Elastic BeanStalk MultiContainer docker fails

Question

I want to deploy an multi-container application in elastic beanstalk. I get the following error.

Error 1: The EC2 instances failed to communicate with AWS Elastic Beanstalk, either because of configuration problems with the VPC or a failed EC2 instance. Check your VPC configuration and try launching the environment again.

I have set up the VPC with just the public subnet and the security group that allows all traffic both inbound and outbound. I know this is not encouraged for production level deployment, but I have reduced the complexity to find the cause of the error.

So, the load balancer and the EC2 instance are inside the same public subnet that is attached with the internet gateway. They both share the same security group allowing all the traffic.

Before the above error, I also get another error stating

Error 2: No ecs task definition (or empty definition file) found in environment

Having said, I have bundled my Dockerrun.aws.json file with .ebextensions folder inside the source bundle which the beanstalk uses for deployment. After all these errors, drilling down to two questions:

1. I cannot understand why No ecs task error appears, when I have packaged my dockerrun.aws.json file containing containerDefinitions?
2. Since there is no ecs task running, there is nothing running in the instance. Is this why beanstalk and ELB cannot communicate to the instance? (Assuming my public subnet and all traffic security group is not a problem)

Answer 1

The problem was the VPC. Even I had the simple VPC with just an public subnet, the beanstalk cannot talk to the instance and so cannot deploy the ECS task definition and docker containers in the instance.

By creating two subnets namely public and private and having an NAT instance in public subnet, which becomes the router for the instances in the private subnet. Making the above setup worked for me and I could deploy the ECS task definition successfully to the EC2 instance in the private subnet.