I have an app which works perfectly on an ubuntu ec2 micro instance, I’ve attempted to get it working on beanstalk and for some reason why I load up the page and the 70+ assets are loading (it’s in dev mode), it ends up crashing half way through. The load balancer seems to automatically transition it to yellow followed by red for a few seconds, then it goes back to green, as soon as it transitions all the assets fail w/ 503 error. When I look at the monitoring all the levels are low, the CPU hardly spikes at all.
What I want to know is how I troubleshoot what is causing the load balancer to start returning 503’s. I’m also wondering how that is even possible, isn’t the idea of beanstalk to allow the app to auto-scale?
I would look at the 503’s closely to see if they are generated by the ELB or the backend instances? This is closely related to the Unhealthyhost count metric on CloudWatch. Following up to that I would recommend revisiting health check config on the load balancer.