Other Amazon CloudFormation template keys

We've already introduced configuration file keys from Amazon CloudFormation such as Resources, files, and packages. Elastic Beanstalk adds the contents of configurations files to the Amazon CloudFormation template that supports your environment, so you can use other Amazon CloudFormation sections to perform advanced tasks in your configuration files.

Parameters

Parameters are an alternative to Elastic Beanstalk's own custom options that you can use to define values that you use in other places in your configuration files. Like custom options, you can use parameters to gather user configurable values in one place. Unlike custom options, you can not use Elastic Beanstalk's API to set parameter values, and the number of parameters you can define in a template is limited by Amazon CloudFormation.

One reason you might want to use parameters is to make your configuration files double as Amazon CloudFormation templates. If you use parameters instead of custom options, you can use the configuration file to create the same resource in Amazon CloudFormation as its own stack. For example, you could have a configuration file that adds an Amazon EFS file system to your environment for testing, and then use the same file to create an independent file system that isn't tied to your environment's lifecycle for production use.

The following example shows the use of parameters to gather user-configurable values at the top of a configuration file.

Parameters:
  bucket:
    Type: String
    Description: "Name of the Amazon S3 bucket in which to store load balancer logs"
    Default: "DOC-EXAMPLE-BUCKET"
  bucketprefix:
    Type: String
    Description: "Optional prefix. Can't start or end with a /, or contain the word AWSLogs"
    Default: ""

Outputs

You can use an Outputs block to export information about created resources to Amazon CloudFormation. You can then use the Fn::ImportValue function to pull the value into a Amazon CloudFormation template outside of Elastic Beanstalk.

The following example creates an Amazon SNS topic and exports its ARN to Amazon CloudFormation with the name NotificationTopicArn.

Resources:
  NotificationTopic:
    Type: AWS::SNS::Topic

Outputs:
  NotificationTopicArn:
    Description: Notification topic ARN
    Value: { "Ref" : "NotificationTopic" }
    Export:
      Name: NotificationTopicArn

In a configuration file for a different environment, or a Amazon CloudFormation template outside of Elastic Beanstalk, you can use the Fn::ImportValue function to get the exported ARN. This example assigns the exported value to an environment property named TOPIC_ARN.

option_settings:
  aws:elasticbeanstalk:application:environment:
    TOPIC_ARN: '`{ "Fn::ImportValue" : "NotificationTopicArn" }`'

Mappings

You can use a mapping to store key-value pairs organized by namespace. A mapping can help you organize values that you use throughout your configs, or change a parameter value depending on another value. For example, the following configuration sets the value of an account ID parameter based on the current region.

Mappings: 
  Region2ELBAccountId: 
    us-east-1: 
      AccountId: "111122223333"
    us-west-2: 
      AccountId: "444455556666"
    us-west-1: 
      AccountId: "123456789012"
    eu-west-1: 
      AccountId: "777788889999"
...
            Principal: 
              AWS: 
                ? "Fn::FindInMap"
                : 
                  - Region2ELBAccountId
                  - 
                    Ref: "AWS::Region"
                  - AccountId