Layerform is not actively maintained anymore. Ergomake is now Briefer.

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Layerform

Layerform helps engineers create reusable environment stacks using plain `.tf` files.

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After HashiCorp's announcement that they're not using the MPL license anymore, we'll be building on top of OpenTF.

What is Layerform?

Layerform is a Terraform wrapper that helps engineers build reusable infrastructure using plain Terraform files.

To enable reuse, Layerform introduces the concept of layers. Each layer contains some infrastructure and can be stacked up on top of another layer.

In addition to being much easier to use, Layerform allows teams to reuse core-pieces of infrastructure. That way, development infrastructure is much cheaper and quicker to spin up. With Layerform, Engineers only spawn the infrastructure layers they need.

For those wanting development environments: we don't want to run your text-editor. Layerform is the standard tool for development infrastructure. You can keep using your text-editors, IDEs, and other local development directly on your machine.

Why use Layerform

Cheaper and quicker development infrastructure

Layerform is much cheaper and quicker than spinning up an entire staging environment for each engineer.

When using Layerform, engineers can share the same core-pieces of infrastructure, and only spin up the layers they need on top of it.

For example, if you run applications in a Kubernetes cluster, you don't have to create a brand new cluster for each engineer's environment. Instead, you can reuse the same cluster and have multiple engineers spin up their applications on top of it.

It's just like production, every time

Layerform's environments are just like production because they are spun up from plain .tf files.

Whatever you can set up using a .tf file, you can set up in a Layerform layer.

That way, your development infrastructure will be just like production, including Lambdas, DynamoDB instances, and whatever else that you need.

You own the infrastructure and permissions

Layerform runs in your infrastructure. Layerform will store state and spin up resources in your cloud providers. Therefore, you have full control over who gets access to what, and what resources are currently running, and how much they cost.

Encapsulation / Isolation of concerns

By breaking infrastructure into layers, your organization can define clearer boundaries between teams. Consequently, it will be easier to mirror your organization's structure into your system's structure.

Cost attribution and cost savings

In addition to saving costs by reusing infrastructure, Layerform allows you to automatically track costs for each layer instance.

When applying layers, Layerform will automatically tag the resources it creates with the actual name assigned to the layer instance. If you have production and development base layers, for example, each of those two will contain the tags layerform_layer_name and layerform_layer_instance with their respective names.

That way, Layerform can recursively traverse layers' resources to collect cost management information. Consequently, it will be able to tell the cost of your whole production and development layers, as well as an aggregate cost report of everything on top of those layers.

Getting started

First, install the Layerform CLI.

$ go install github.com/ergomake/layerform@latest

Then, create the Terraform files you'll use to create each layer of infrastructure. In the example below, we have two layers: eks, which is the "base" layer, and services.

layerform/
├─ services/
│ ├─ pods.tf
│ ├─ outputs.tf
│ └─ inputs.tf
├─ eks/
│ ├─ eks.tf
│ ├─ vpc.tf
│ ├─ inputs.tf
│ └─ outputs.tf
├─ services.tf
└─ eks.tf

Once you have your infrastructure defined as code, you'll create the layer definitions that the CLI will use when spawning instances of each layer.

{
    "layers": [
        {
            "name": "base",
            "files": ["./layerform/eks.tf", "./layerform/eks/**"]
        },
        {
            "name": "services",
            "files": ["./layerform/services.tf", "./layerform/services/**"],
            "dependencies": ["base"]
        }
    ]
}

Now, configure the place in which the generated layer definitions will be saved.

# In config inside ~/.layerform
currentContext: remote-context
contexts:
    remote-context:
        type: s3
        bucket: layerform-bucket-example

Finally, you should provision S3 with your layer definitions using layerform configure.

The Layerform CLI will then take care of creating unique IDs for each layer and sending the Terraform files' contents to the Layerform back-end, which, in this case, is an S3 bucket.

After provisioning layer definitions, you can use layerform spawn <definition_name> <desired_id> to create an instance of that particular layer.

$ layerform spawn services my-dev-infra

Each instance of a layer contains all the pieces of infrastructure defined within that layer's files.

In this example, running that command will cause Layerform to also create an instance of the underlying eks layer and assign it the ID default.

