Does anyone know of a service that will run a DNS heartbeat check then turn on an ec2 machine and forward all requests to that machine if the original(non-ec2) hosted solution goes down?

If not is there tool I could run on the EC2 install to do something similar?


  • Is this for your business use internally or for customers on the Internet? Because if you're looking for "server A is dead, move entirely to server B" I don't know how this would work, since it could move to server B if your connection dies, not your client's, and you could end up with split brain. If the app is designed to support it you probably would just want to use a form of load balancing or geographic balancing. If it's internal that's a different story. Automating this could be asking for headaches. – Bart Silverstrim Aug 5 '10 at 11:47
  • Plus I think Amazon does do something like geographic balancing, but I'm not sure. You might want to research how reliable their service is before overcompensating for availability of your hosted server, then instead make sure you have a good recovery plan (backups, restoration) if something happens instead of maintaining a heartbeat/fencing solution, depending on how mission critical this application is for you and your business. – Bart Silverstrim Aug 5 '10 at 11:49
  • You might end up introducing a different point of failure if you accidentally automate a switchover to another server when there's not really an availability issue or you'll have some customers who can't access the service because you side went down when the EC2 side is working fine. Defeats the purpose :-) – Bart Silverstrim Aug 5 '10 at 11:50
  • So what would the point of a DNS heartbeat check be in general, if I can't rely on the heartbeat check to represent the clients connection? Apologies for the ignorance but if not heartbeat check how do we reliably detect a site is down and take action? Load balancing is more costly/time-consuming solution(would need to sync data in real-time) which isn't really needed, they just need to be up. – Shane Aug 5 '10 at 12:05
  • You have to consider what it means for the site to be down; is it your connection to it, or is it the actual system that's dead? What happens if you automatically cut over to another server if it was actually a glitch in your router or upstream provider? And it depends on the application. What are the ramifications of having a split brain event? Can you resync data properly? Is this overmanagement for your needs to have this in place instead of a good backup to bring it back up in a timely manner? – Bart Silverstrim Aug 5 '10 at 12:24

This is really more of a programming question than a server admin question. You have an idea of the sort of failover you want to do, but it most likely will require a fair but of custom coding to achieve your end result.

Short answer: You can usually get anything to do anything that you want, it just depends how much time you're willing to invest in it. For this, it would be roll your own.

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