tfdiff

Generate reports for your migration from ClickOps to Terraform.

Features

Output list of unmanaged resources to CSV
CLI reporting with asset breakdown by region and resource type
Multi-region scan support
Support for AWS SSO managed credentials
Resource type exclusion filtering

Installation

This program may be installed by downloading the latest executable from the releases page, moving it into your path, and making it executable. See the example below for Unix-based environments:

wget https://github.com/cosmotek/tfdiff/releases/download/v1.1.0-rc/tfdiff-linux-amd64.zip
unzip tfdiff-linux-amd64.zip
mv tfdiff /usr/local/bin/tfdiff
chmod +x /usr/local/bin/tfdiff

Usage

Before running tfdiff, you will need to have the following:

An AWS account with Resource Explorer 2 enabled
A valid AWS credentials file with a profile for the account you want to diff
Terraform installed on your machine

Once you have all the requirements, you may run tfdiff like so:

# open your terraform project
cd my-terraform-project

# select the terraform workspace you want to diff (assuming you have one)
terraform workspace select development

# select an AWS profile with credentials for the target environment
export AWS_PROFILE=development

# run tfdiff against two regions (instead of defaulting to all regions), outputing the list of unmanaged resources to a csv file
tfdiff aws --regions=us-east-1,us-east-2 --output-file unmanaged_resources.csv

Ignore Files

In order to ignore one or many resources when scanning the system, create a file named .tfdiff_ignore located within the Terraform project directory you've been operating in. Just specify one ARN or glob per a line, save, and run tfdiff. Ignore files are automatically detected and validated before each scan.

Here's a little example:

arn:aws:rds:us-east-1:0123456789:*
arn:aws:ecs:us-east-1:0123456789:*
arn:aws:ecs:us-east-1:0123456789:task-definition/amazing-api:123

For more configuration options, run tfdiff aws --help.

Known issues & limitations

AWS Inventory Truncation: This tool uses the AWS Resource Explorer 2 API to list asset inventory in the target environment. This API has a max page size of 1000, with no pagination support. Tfdiff scans each region and each resource type individually in order avoid to hitting this limit, but it's possible that regions/resource types with many assets may be truncated at 1000. We are currently exploring other workarounds. For now Tfdiff will output a warning for any region/resource type combo that returns exactly 1000 resources.
AWS Service Quotas: Given Tfdiff makes num_target_regions * num_resource_types queries for each diff, the AWS services quotas may be exceeded with many monthly executions. Hitting a quota will cause this tool to error out completely. You may request a quota adjustment by AWS in the Services Quota Console.

Planned features

Resource Type Filters
The ability to ignore resources by ARN/Identifier via .tfdiff_ignore files
Support for GCP, Azure & DigitalOcean
(Possible) Scan Caching
Support for multiple Terraform projects and workspaces at once
Automated config drift detection