AWS Load Balancer: 503 (Service Unavailable: Back-end server is at capacity)

Question

I setup a load balancer that is forwarding https (443) to https (443) on a simple EC2 nano with AMI Linux using a SSL cert from AWS. After some hours/days by opening the website over https I get a:

Failed to load resource: the server responded with a status of 503 (Service Unavailable: Back-end server is at capacity)

It is redirecting all requests on port 80 to 443 using the .htaccess file.

That is really really annoying. What is wrong in my configuration?

Solution 1

OK. The t2.nano just did not have enough power to run that wordpress site. Now I scaled up and it works without any issues.

Solution 2

For me it happen for another reason - i had no response for root path, e.g. www.myenv.us-east-1.elasticbeanstalk.com, i did had for other path (/someapi/x). But apparently the Load Balancer check the root response and if it's not 200 it will return this 503, which is a bit confusing..

Edit: Another option is to change the Application Health Check path in the configurations