Docker links with awsvpc network mode

Question

I have a Java webapp deployed in ECS using the tomcat:8.5-jre8-alpine image. The network mode for this task is awsvpc; I have many of these tasks running across 3 EC2 instances fronted by an ALB.

This is working fine but now I want to add an nginx reverse-proxy in front of each tomcat container, similar to this example: https://github.com/awslabs/ecs-nginx-reverse-proxy/tree/master/reverse-proxy.

My abbreviated container definition file is:

{
    "containerDefinitions": [
     {
       "name": "nginx",
       "image": "<NGINX reverse proxy image URL>",
       "memory": "256",
       "cpu": "256",
       "essential": true,
       "portMappings": [
         {
           "containerPort": "80",
           "protocol": "tcp"
         }
       ],
       "links": [
         "app"
       ]
     },
     {
       "name": "app",
       "image": "<app image URL>",
       "memory": "1024",
       "cpu": "1024",
       "essential": true
     }
    ],
    "volumes": [],
    "networkMode": "awsvpc",
    "placementConstraints": [],
    "family": "application-stack"
}

When I try to save a new task definition I received the error: "links are not supported when the network type is awsvpc"

I am using the awsvpc network mode because it gives me granular control over the inbound traffic via a security group.

Is there any way to create a task definition with 2 linked containers when using awsvpc network mode?

Milan Markovic Milan Markovic · Accepted Answer · 2019-04-03T18:40:55

You dont need the linking part at all, because awsvpc allows you to reference other containers simply by using

localhost:8080 (or whatever port is your other container mapped to)

in your nginx config file.

So remove links from your json and use localhost:{container-port} in nginx config. Simple as that.

Docker links with awsvpc network mode

2 Answers