Resources

Note: The Plugin Framework is in beta.

Resources are an abstraction that allow Terraform to manage infrastructure objects by defining create, read, update, and delete functionality that maps onto API operations. Resource schemas define what fields a resource has, give Terraform metadata about those fields, and define how the resource behaves. Refer to Resources in the Framework documentation for details.

This page explains how to migrate a resource's schema from SDKv2 to the plugin Framework. We also recommend reviewing these additional guides for resources throughout the migration:

Create, Read, Update, and Delete functions: The resource defines the logic to manage resources with Terraform.
Import: The resource defines the logic to add a resource to Terraform's state.
Plan modification: The resource customizes the Terraform plan for known values or behaviors outside the practitioner's configuration.
State upgrade: The resource updates Terraform state information in advanced use cases.
Timeouts: The resource uses timeouts during create, read, update or delete operations.

SDKv2

In SDKv2, resources are defined by the ResourcesMap field in the schema.Provider struct, which maps resource names (strings) to their schema. Each schema is a schema.Resource struct that includes:

A Schema field, which defines resource attributes
Fields for resource lifecycle functions such as Create and CreateContext
Fields for functions to implement state upgrade (StateUpgraders), import (Importer), and customize diff (CustomizeDiff)

The following code shows a basic implementation of resource schema with SDKv2.

func New() *schema.Provider {
    return &schema.Provider{
        ResourcesMap:   map[string]*schema.Resource {
            "resource_example": resourceExample(),
            /* ... */
        },
        /* ... */
    }
}

SDKv2 defines the schema.Resource struct as follows.

schema.Resource{
    Schema             map[string]*Schema
    SchemaVersion            int
    MigrateState             StateMigrateFunc
    StateUpgraders           []StateUpgrader
    Create                   CreateFunc
    Read                     ReadFunc
    Update                   UpdateFunc
    Delete                   DeleteFunc
    Exists                   ExistsFunc
    CreateContext            CreateContextFunc
    ReadContext              ReadContextFunc
    UpdateContext            UpdateContextFunc
    DeleteContext            DeleteContextFunc
    CreateWithoutTimeout     CreateContextFunc
    ReadWithoutTimeout       ReadContextFunc
    UpdateWithoutTimeout     UpdateContextFunc
    DeleteWithoutTimeout     DeleteContextFunc
    CustomizeDiff            CustomizeDiffFunc
    Importer                 *ResourceImporter
    DeprecationMessage       string
    Timeouts                 *ResourceTimeout
    Description              string
    UseJSONNumber            bool
}

Framework

In the Framework, you define your provider's resources by adding them to your provider's Resources method.

The Resources method on your provider.Provider returns a slice of functions that return types that implement the resource.Resource interface for each resource your provider supports.

The following code shows how you add a resource to your provider with the Framework.

func (p *provider) Resources(ctx context.Context) []func() resource.Resource {
    return []func() resource.Resource{
        func() resource.Resource {
            return resourceTypeExample{}
        },
    }
}

The resource.Resource interface requires Metadata, Schema, Create, Read, Update, and Delete methods.

The Schema method returns a schema.Schema struct which defines your resource's attributes.

The Metadata method returns a type name that you define.

The following code shows how you define a resource.Resource which implements these methods with the Framework.

type resourceExample struct{}

func (r *resourceExample) Metadata(ctx context.Context, req resource.MetadataRequest, resp *resource.MetadataResponse) {
    /* ... */
}

func (r *resourceExample) Schema(ctx context.Context, req resource.SchemaRequest, resp *resource.SchemaResponse) {
    /* ... */
}

func (r *resourceExample) Create(ctx context.Context, req resource.CreateRequest, resp *resource.CreateResponse) {
    /* ... */
}

func (r *resourceExample) Read(ctx context.Context, req resource.ReadRequest, resp *resource.ReadResponse) {
    /* ... */
}

func (r *resourceExample) Update(ctx context.Context, req resource.UpdateRequest, resp *resource.UpdateResponse) {
    /* ... */
}

func (r *resourceExample) Delete(ctx context.Context, req resource.DeleteRequest, resp *resource.DeleteResponse) {
    /* ... */
}

Refer to the Resources - CRUD functions page in this guide to learn how to implement the resource.Resource interface.

Migration Notes

Remember the following differences between SDKv2 and the Framework when completing the migration.

SDKv2 uses schema.Resource structs to define resources. These structs have a Schema field which holds a schema.Schema to define the resource's attributes and behavior. In the Framework, you define a type that implements the resource.Resource interface, which includes a Schema method that returns your resource's schema.
SDKv2 implements a resource's CRUD operations as functions on the schema.Resource. In the Framework, you define a type that implements the resource.Resource interface. The resource interface contains the functions that define your resource's CRUD operations.

Example

The following examples show how to migrate portions of the tls provider.

For a complete example, clone the terraform-provider-tls repository and compare the resource_private_key.go file in v3.4.0 with the file after the migration.

SDKv2

In SDKv2, the ResourcesMap field on the schema.Provider struct holds a map[string]*schemaResource. A typical pattern is to implement a function that returns schema.Resource.

The following example from the provider.go file defines a tls_private_key resource within the provider schema.

func New() (*schema.Provider, error) {
    return &schema.Provider {
        ResourcesMap: map[string]*schema.Resource {
            "tls_private_key": resourcePrivateKey(),
            /* ... */

The following example from the resource_private_key.go file defines the resource schema.

func resourcePrivateKey() *schema.Resource {
    return &schema.Resource{
        CreateContext: createResourcePrivateKey,
        DeleteContext: deleteResourcePrivateKey,
        ReadContext:   readResourcePrivateKey,

        Description: "Creates a PEM /* ... */",

        Schema: map[string]*schema.Schema{
            "algorithm": {
                Type:             schema.TypeString,
                Required:         true,
                ForceNew:         true,
                ValidateDiagFunc: validation.ToDiagFunc(validation.StringInSlice(SupportedAlgorithmsStr(), false)),
                Description: "Name of the algorithm to use when generating the private key. " +
                    "Currently-supported values are `RSA`, `ECDSA` and `ED25519`.",
            },
            /* ... */

Framework

The following shows the same section of provider code after the migration.

This code defines the tls_private_key resource by mapping the resource name to the privateKeyResourceType struct.

func (p *TlsProvider) Resources(_ context.Context) []func() resource.Resource {
    return []func() resource.Resource{
        func() resource.Resource {
            return &privateKeyResource{}
        },
        /* ... */
    }
}

This code defines the Schema and Metadata methods for the privateKeyResource.

func (r *privateKeyResource) Metadata(ctx context.Context, req resource.MetadataRequest, resp *resource.MetadataResponse) {
    resp.TypeName = "tls_private_key"
}

func (r *privateKeyResource) Schema(_ context.Context, _ resource.SchemaRequest, resp *resource.SchemaResponse) {
    resp.Schema = schema.Schema{
        Attributes: map[string]schema.Attribute{
            // Required attributes
            "algorithm": schema.StringAttribute{
                Required: true,
                PlanModifiers: []planmodifier.String{
                    stringplanmodifier.RequiresReplace(),
                },
                Validators: []validator.String{
                    stringvalidator.OneOf(supportedAlgorithmsAttrValue()...),
                },
                Description: "Name of the algorithm to use when generating the private key. " +
                    fmt.Sprintf("Currently-supported values are: `%s`. ", strings.Join(supportedAlgorithmsStr(), "`, `")),
            },
            /* ... */
        },
    }
}