DNS, the client will 
receive all of them in a query and _can_ fail over quickly if the first 
choice does not respond.  A lot of web browsers handle this sensibly but 
  most other programs don't.  The way to test it is to set up a DNS 
entry that contains one address that answers on the application's port 
and one that doesn't and see if the application works every time.  If 
you are writing your own client you can get failover a lot cheaper than 
using a dedicated load balancer - and this approach also handles 
connection failures between the client and one of the servers that a 
load balancer would not know about.

-- 
   Les Mikesell
    lesmikesell at gmail.com