How to read a value from a json file in AWS Codepipeline? - aws-lambda

Question

My question: How can Codepipeline read the value of a field in a json file which is in SourceCodeArtifact?
I have Gthub repo that contains a file imageManifest.json which looks like this:
{
"image_id": "docker.pkg.github.com/my-org/my-repo/my-app",
"image_version": "1.0.1"
}
I want my AWS Codepipeline Source stage to be able to read the value of image_version from imageManifest.json and pass it as a parameter to a CloudFormation action in a subsequent stage of my pipeline.
For reference, here is my source stage.
Stages:
- Name: GitHubSource
Actions:
- Name: SourceAction
ActionTypeId:
Category: Source
Owner: ThirdParty
Version: '1'
Provider: GitHub
OutputArtifacts:
- Name: SourceCodeArtifact
Configuration:
Owner: !Ref GitHubOwner
Repo: !Ref GitHubRepo
OAuthToken: !Ref GitHubAuthToken
And here is my deploy stage:
- Name: DevQA
Actions:
- Name: DeployInfrastructure
InputArtifacts:
- Name: SourceCodeArtifact
ActionTypeId:
Category: Deploy
Owner: AWS
Provider: CloudFormation
Version: '1'
Configuration:
StackName: !Ref AppName
Capabilities: CAPABILITY_NAMED_IAM
RoleArn: !GetAtt [CloudFormationRole, Arn]
ParameterOverrides: !Sub '{"ImageId": "${image_version??}"}'
Note that image_version in the last line above is just my aspirational placeholder to illustrate how I hope to use the image_version json value.
How can Codepipeline read the value of a field in a json file which is in SourceCodeArtifact?
StepFunctions? Lambda? CodeBuild?

Answer 1

You can use a CodeBuild step in between Source and Deploy stages.
In CodeBuild step, read the image_version from SourceArtifact (artifact produced by soruce stage) and write to an artifact 'Template configuration' file 1 which is a configuration property of the CloudFormation action. This file can hold parameter values for your CloudFormation stack. Use this file instead of ParameterOverrides you are currently using.

Answer 2

Fn::GetParam is what you want. It can returns a value from a key-value pair in a JSON-formatted file. And the JSON file must be included in an artifact.
Here is the documentation and it gives you some examples: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/continuous-delivery-codepipeline-parameter-override-functions.html#w2ab1c13c20b9
It should be something like:
ParameterOverrides: |
{
"ImageId" : { "Fn::GetParam" : ["SourceCodeArtifact", "imageManifest.json", "image_id"]}
}