[Dnsmasq-discuss] second dnsmasq machine for "hot standby" - proposals, wanted

Ed W lists at wildgooses.com
Sat Jul 9 21:35:19 BST 2011

Have you thought about looking at keepalived or linux-ha with perhaps
linux virtual servers or some other IP swapping technology?

The basic idea of all high availability stuff is:

- Some decision making to decide who should be master
- Some fencing to ensure that the master is master (all kinds of fun
acronyms here, like STONITH - shoot the other node in the head...)
- IP aliasing or other routing technology to ensure packets flow to the

Obviously you can script all this yourself (which is basically what you
are sketching out in your previous emails).  But it may be worth looking
at some of the well debugged projects so see if they solve any problems

I'm unfortunately not talking from experience, but from a little
knowledge I would suggest you look at keepalived and linux virtual
servers.  The basic idea is that you have a monitoring demon on each
node watching the other (keepalived) and the demon makes various
decisions on who should be master (other node dead, etc).  When you want
to be master you simply add the master IP to your network device and
start answering queries (LVS)...  The master IP basically flip flops
between the nodes according to your rules (what should happen when the
main node goes down, comes up, etc)

For completeness you want some way to fence each node so that simple
cables falling out can't cause wierd issues.  However, you can probably
not worry too much for your requirements

Good luck - please share what you come up with!

Ed W

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