What postgres connection string on AWS docker multicontainer app?

Question

What Postgres connection string should I use if I run a docker multicontainer app via Dockerrun.aws.js on AWS ?

I have a Node.JS/Postgres/docker web-application. Postgres runs in its own container and so does the app. Locally, the app runs ok. When I deploy it to AWS via ECR and BeanStalk , the application successfully deploys and runs, but the web-app doesn't connect to Postgres.

In docker-compose.yaml , the host in the connection string is the name of the container (in my case it would be db ). That doesn't work with AWS . Neither does localhost or 127.0.0.1 .

Here is my Dockerrun.aws.js :

{
  "AWSEBDockerrunVersion": 2,
  "volumes": [
    {
      "name": "db-data",
      "host": {
        "sourcePath": "/data/db"
      }
    }
  ],
  "containerDefinitions": [
    {
      "name": "db",
      "image": "db_image_name",
      "essential": true,
      "memory": 128,
      "environment": [
        {
          "name": "POSTGRES_USER",
          "value": "postgres"
        },
        {
          "name": "POSTGRES_PASSWORD",
          "value": "password"
        },
        {
          "name": "PGDATA",
          "value": "/data/db/pgdata"
        }
      ],
      "portMappings": [
        {
          "hostPort": 5432,
          "containerPort": 5432
        }
      ],
      "mountPoints": [
        {
          "sourceVolume": "db-data",
          "containerPath": "/data/db"
        }
      ]
    },
    {
      "name": "app",
      "image": "app_image_name",
      "essential": true,
      "memory": 128,
      "environment": [
        {
          "name": "NODE_ENV",
          "value": "production"
        },
        {
          "name": "DB_HOST",
          "value": "db"
        },
        {
          "name": "DB_PORT",
          "value": "5432"
        },
        {
          "name": "DB_PASSWORD",
          "value": "password"
        }
      ],
      "links": [
        "db"
      ],
      "portMappings": [
        {
          "hostPort": 80,
          "containerPort": 3000
        }
      ]
    }
  ]
}

What should I put in the environment variable DB_HOST ? ( DB_HOST together with DB_PORT are used by the app to construct the connection string.) Thanks a lot.

Answer 1

Beanstalk and Dockerrun.aws.json format offer you a possibility to link containers from the same definition file with the following syntax:

"links": ["some-name"]

In your case you can add a link to "db" and postgres will be available in your app container under db . You don't even need to map container ports if you don't want to expose your postgres container to the world.

You can see an example in use in following docs: https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/create_deploy_docker_v2config.html#create_deploy_docker_v2config_dockerrun