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AWS Documentation » AWS Elastic Beanstalk » Developer Guide » Deploying Elastic Beanstalk Applications from Docker Containers » Multicontainer Docker Environments » Multicontainer Docker Configuration

Multicontainer Docker Configuration

A Dockerrun.aws.json file is an Elastic Beanstalk–specific JSON file that describes how to deploy a set of Docker containers as an Elastic Beanstalk application. You can use a Dockerrun.aws.json file for a multicontainer Docker environment.

Dockerrun.aws.json describes the containers to deploy to each container instance (Amazon EC2 instance that hosts Docker containers) in the environment as well as the data volumes to create on the host instance for the containers to mount.

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. Use the volumes section of the config to provide file volumes for the Docker containers running on the host instance. Use the mountPoints section of the embedded container definitions to map these volumes to mount points that applications on the Docker containers can use.

Dockerrun.aws.json v2

The Dockerrun.aws.json file includes three sections:

AWSEBDockerrunVersion

Specifies the version number as the value "2" for multicontainer Docker environments.

containerDefinitions

An array of container definitions, detailed below.

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 container definition.

Note

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. See Container Definition Format for details.

Volumes are specified in the following format: 

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

(optional) The location in Amazon S3 of a .dockercfg file that contains authentication data for a private repository. Uses the following format: 

"authentication": {
    "bucket": "my-bucket",
    "key": "mydockercfg"
  },

See Using Images from a Private Repository for details.

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"
        }
      ]
    }
  ]
}

Using Images from a Private Repository

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.

For information about generating and uploading the authentication file, see Using Images From a Private Repository.

Container Definition Format

The container definition and volumes sections of Dockerrun.aws.json use the same formatting as the corresponding sections of an Amazon ECS task definition file.

The following examples show a subset of parameters that are commonly used. More optional parameters are available. For more information on the task definition format and a full list of task definition parameters, see Amazon ECS Task Definitions in the Amazon ECS 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"
  }
],