How to make two containers connectable in AWS ECS Fargate?

Question

I have two containers added to a task definition

1. Node Container:

   name :nodeAPI
   port :exposed 5001
   mongoconnection string in the env variable : mongodb://mongo  [name of mongo container]
   

2. Mongo container:

   name :mongo
   port :exposed 27017
   

The node container is not able to connect to Mongo when I run this task. I am using Fargate and network as awsvpc.

1. How do I fix this?
2. How do I make it work running them from separate task definitions?

Answer 1

there's a security-group configuration when you running the task check whether those are open

fargate security groep

fargate acts like a ec2 onlything is you can use a docker image so you have to do normal ec2 configs

Answer 2

If both containers are defined within the same "Task Definition" than they are able to communicate using "localhost".

In your example your NodeJs app will talk with mongo localhost:27017

Answer 3

As every task in Fargate gets it own ENI, therefore correct way to communicate between containers in same task definition is calling local loopback 127.0.0.1 or localhost.

For example:

First Container will be able to communicate to second container using 127.0.0.1:<port of second container> as address and second container can communicate to First container using 127.0.0.1:<port of first container>

This is very well explained in AWS Blog: https://aws.amazon.com/blogs/compute/task-networking-in-aws-fargate/