StackOverflow2013

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copied!<p>I understand exactly where you're coming from, my company is in the same position. We care about having a highly available fault tolerant system however the overhead cost simply isn't viable for the traffic we get.</p> <ol> <li>One problem I have with your solution is that you're assuming the micro instance and load balancer wont both die at the same time. With my experience with amazon I can tell you it's defiantly possible that this could happen, however unlikely, its possible that whatever causes your load balancer to die also takes down the micro instance. </li> <li>Another potential problem is you also assume that you will always be able to start another replacement instance during downtime. This is simply not the case, take for example an outage amazon had in their us-east-1 region a few days ago. A power outage caused one of their zones to loose power. When they restored power and began to recover the instances their API's were not working properly because of the sheer load. During this time it took almost 1 hour before they were available. If an outage like this knocks out your load balancer and you're unable to start another you'll be down.</li> </ol> <p>That being said. I find the ELB's provided by amazon are a better solution for me. I'm not sure what the reasoning is behind using HAProxy but I recommend investigating the ELB's as they will allow you to do things such as auto-scaling etc. </p> <p>For each ELB you create amazon creates one load balancer in each zone that has an instance registered. These are still vulnerable to certain problems during severe outages at amazon like the one described above. For example during this downtime I could not add new instances to the load balancers but my current instances ( the ones not affected by the power outage ) were still serving requests.</p> <p>UPDATE 2013-09-30</p> <p>Recently we've changed our infrastructure to use a combination of ELB and HAProxy. I find that ELB gives the best availability but the fact that it uses DNS load balancing doesn't work well for my application. So our setup is ELB in front of a 2 node HAProxy cluster. Using this tool <a href="https://github.com/SBRDevelopment/HAProxyCloud" rel="nofollow" title="HAProxyCloud">HAProxyCloud</a> I created for AWS I can easily add auto scaling groups to the HAProxy servers. </p>

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