Get all env variables for all AWS Lamda functions in a CloudFormation/SAM stack

get-vars.py

#! /usr/bin/env python

# Use at your own risk and reward.
# requires boto3 to be installed
# example `./get-vars.py MyStack > vars.json`

import sys, json
import boto3
import argparse

parser = argparse.ArgumentParser(
    prog='get-vars',
    description='This function gets environment variable datas from lambda functions in a cloudformation stack'
)

parser.add_argument('--region')
parser.add_argument('--profile', default='default')
parser.add_argument('--stack_name', required=True)
parser.add_argument('--output')
parser.add_argument(
    "--nested", 
    action="store_true",
    help="Check in nested stacks"
)

args = parser.parse_args()

stacks = dict()
merged = dict()
stack_name = args.stack_name
profile = args.profile
output = args.output
nested = args.nested

print(f'Using profile: {profile}')
my_session = boto3.session.Session(profile_name=profile)
if args.region:
    my_session = boto3.session.Session(profile_name=profile, region_name=args.region)
cloudformation_client = my_session.client('cloudformation')
lambda_client = my_session.client('lambda')

# Grab stack from AWS


def list_stack_resources(stack_name):
    global merged
    page = {}

    try:
        stack_resources = cloudformation_client.list_stack_resources(
            StackName=stack_name
        )
    except Exception as e:
        print(e)
        sys.exit()

    print(f"started stack: {stack_name}")
    function_count = 0
    # Grab environment vars from each lambda in the stack
    for resource in stack_resources['StackResourceSummaries']:
        if (resource['ResourceType'] == 'AWS::CloudFormation::Stack') and nested:
            nested_stack = resource.get('PhysicalResourceId').split('/')[1]
            list_stack_resources(nested_stack)

        if (resource['ResourceType'] == 'AWS::Lambda::Function'):
            function_count += 1
            lambda_config = lambda_client.get_function_configuration(
                FunctionName=resource['PhysicalResourceId']
            )
            if 'Environment' in lambda_config and 'Variables' in lambda_config['Environment']:
                page[resource['LogicalResourceId']] = lambda_config['Environment']['Variables']
                merged = {**merged, **lambda_config['Environment']['Variables']}
    print(f"completed stack: {stack_name}")
    print(f"function_count: {function_count}")
    if page != {}:
        stacks[stack_name] = page


list_stack_resources(stack_name)

# print(json.dumps(stacks, indent=2))
print(json.dumps(merged, indent=2))

if output is not None:
    f = open(output, "w")
    f.write(json.dumps({'Parameters': merged}, indent=2))
    f.close()
    print("Write successful")