Generating Dynamic JSON in Terraform

Bring some movement to your JSON (Image Credit: Ahmad Odeh)

Available for free in English & Portuguese at my personal website.

In this article I’ll use Step Functions as a case study, but you can do it with whatever resources you want.

What we’re going to do

The following JSON will become dynamic. We’ll replace static values with:

1. A variable
2. A dynamic list
3. One or more dynamic objects

(I’ve added non idiomatic comments inside the code blocks, but it’s just to show what exactly we’re doing.)

# Reference JSON
{
    "Comment": "My state machine",
    "StartAt": "Choice",
    "States": {
        "Handle Notification": {
            "Type": "Task",
            "Resource": "arn:aws:states:::lambda:invoke",
            "OutputPath": "$.Payload",
            "Parameters": {
              "Payload.$": "$",
              "FunctionName": "my_function_name"  <-- Case 1: Replace with dynamic string
            },
            "End": true
        },
        "Choice": {
          "Type": "Choice",
          "Choices": [                            ------- 
             {                                           |
               "IsPresent": true,                        |
               "Next": "SSM Execution-InstanceId",       |
               "Variable"…