ECS managed Docker configuration

Dockerrun.aws.json is an Elastic Beanstalk configuration file that describes how to deploy a set of Docker containers hosted in an ECS cluster in an Elastic Beanstalk environment. The Elastic Beanstalk platform creates an ECS task definition, which includes an ECS container definition. These definitions are described in the Dockerrun.aws.json configuration file.

The container definition in the Dockerrun.aws.json file describes the containers to deploy to each Amazon EC2 instance in the ECS cluster. In this case an Amazon EC2 instance is also referred to as a host container instance, because it hosts the Docker containers. The configuration file also describes the data volumes to create on the host container instance for the Docker containers to mount. For more information and a diagram of the components in an ECS managed Docker environment on Elastic Beanstalk, see the ECS managed Docker platform earlier in this chapter.

A Dockerrun.aws.json file can be used on its own or zipped up with additional source code in a single archive. Source code that is archived with a Dockerrun.aws.json is deployed to Amazon EC2 container instances and accessible in the /var/app/current/ directory.

Dockerrun.aws.json v2

The Dockerrun.aws.json file includes the following sections:

AWSEBDockerrunVersion

Specifies the version number as the value 2 for ECS managed Docker environments.

volumes

Creates volumes from folders in the Amazon EC2 container instance, or from your source bundle (deployed to /var/app/current). Mount these volumes to paths within your Docker containers using mountPoints in the containerDefinitions section.

containerDefinitions

An array of container definitions.

authentication (optional)

The location in Amazon S3 of a .dockercfg file that contains authentication data for a private repository.

The containerDefinitions and volumes sections of Dockerrun.aws.json use the same formatting as the corresponding sections of an Amazon ECS task definition file. For more information about the task definition format and a full list of task definition parameters, see Amazon ECS task definitions in the Amazon Elastic Container Service Developer Guide.

Volume format

The volume parameter creates volumes from either folders in the Amazon EC2 container instance, or from your source bundle (deployed to /var/app/current).

Volumes are specified in the following format:

"volumes": [
    {
      "name": "volumename",
      "host": {
        "sourcePath": "/path/on/host/instance"
      }
    }
  ],

Mount these volumes to paths within your Docker containers using mountPoints in the container definition.

Elastic Beanstalk configures additional volumes for logs, one for each container. These should be mounted by your Docker containers in order to write logs to the host instance.

For more details, see the mountPoints field in the Container definition format section that follows.

Container definition format

The following examples show a subset of parameters that are commonly used in the containerDefinitions section. More optional parameters are available.

The Beanstalk platform creates an ECS task definition, which includes an ECS container definition. Beanstalk supports a sub-set of parameters for the ECS container definition. For more information, see Container definitions in the Amazon Elastic Container Service Developer Guide.

A Dockerrun.aws.json file contains an array of one or more container definition objects with the following fields:

name

The name of the container. See Standard Container Definition Parameters for information about the maximum length and allowed characters.

image

The name of a Docker image in an online Docker repository from which you're building a Docker container. Note these conventions:

• Images in official repositories on Docker Hub use a single name (for example, ubuntu or mongo).

• Images in other repositories on Docker Hub are qualified with an organization name (for example, amazon/amazon-ecs-agent.

• Images in other online repositories are qualified further by a domain name (for example, quay.io/assemblyline/ubuntu).

environment

An array of environment variables to pass to the container.

For example, the following entry defines an environment variable with the name Container and the value PHP:

"environment": [
  {
    "name": "Container",
    "value": "PHP"
  }
],

essential

True if the task should stop if the container fails. Nonessential containers can finish or crash without affecting the rest of the containers on the instance.

memory

Amount of memory on the container instance to reserve for the container. Specify a non-zero integer for one or both of the memory or memoryReservation parameters in container definitions.

memoryReservation

The soft limit (in MiB) of memory to reserve for the container. Specify a non-zero integer for one or both of the memory or memoryReservation parameters in container definitions.

mountPoints

Volumes from the Amazon EC2 container instance to mount, and the location on the Docker container file system at which to mount them. When you mount volumes that contain application content, your container can read the data you upload in your source bundle. When you mount log volumes for writing log data, Elastic Beanstalk can gather log data from these volumes.

Elastic Beanstalk creates log volumes on the container instance, one for each Docker container, at /var/log/containers/containername. These volumes are named awseb-logs-containername and should be mounted to the location within the container file structure where logs are written.

For example, the following mount point maps the nginx log location in the container to the Elastic Beanstalk–generated volume for the nginx-proxy container.

{
  "sourceVolume": "awseb-logs-nginx-proxy",
  "containerPath": "/var/log/nginx"
}

portMappings

Maps network ports on the container to ports on the host.

links

List of containers to link to. Linked containers can discover each other and communicate securely.

volumesFrom

Mount all of the volumes from a different container. For example, to mount volumes from a container named web:

"volumesFrom": [
  {
    "sourceContainer": "web"
  }
],

Authentication format – using images from a private repository

The authentication section contains authentication data for a private repository. This entry is optional.

Add the information about the Amazon S3 bucket that contains the authentication file in the authentication parameter of the Dockerrun.aws.json file. Make sure that the authentication parameter contains a valid Amazon S3 bucket and key. The Amazon S3 bucket must be hosted in the same region as the environment that is using it. Elastic Beanstalk will not download files from Amazon S3 buckets hosted in other regions.

Uses the following format:

"authentication": {
    "bucket": "DOC-EXAMPLE-BUCKET",
    "key": "mydockercfg"
  },

For information about generating and uploading the authentication file, see Using images from a private repository in the Environment configuration topic of this chapter.

Example Dockerrun.aws.json v2

The following snippet is an example that illustrates the syntax of the Dockerrun.aws.json file for an instance with two containers.

{
  "AWSEBDockerrunVersion": 2,
  "volumes": [
    {
      "name": "php-app",
      "host": {
        "sourcePath": "/var/app/current/php-app"
      }
    },
    {
      "name": "nginx-proxy-conf",
      "host": {
        "sourcePath": "/var/app/current/proxy/conf.d"
      }
    }
  ],
  "containerDefinitions": [
    {
      "name": "php-app",
      "image": "php:fpm",
      "environment": [
        {
          "name": "Container",
          "value": "PHP"
        }
      ],
      "essential": true,
      "memory": 128,
      "mountPoints": [
        {
          "sourceVolume": "php-app",
          "containerPath": "/var/www/html",
          "readOnly": true
        }
      ]
    },
    {
      "name": "nginx-proxy",
      "image": "nginx",
      "essential": true,
      "memory": 128,
      "portMappings": [
        {
          "hostPort": 80,
          "containerPort": 80
        }
      ],
      "links": [
        "php-app"
      ],
      "mountPoints": [
        {
          "sourceVolume": "php-app",
          "containerPath": "/var/www/html",
          "readOnly": true
        },
        {
          "sourceVolume": "nginx-proxy-conf",
          "containerPath": "/etc/nginx/conf.d",
          "readOnly": true
        },
        {
          "sourceVolume": "awseb-logs-nginx-proxy",
          "containerPath": "/var/log/nginx"
        }
      ]
    }
  ]
}