Retrieving information from a deployed CloudFormation Stack

This example shows how to use get_stack_outputs and get_physical_id_from_stack to retrieve information from a deployed AWS CloudFormation Stack. They are useful if you deploy your stack directly with a CloudFormation template.

System Under Test

We will use SAM CLI to deploy the SUT to CloudFormation. The SUT consists of one SQS Queue. After deploying the SUT, the Queue URL of the queue can be retrieved from both Physical ID and Outputs.

01-cfn_utils/template.json

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "simple SQS template",
    "Resources": {
        "SQSQueue": {
            "Type": "AWS::SQS::Queue"
        }
    },
    "Outputs": {
        "QueueURL": {
            "Description": "URL of newly created SQS Queue",
            "Value": {
                "Ref": "SQSQueue"
            }
        },
        "QueueURLFromGetAtt": {
            "Description": "Queue URL",
            "Value": {
                "Fn::GetAtt": [
                    "SQSQueue",
                    "QueueUrl"
                ]
            }
        },
        "QueueArn": {
            "Description": "Queue ARN",
            "Value": {
                "Fn::GetAtt": [
                    "SQSQueue",
                    "Arn"
                ]
            }
        }
    }
}

To deploy the stack using AWS SAM CLI:

cd "01-cfn_utils"

sam deploy --stack-name example-01 --template ./template.json

Test Code

Python

In the test code, we use both get_stack_outputs and get_physical_id_from_stack to get the Queue URL, then assert the values returned from both methods are equal.

01-cfn_utils/test_example_01.py

import os
import aws_iatk

def test_iatk_utils():
    stack_name = os.getenv("STACK_NAME", "example-01")
    region = os.getenv("AWS_REGION", "us-east-1")
    iatk = aws_iatk.AwsIatk(region=region)

    outputs = iatk.get_stack_outputs(
        stack_name=stack_name,
        output_names=["QueueURL"],
    ).outputs

    physical_id = iatk.get_physical_id_from_stack(
        stack_name=stack_name,
        logical_resource_id="SQSQueue",
    ).physical_id

    assert physical_id == outputs["QueueURL"]

To run the test code:

pytest test_example_01.py

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Last update: 2023-11-09