I want to set up openldap servers to be available all the time.

Don't we all.

I looked at Master-Slave with Syncrepl and Multi-master configurations. I don't understand which configuration could help me.

Master-Slave means that you have one master that will handle writes, and arbitrary n slaves that will handle reads. Multimaster means that you have an arbitrary n masters that will handle writes, and arbitrary n slaves that will handle reads. It depends on your particular requirements which one you go with; the benefits and drawbacks of both have been discussed at length on this list, so go through the archives.

Also, how would I test my requirement?

A simple method would be to set up a testbed with the desired configuration, and use clients such as OpenLDAP's ldapsearch and ldapmodify to generate load. A simple method to simulate failure is pulling the Ethernet cable (then try running those same clients to make sure things converged nicely).

Is it possible to set up highly available openLDAP servers? Please suggest.

I seriously can't remember the last time I turned off all my slaves. It has probably never happened. I'm not even sure that I took a visible downtime when I went 2.2 -> 2.3. I can't see why I would for 2.3 -> 2.4.

(Not that my machines don't die or anything like that. But they're load balanced, so I don't need to panic when they do.)

On Tuesday 12 February 2008 09:28:12 Ishklight wrote:

Hi,

I want to set up openldap servers to be available all the time.

What aspect needs to be available all the time? Reads, or writes?

If reads need to be available all the time, make sure you have sufficient slaves (taking into account network topology).

If you need HA for writes, then you either need to go with multi-master (you may still need some cluster middleware or load-balancer to ensure that clients always get to a live server), or you need to go with an HA cluster with some kind of shared storage.

Also, how would I test my requirement?

Once you have a technical requirement (and not just a wish), it should be easy to write and implement a test case. In short, this is your job, I'm not going to do it for you (unless you pay me). I doubt others on this list will either.

Is it possible to set up highly available openLDAP servers?

Yes, for over two years I have been running an OpenLDAP 2.3 HA cluster, with (according to our monitoring system) 100% availability.

(I note that the two slaves in that deployment have availability of 100% and 99.99% ...).

Regards, Buchan