Implement resource import

8min
|
Terraform

In this tutorial, you will add import capabilities to the order resource of a provider that interacts with the API of a fictional coffee-shop application called Hashicups. To do this, you will:

Implement resource import.
This import method takes the given order ID from the terraform import command and enables Terraform to begin managing the existing order.
Verify import functionality.
This ensures that resource import functionality is working as expected.

Prerequisites

To follow this tutorial, you need:

Go 1.21+ installed and configured.
Terraform v1.8+ installed locally.
Docker and Docker Compose to run an instance of HashiCups locally.

Navigate to your terraform-provider-hashicups directory.

Your code should match the 07-delete-order directory from the example repository.

If you haven't already done so, clone the Terraform HashiCups Provider repository.

$ git clone https://github.com/hashicorp/terraform-provider-hashicups

Change into the 07-delete-order directory of cloned repository.

$ cd terraform-provider-hashicups/07-delete-order

Then, install all the provider's dependencies.

$ go mod tidy

Build the provider

Terraform installs providers and verifies their versions and checksums when you run terraform init. Terraform will download your providers from either the provider registry or a local registry. However, while building your provider you will want to test Terraform configuration against a local development build of the provider. The development build will not have an associated version number or an official set of checksums listed in a provider registry.

Terraform allows you to use local provider builds by setting a dev_overrides block in a configuration file called .terraformrc. This block overrides all other configured installation methods.

Terraform searches for the .terraformrc file in your home directory and applies any configuration settings you set.

First, find the GOBIN path where Go installs your binaries. Your path may vary depending on how your Go environment variables are configured.

$ go env GOBIN
/Users/<Username>/go/bin

If the GOBIN go environment variable is not set, use the default path, /Users/<Username>/go/bin.

Create a new file called .terraformrc in the root directory (~), then add the dev_overrides block below. Change the <PATH> to the value returned from the echo $GOBIN command above.

~/.terraformrc

provider_installation {

  dev_overrides {
    "hashicorp.com/edu/hashicups" = "<PATH>"
  }

  # For all other providers, install them directly from their origin provider
  # registries as normal. If you omit this, Terraform will _only_ use
  # the dev_overrides block, and so no other providers will be available.
  direct {}
}

You must create your CLI configuration file in your user %APPDATA% root directory. The physical location of this directory depends on your Windows version and system configuration.

Search for the user environment variables in PowerShell to find its location on your system.

$ $env:APPDATA

In another terminal, change into the directory returned from the command above.

Find the GOBIN path where go installs your binaries. Your path may vary depending on how your Go environment variables are configured.

$ go env GOBIN
/Users/<Username>/go/bin

If the GOBIN go environment variable is not set, use the default path, /Users/<Username>/go/bin.

Create a new file called terraform.rc and add the dev_overrides block below. Change the <PATH> to the value returned from the go env GOBIN command above.

terraform.rc

provider_installation {

  dev_overrides {
    "hashicorp.com/edu/hashicups" = "<PATH>"
  }

  # For all other providers, install them directly from their origin provider
  # registries as normal. If you omit this, Terraform will _only_ use
  # the dev_overrides block, and so no other providers will be available.
  direct {}
}

Start HashiCups locally

Your HashiCups provider requires a running instance of HashiCups. Navigate to the docker_compose directory.

$ cd docker_compose

Run docker-compose up to spin up a local instance of HashiCups on port 19090.

$ docker-compose up

Leave this process running in your terminal window. The HashiCups service will print out log messages in this terminal.

In the original terminal window, verify that HashiCups is running by sending a request to its health check endpoint. The HashiCups service will respond with ok.

$ curl localhost:19090/health
ok

Create a HashiCups user

HashiCups requires a username and password to generate a JSON web token (JWT) which is used to authenticate against protected endpoints. You will use this user to authenticate to the HashiCups provider to manage your orders.

Create a user on HashiCups named education with the password test123.

$ curl -X POST localhost:19090/signup -d '{"username":"education", "password":"test123"}'
{"UserID":1,"Username":"education","token":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE1OTEwNzgwODUsInVzZXJfaWQiOjIsInVzZXJuYW1lIjoiZWR1Y2F0aW9uIn0.CguceCNILKdjOQ7Gx0u4UAMlOTaH3Dw-fsll2iXDrYU"}

Set the HASHICUPS_TOKEN environment variable to the token you retrieved from invoking the /signup endpoint. You will use this later in the tutorial to verify that Terraform has created your HashiCups order.

$ export HASHICUPS_TOKEN=ey...

The terminal containing your HashiCups logs will record the sign up operation.

api_1  | 2020-12-10T09:19:50.601Z [INFO]  Handle User | signup

Now that the HashiCups app is running, you are ready to start working on the Terraform provider.

