How to connect multiple Docker containers in AWS ElasticBeanstalk? - amazon-web-services

Question

I have a Docker multicontainer configuration meant to run in a ElasticBeanstalk environment.
The EB environment runs in a VPC, in a public subnet, has a single load-balancer and a single instance bound.
It looks like all of the containers are running fine but they cannot communicate with each other even though i defined them as linked containers.
What do I need to do to get all of these containers talking to each other?
My Dockerrun.aws.json looks like this:
"containerDefinitions":
[
{
"name": "proxy",
"image": "nginx",
"essential": true,
"memory": 128,
"portMappings":
[
{
"hostPort": 80,
"containerPort": 80
}
],
"links":
[
"webapp"
],
"mountPoints":
[
{
"sourceVolume": "nginx-conf",
"containerPath": "/etc/nginx/conf.d",
"readOnly": true
},
{
"sourceVolume": "awseb-logs-proxy",
"containerPath": "/var/log/nginx"
}
]
},
{
"name": "webapp",
"image": "jetty",
"memory": 2048,
"essential": true,
"portMappings":
[
{
"hostPort": 8080,
"containerPort": 8080
}
],
"links":
[
"mongodb"
],
"mountPoints":
[
{
"sourceVolume": "jetty-webapp",
"containerPath": "/var/lib/jetty/webapps",
"readOnly": false
},
{
"sourceVolume": "awseb-logs-webapp",
"containerPath": "/var/log/jetty"
}
]
},
{
"name": "mongodb",
"image": "mongo",
"memory": 1024,
"essential": true,
"portMappings":
[
{
"hostPort": 27017,
"containerPort": 27017
}
],
"mountPoints":
[
{
"sourceVolume": "mongodb-data",
"containerPath": "/data/db",
"readOnly": false
}
]
}
]

Answer 1

In 2017, Use the container definition: links with the name of the Docker container you want to connect to. Docker's built-in network bridge will make the connections from there.

Answer 2

In my case, it had nothing to do with the security groups since all I am exposing publicly is 80 for the Nginx proxy.
It came down to using the names in my /etc/host (webapp, mongodb), instead of the IP, that were created for the containers.
This fixes my connection from Nginx to Jetty and Jetty to MongoDB.