Atmos component migration in YAML config

Migrate component from using deprecated key `component` to use `metadata.inherits`

Identify the component to move, we'll use vpc for this example.

Here is an example of the older method of using the component key

# stacks/catalog/vpc.yaml
components:
  terraform:
    vpc:
      # This cannot be enabled here in the older method due to the global
      # AZ fragment importation
      settings:
        spacelift:
          workspace_enabled: false
      vars:
        enabled: true
        # ...etc...

# stacks/gbl-ue2.yaml
components:
  terraform:
    vpc:
      # This is the AZ fragment importation thats imported across all stacks
      # even stacks without a vpc.
      availability_zones:
        - us-east-1a
        - us-east-1b
        - us-east-1c

# stacks/plat-ue2-dev.yaml
import:
  - gbl-ue2
  - catalog/vpc

components:
  terraform:
    vpc:
      component: vpc
      # This is where spacelift has to be enabled
      settings:
        spacelift:
          workspace_enabled: true
      vars:
        name: vpc
        # ...etc...

    vpc1:
      component: vpc
      # This is where spacelift has to be enabled
      settings:
        spacelift:
          workspace_enabled: true
      vars:
        name: vpc1
        # ...etc...

Verify terraform plan for vpc component is a no change. If not, configure it and apply it until it shows no change.
```
⨠ atmos terraform plan vpc --stack plat-ue2-dev
```

Pull down the latest vpc component and repeat the previous step (optional)

⨠ wget https://raw.githubusercontent.com/cloudposse/atmos/master/examples/quick-start/components/terraform/vpc/component.yaml -O components/terraform/vpc/component.yaml
⨠ sed -i 's,infra/vpc-flow-logs-bucket,vpc,g' components/terraform/vpc/component.yaml
⨠ atmos vendor pull -c vpc

Verify the current workspace name

⨠ atmos describe component vpc --stack plat-ue2-dev | grep ^workspace
workspace: plat-ue2-dev

Count the current root stacks where the vpc component is defined

⨠ atmos describe stacks --components=vpc --sections=components | grep -oP '^[a-z0-9-]+' | wc -l
17

In the vpc.yaml stack catalog, rename vpc to be vpc/defaults

Add the metadata block

components:
  terraform:
    vpc/defaults:
      metadata:
        type: abstract
      # spacelift can now be enabled in the catalog
      settings:
        spacelift:
          workspace_enabled: true
      vars:
        enabled: true
        # ...etc...

Create a vpc component that inherits from vpc/defaults

    vpc:
      metadata:
        component: vpc
        inherits:
          - vpc/defaults
      vars:
        name: vpc

Verify the workspace is the same
```
⨠ atmos describe component vpc --stack plat-ue2-dev | grep ^workspace
workspace: plat-ue2-dev
```
NOTE: Since the vpc component name shares the same name as its base component, the workspace will remain the same.

NOTE: If the workspace has the component suffixed to it e.g. plat-ue2-dev-vpc1 then the tfstate will have to be migrated. See component renaming and subsequent tfstate rename below before continuing.
Add availability_zones to vpc/defaults and only add the letters and omit the region.

Move any vpc component global overrides for availability_zones to vpc/defaults.

The vpc configuration may have a fragment in a global region file

    vpc:
      availability_zones:
        - us-east-1a
        - us-east-1b
        - us-east-1c

It can now be set as this in the vpc.yaml catalog

      availability_zones:
        - a
        - b
        - c

Count the root stacks again and verify the number is lower than previous

⨠ atmos describe stacks --components=vpc --sections=components | grep -oP '^[a-z0-9-]+' | wc -l
9

Rerun the plan and verify no changes again

⨠ atmos terraform plan vpc --stack plat-ue2-dev

Renaming components

If renaming a component is desired, for example, from vpc to vpc1, the workspace will change.

Follow these steps to ensure your state is properly managed.

Identify all the stacks affected by the component rename
Select a root stack and the component. We will use plat-ue2-dev root stack and vpc component for this example.
Verify terraform plan for vpc component is a no change. If not, configure and apply it.

Verify the old and new workspaces.

Before renaming

⨠ atmos describe component vpc --stack plat-ue2-dev | grep ^workspace
workspace: plat-ue2-dev

After renaming

⨠ atmos describe component vpc1 --stack plat-ue2-dev | grep ^workspace
workspace: plat-ue2-dev-vpc1

Follow one of the guides below for migrating the state or overriding the workspace
After you have completed the previous step, you will also need to rename any component keys in remote-state.tf files since the original reference to the component has been removed from the tfstate

Migrating state manually

This approach is recommended because this will allow the catalog to be imported without additional overrides.

Navigate to the component and list the workspaces

⨠ cd components/terraform/vpc
⨠ terraform init
⨠ terraform workspace list
default
* plat-gbl-sandbox
  plat-ue2-dev

Select the original component's workspace

⨠ terraform workspace select plat-ue2-dev

Dump the terraform state into a new file

⨠ terraform state pull > plat-ue2-dev.tfstate

Select or create the new workspace if it does not exist

⨠ terraform workspace select plat-ue2-dev-vpc1
⨠ terraform workspace new plat-ue2-dev-vpc1
Created and switched to workspace "plat-ue2-dev-vpc1"!

Push up the original workspace's state to the new workspace's state

⨠ terraform state push plat-ue2-dev.tfstate
Releasing state lock. This may take a few moments...

Verify terraform plan for the new component is a no change.
```
⨠ atmos terraform plan vpc1 --stack plat-ue2-dev
```

Overriding the workspace name

The fastest approach would be to override the workspace name but is not recommended since this will need to be done for every root stack where the catalog is imported.

In the root stack affected, instantiate the component and override the terraform_workspace to match the original.

# root stack: plat-ue2-dev
import:
  - catalog/vpc

components:
  terraform:
    vpc1:
      metadata:
        terraform_workspace: plat-ue2-dev
        component: vpc
        inherits:
          - vpc/defaults
      vars:
        name: vpc

Verify the workspace is correct

⨠ atmos describe component vpc1 --stack plat-ue2-dev | grep ^workspace
workspace: plat-ue2-dev

Repeat the above steps for all the root stacks where the component is imported

Migrate component from using deprecated key component to use metadata.inherits​

Renaming components​

Migrating state manually​

Overriding the workspace name​

Migrate component from using deprecated key `component` to use `metadata.inherits`

Renaming components

Migrating state manually

Overriding the workspace name