Using parameter override functions with CodePipeline pipelines

In a CodePipeline stage, you can specify parameter overrides for AWS CloudFormation actions. Parameter overrides let you specify template parameter values that override values in a template configuration file. AWS CloudFormation provides functions to help you to specify dynamic values (values that are unknown until the pipeline runs).

Fn::GetArtifactAtt

The Fn::GetArtifactAtt function retrieves the value of an attribute from an input artifact, such as the S3 bucket name where the artifact is stored. Use this function to specify attributes of an artifact, such as its file name or Amazon S3 bucket name.

When you run a pipeline, CodePipeline copies and writes files to the pipeline's artifact store (an S3 bucket). CodePipeline generates the file names in the artifact store. These file names are unknown before you run the pipeline.

For example, in your pipeline, you might have a source stage where CodePipeline copies your AWS Lambda function source code to the artifact store. In the next stage, you have an AWS CloudFormation template that creates the Lambda function, but AWS CloudFormation requires the file name to create the function. You must use the Fn::GetArtifactAtt function to pass the exact S3 bucket and file names.

Syntax

Use the following syntax to retrieve an attribute value of an artifact.

{ "Fn::GetArtifactAtt" : [ "artifactName", "attributeName" ] }

Example

The following parameter overrides specify the BucketName and ObjectKey parameters by retrieving the S3 bucket name and file name of the LambdaFunctionSource artifact. This example assumes that CodePipeline copied Lambda function source code and saved it as an artifact, for example, as part of a source stage.

{
  "BucketName" : { "Fn::GetArtifactAtt" : ["LambdaFunctionSource", "BucketName"]},
  "ObjectKey" : { "Fn::GetArtifactAtt" : ["LambdaFunctionSource", "ObjectKey"]}
}

Attributes

You can retrieve the following attributes for an artifact.

Fn::GetParam

The Fn::GetParam function returns a value from a key-value pair in a JSON-formatted file. The JSON file must be included in an artifact.

Use this function to retrieve output values from an AWS CloudFormation stack and use them as input for another action. For example, if you specify an output file name for an AWS CloudFormation action, CodePipeline saves the output in a JSON file and then adds it to the output artifact's .zip file. Use the Fn::GetParam function to retrieve the output value, and use it as input for another action.

Syntax

Use the following syntax to retrieve a value from a key-value pair.

{ "Fn::GetParam" : [ "artifactName", "JSONFileName", "keyName" ] }

Examples

The following examples demonstrate how to use the Fn::GetParam function in a parameter override.

Syntax

The following parameter override specifies the WebSiteURL parameter by retrieving the value of the URL key from the stack-output.json file that is in the WebStackOutput artifact.

{
  "WebSiteURL" : { "Fn::GetParam" : ["WebStackOutput", "stack-output.json", "URL"]}
}

AWS CloudFormation template snippets

The following AWS CloudFormation template snippets, from a CodePipeline pipeline, demonstrate how to pass stack outputs. These snippets show two stages of pipeline definition. The first stage creates a stack and saves its outputs in the TestOutput.json file in the StackAOutput artifact. These values are specified by the OutputFileName and OutputArtifacts properties.

The name of the source input artifact for the stages is TemplateSource. The file name for the stack template is teststackA.yaml, and the file name for the configuration file is test-configuration.json. In both stages, these values are specified for the TemplateConfiguration and TemplatePath properties as shown:

TemplateConfiguration: TemplateSource::test-configuration.json
TemplatePath: TemplateSource::teststackA.yaml

- Name: CreateTestStackA
  Actions:
    - Name: CloudFormationCreate
      ActionTypeId:
        Category: Deploy
        Owner: AWS
        Provider: CloudFormation
        Version: '1'
      Configuration:
        ActionMode: CREATE_UPDATE
        Capabilities: CAPABILITY_IAM
        OutputFileName: TestOutput.json
        RoleArn: !GetAtt [CFNRole, Arn]
        StackName: StackA
        TemplateConfiguration: TemplateSource::test-configuration.json
        TemplatePath: TemplateSource::teststackA.yaml
      InputArtifacts:
        - Name: TemplateSource
      OutputArtifacts:
        - Name: StackAOutput
      RunOrder: '1'

In a subsequent stage, stack B uses the outputs from stack A. In the ParameterOverrides property, the example uses the Fn::GetParam function to specify the StackBInputParam parameter. The resulting value is the value associated with the StackAOutputName key.

- Name: CreateTestStackB
  Actions:
    - Name: CloudFormationCreate
      ActionTypeId:
        Category: Deploy
        Owner: AWS
        Provider: CloudFormation
        Version: '1'
      Configuration:
        ActionMode: CREATE_UPDATE
        Capabilities: CAPABILITY_IAM
        RoleArn: !GetAtt [CFNRole, Arn]
        StackName: StackB
        TemplateConfiguration: TemplateSource::test-configuration.json
        TemplatePath: TemplateSource::teststackB.yaml
        ParameterOverrides: |
          {
            "StackBInputParam" : { "Fn::GetParam" : ["StackAOutput", "TestOutput.json", "StackAOutputName"]}
          }
      InputArtifacts:
        - Name: TemplateSource
        - Name: StackAOutput
      RunOrder: '1'

See also

The following related resources can help you as you work with these parameters.