If you're stuck at any point during this tutorial, refer to the import-order branch to see the changes implemented in this tutorial.

Implement import functionality

The provider uses the ImportState method to import an existing resource.

The import method implements a single step:

Retrieves import identifier and saves to attribute state. The method will use the resource.ImportStatePassthroughID() function to retrieve the ID value from the terraform import command and save it to the id attribute.

If there are no errors, Terraform will automatically call the resource's Read method to import the rest of the Terraform state. Since the id attribute is all that is necessary for the Read method to work, no additional implementation is required.

Open the internal/provider/order_resource.go file.

Add a new ImportState method to implement importing the resource in order_resource.go with the following.

internal/provider/order_resource.go

func (r *orderResource) ImportState(ctx context.Context, req resource.ImportStateRequest, resp *resource.ImportStateResponse) {
    // Retrieve import ID and save to id attribute
    resource.ImportStatePassthroughID(ctx, path.Root("id"), req, resp)
}

Add the required libraries by replacing the import statement at the beginning of the file with the following.

internal/provider/order_resource.go

import (
    "context"
    "fmt"
    "strconv"
    "time"

    "github.com/hashicorp-demoapp/hashicups-client-go"
    "github.com/hashicorp/terraform-plugin-framework/path"
    "github.com/hashicorp/terraform-plugin-framework/resource"
    "github.com/hashicorp/terraform-plugin-framework/resource/schema"
    "github.com/hashicorp/terraform-plugin-framework/resource/schema/planmodifier"
    "github.com/hashicorp/terraform-plugin-framework/resource/schema/stringplanmodifier"
    "github.com/hashicorp/terraform-plugin-framework/types"
)

Replace the var statement with the following to ensure that your resource implements the ResourceWithImportState interface from the Framework.

internal/provider/order_resource.go

// Ensure the implementation satisfies the expected interfaces.
var (
    _ resource.Resource                = &orderResource{}
    _ resource.ResourceWithConfigure   = &orderResource{}
    _ resource.ResourceWithImportState = &orderResource{}
)

Build and install the updated provider.

$ go install .

Verify import functionality

Navigate to the examples/order directory. This contains a sample Terraform configuration for the Terraform HashiCups provider.

$ cd examples/order

Apply this configuration to ensure that the HashiCups API contains an order.

$ terraform apply -auto-approve
##...
Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

Outputs:

edu_order = {
  "id" = "2"
  "items" = tolist([
    {
##...

Retrieve the order ID from the Terraform state. You will use this order ID to import the order in the next step.

$ terraform show
# hashicups_order.edu:
resource "hashicups_order" "edu" {
    id           = "2"
    items        = [
        # (2 unchanged elements hidden)
    ]
    last_updated = "Wednesday, 14-Dec-22 11:18:20 CST"
}
##...

Remove the existing order from Terraform's state. The order will still exist in the HashiCups API.

$ terraform state rm hashicups_order.edu
Removed hashicups_order.edu
Successfully removed 1 resource instance(s).

Verify that the Terraform state no longer contains the order resource. The previous edu_order output value will still remain.

$ terraform show

Outputs:

edu_order = {
    id           = "2"
    items        = [
##...

Verify that the HashiCups API still has your order. If needed, replace 2 with the order ID from the output of the terraform show command.

$ curl -X GET -H "Authorization: ${HASHICUPS_TOKEN}" localhost:19090/orders/2

Import the existing HashiCups API order into Terraform. Replace the order ID with your order ID.

$ terraform import hashicups_order.edu 2
hashicups_order.edu: Importing from ID "2"...
hashicups_order.edu: Import prepared!
  Prepared hashicups_order for import
hashicups_order.edu: Refreshing state... [id=2]

Import successful!

The resources that were imported are shown above. These resources are now in
your Terraform state and will henceforth be managed by Terraform.

Verify that the Terraform state contains the order again.

$ terraform show
# hashicups_order.edu:
resource "hashicups_order" "edu" {
    id    = "2"
    items = [
        # (2 unchanged elements hidden)
    ]
}

##...

Navigate to the terraform-provider-hashicups directory.

$ cd ../..

Next steps

Congratulations! You have enhanced the order resource with import capabilities.

If you were stuck during this tutorial, checkout the 08-import-order directory in the example repository to see the code implemented in this tutorial.

To learn more about the Terraform Plugin Framework, refer to the Terraform Plugin Framework documentation.
For a full capability comparison between the SDKv2 and the Plugin Framework, refer to the Which SDK Should I Use? documentation.
The example repository contains directories corresponding to each tutorial in this collection.
Submit any Terraform Plugin Framework bug reports or feature requests to the development team in the Terraform Plugin Framework Github repository.
Submit any Terraform Plugin Framework questions in the Terraform Plugin Framework Discuss forum.

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