To spawn yet another services layer, just run layerform spawn services another-dev-infra. By default, Layerform will try to use underlying layers whose ID is default as base layers.

As a general rule, underlying layers are always the ones whose ID is default. To specify the desired ID for each underlying layer, you'll have to use the --base parameter. For example:

# Creates:
# 1. An eks layer with ID "one"
# 2. A services layer with ID "two"

$ layerform spawn services two --base "eks=one"

Layer immutability and layer rebasing

A layer can only mutate itself or the layers above. For example, if you have a base layer and a backend layer, the backend layer's Terraform files will not be able to mutate any infrastructure in a base layer instance. Still, the base layer files can mutate any instances of the layers above it.

The way Layerform prevents undesirable mutations is by analyzing each terraform plan and detecting whether any mutation's target belongs to an underlying layer.

The reason Layerform prevents a layer from mutating its underlying layer is to avoid breaking sibling pieces of infrastructure.

This design allows for platform teams to "rebase" layer instances on top of theirs. For example, assume you have multiple application layers on top of a Kubernetes cluster belonging to a base layer. In that case, if the platform team wants to update the Kubernetes version and needs to patch existing application's manifests, they can do so from their own layer by referencing and patching other Terraform resources.

On the other hand, product engineers on the layers above cannot modify the base layer containing the Kubernetes cluster. Otherwise, they could break everyone else's applications.

In addition to preventing failures, immutability defines clearer communication interfaces between teams and helps organizations avoid lots of lateral channels.

How Layerform works

Layerform has two major components. The Layerform Back-end, and Layerform CLI.

The Layerform CLI is used to provision the Layerform Back-end with all the metadata for each layer, like its name and dependencies, and all the Terraform files associated with that layer.

The Layerform Back-end stores the data for each layer definition and stores the state for each instance of each layer so that new layers know which base state to use.

There can be multiple types of back-ends. The most common types of back-end are local, for storing data locally, and s3, for storing data on the cloud, in an S3 bucket.

Finally, the Layerform CLI also talks to the Layerform Back-end to fetch the files for the layer it wants to apply, and the state for the underlying layer.

The way the Layerform CLI creates new layers on top of the correct existing layers is by injecting the underlying layer's state when applying each layer.

Layerform design philosophy

Our main goal with Layerform was to make it as easy as possible for engineers to create and share different parts of their infrastructure. That way, we'd empower teams to create their own environments without burdening their organization with unnecessary costs or complex configuration files.

When developing Layerform, we also determined it should support virtually any type of infrastructure, including infrastructure for serverless applications. That's why we decided to create a wrapper on top of a community fork of Terraform, which supports Kubernetes/Helm, and already has established providers for all major public clouds.

Third, we decided Layerform should be simple and intuitive. Engineers shouldn't have to learn new proprietary languages or configuration formats to use Layerform. Whenever possible, we should allow them to reuse their existing configurations. Layerform concepts are the only thing engineers will need to learn about. Everything else should be "just Terraform".

Finally, we decided Layerform needs to be open and free. It's for that reason we're using a GPL license for the wrapper and using a community-maintained fork. That's also why you don't necessarily need to pay for anything before you can extract value from Layerform.

For the sake of transparency, the way we intend to make money in the future is by providing a managed service with governance, management, and cost-control features.

If you wish to bundle the Layerform wrapper itself, the GPL license will take care of ensuring ourselves and the community gets value back.

Usage telemetry

As of 22nd of August, 2023, we've introduced telemetry to the CLI so we can understand how engineers are using the product and improve it accordingly.

To disable telemetry, set the LF_TELEMETRY_DISABLED environment variable to 1.

Issues & Support

You can find Layerform's users and maintainers in GitHub Discussions. There you can ask how to set up Layerform, ask us about the roadmap, and discuss any other related topics.

You can also reach us directly (and more quickly) on our Discord server.

Other channels

• Issue Tracker
• Twitter
• LinkedIn
• Ergomake Engineering Blog

License

Layerform is open-source.

Licensed under the GNU GPLv3 License.

Layerform is not associated with Terraform. Terraform is a registered trademark of HashiCorp, Inc.