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Re: load balancer
On Fri, Aug 28, 2015 at 02:38:33PM +0800, Eileen(=^ω^=) wrote:
> I have two LDAP servers using mirrormode. I want to run a FREE service to
> achieve load balancer for these servers.
> Due to i can't find any load balancer information in OpenLDAP-Admin-Guide,
> so my question is which kind of service do you advice for load balancer, or
> which kind service openldap supported?
Depending on exactly what you want to achieve, you may not need to run
a separate service at all.
Much LDAP client software allows you to specify multiple servers,
which will be tried in rotation until one answers. This gives protection
against unreachable servers.
Another option is to put several 'A' or 'AAAA' records in the DNS entry
for your LDAP service (use a service-specific name like ldap.example.org
rather than the name of the server). Most DNS servers will change the order
of records in each reply (round-robin DNS) so your clients are likely
to spread their load across all servers and will fall back to a different
server if the first attempt does not connect.
The solutions above involve TCP timeouts if servers go down,
and this may be too slow for you. One way to get around that is to use
a service-specific IP address which is shared by two or more servers.
Each server monitors the other and will take over the service address
if necessary. Note that this does not give you load balancing between
the servers: it is a hot-standby system.
If you do not trust the client software to work properly with multiple
server addresses then you could use OpenLDAP with the LDAP back-end
or the META back-end. Both allow you to specify multiple servers and will
handle fallback even if clients don't. This configuration has a very low
resource requirement so you can run an instance of it on every client
machine if you need to.
Andrew
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| From Andrew Findlay, Skills 1st Ltd |
| Consultant in large-scale systems, networks, and directory services |
| http://www.skills-1st.co.uk/ +44 1628 782565 |
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