Simple HA/HP clustering Using Only DNS

holviala writes "I cooked up a way to achieve high-availability and high-performance clustering using nothing but a few strangely configured dns zones. In case someone else is interested in an extremely easy clustering solution, I wrote a document about it. It's a bit technical, but the included examples should make it clear for anyone who's used to configuring dns. And yes, the linked site is clustered too, so... ummm... no need to be gentle :-)."

Comments

well, not really HA, is it?

[passthecrackpipe]

This only guarantees DNS HA, since it will not test for apache being alive, or any other service being alive. More of a round robin type of setup, with automatic drop of dead addresses. Although it is a nice DNS experiment, I would never use this for HA, as there are better, and - critically - more reliable ways of doing HA, and some of those are pretty affordable.

Face it, you do HA if your business depends on it, and would you really want to rely on a DNS hack in that case?

Having said that - Cool Hack Dude!

Re:well, not really HA, is it?

[holviala]

This only guarantees DNS HA, since it will not test for apache being alive, or any other service being alive.

True, which is why I called it "simple". But with this setup you only need to monitor local processes and services, and if those die only shut down the nameserver. No need for complicated setups where you need to decide if it was the application of the network that died.

Face it, you do HA if your business depends on it, and would you really want to rely on a DNS hack in that case?

My business, yes, I'd rely on this. I do "offical" HA for living for customers who don't like hacks like this. But that's something I'd personally never use, not even if I'd own a million billion zillion dollar company.

Then again, I suffer from the Not Invented Here -syndrome. Guess I'd make a bad leader: "You'll use my DNS hack or you're fired!" :-)

One comment

[tdemark]

Don't use "Domain.dom". There are well-known domains that are reserved explicitly for this purpose.

DNS caching?

[Anonymous Coward]

What about client programs that cache DNS lookups (I think some web browsers do this)? I'd hardly call something HA if I have to do something clientside to flush any cached lookups.

Quite clever

[realnowhereman]

Regardless of what the nit-pickers say, I think this is quite a clever idea. The author isn't suggesting this is the best HA solution in the world; but it's certainly simple and effective.

Re:What's complex about Heartbeat/Ldirectord

[phaze3000]

As someone who maintains two clusters that run LVS, I'd agree that there's nothing that magical about setting it up. However, for a simple two node cluster LVS is a massive overkill - you've got to have as many director boxes as you have nodes!

I'm not sure I'd use this guy's method, but it's interesting nonetheless.