Terragrunt to Terraform migration. Useful for migrating lots of statefiles down to a single statefile

parse-tfstate.py

#!/usr/bin/env python3
import argparse
import json
import subprocess
from collections import defaultdict

# IE.
# parse-state -o terragrunt.tfstate -n terraform.tfstate -m ec2_bastion

def parse_args():
    parser = argparse.ArgumentParser(description="Tool to move Terraform state resources.")
    parser.add_argument('-a', '--apply', action='store_true', help='Apply changes directly using Terraform.')
    parser.add_argument('-o', '--old_state', default='terragrunt.tfstate', help='Path to the old state file.')
    parser.add_argument('-m', '--module_name', help='Specific module name to target the move operation.')
    parser.add_argument('-n', '--new_state', default='terraform.tfstate', help='Path to the new state file where resources will be moved.')
    return parser.parse_args()

def confirm(prompt):
    while True:
        choice = input(f"{prompt} (y/n): ").lower()
        if choice in ['y', 'n']:
            return choice == 'y'
        print("Invalid input, please enter 'y' or 'n'.")

def load_json_data(file_path):
    try:
        with open(file_path, 'r') as file:
            return json.load(file)
    except (IOError, ValueError) as e:
        print(f"Error reading {file_path}: {e}")
        exit(1)

def extract_resources(data):
    resources = data.get('resources', [])
    resource_dict = defaultdict(list)
    for resource in resources:
        if resource['mode'] != 'data':
            module_prefix = f"{resource['module']}." if 'module' in resource else ""
            for instance in resource.get('instances', []):
                index = instance.get('index_key')
                identifier = f"{module_prefix}{resource['type']}.{resource['name']}"
                if index is not None:
                    formatted_index = f"[{index}]" if isinstance(index, int) else f"[\"{index}\"]"
                    resource_dict[identifier].append(f"{identifier}{formatted_index}")
                else:
                    resource_dict[identifier].append(identifier)

    return [item for sublist in sorted(resource_dict.values(), key=lambda x: x[0]) for item in sublist]

def move_resources(old_state, new_state, resources, module_prefix):
    """Move resources from one state file to another."""
    for resource in resources:
        command = [
            "terraform", "state", "mv",
            "-state", old_state,
            "-state-out", new_state,
            resource, f"{module_prefix}{resource}"
        ]
        result = subprocess.run(command, capture_output=True, text=True)
        if result.returncode != 0:
            print(f"Error moving {resource}: {result.stderr}")
        else:
            print(f"Successfully moved {resource}")

def main():
    args = parse_args()
    data = load_json_data(args.old_state)
    resources = extract_resources(data)
    module_prefix = f"module.{args.module_name}." if args.module_name else ""

    if args.apply:
        if confirm("Are you sure you want to move these resources?"):
            move_resources(args.old_state, args.new_state, resources, module_prefix)
        else:
            print("Operation cancelled.")
    else:
        for resource in resources:
            print(f"terraform state mv -state={args.old_state} -state-out={args.new_state} '{resource}' '{module_prefix}{resource}'")

if __name__ == "__main__":
    main()