Migrating resources

This page explains how to migrate a resource's schema from SDKv2 to the plugin framework. To migrate a resource, implement the resource schema and related functions in the framework, and then add the resource to your provider. In SDKv2, developers usually implement resources as functions that return a resource schema. In the framework, resources are defined as types that implement the correct interface.

Background

Resources are an abstraction that allow Terraform to manage infrastructure. objects. To develop a resource for your provider, define functionality that maps to API operations so that Terraform can create, read, update, and delete infrastructure of that resource's type. Resource schemas define resource fields, give Terraform metadata about those fields, and define how the resource behaves.

Refer to Resources in the framework documentation for details on implementing resources in the framework.

Migrating resource schema

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)

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 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
}

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 an example resource that implements resource.Resource interface.

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 migrating resource schema.

• SDKv2 uses schema.Resource structs to define resources. These structs have a Schema field, which holds a schema.Schema struct that defines 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.
• By default, SDKv2 demotes certain resource schema definition and data consistency errors so that they are only visible as Terraform warning logs. After migration, these errors are always visible to practitioners and prevent further Terraform operations. The SDKv2 resource data consistency errors documentation describe how to find these errors in SDKv2 resources and potential solutions prior to migrating. Refer to CRUD - Resolving Data Consistency Errors for framework solutions during migration.

Examples

The following examples demonstrate migrating a resource from SDKv2 to the framework.

Migrate a resource

Migrating a resource from the SDKv2 to the framework typically involves implmenting a type that satisfies the resource.Resource interface and adding it to the return value of your providers Resources function.

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.

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

This code defines the example_resource resource by mapping the resource name to the exampleResource struct.

func exampleResource() *schema.Resource {
    return &schema.Resource{
        CreateContext: createResource,
        DeleteContext: deleteResource,
        ReadContext:   readResource,

        Schema: map[string]*schema.Schema{
            "attribute": {
                Type:             schema.TypeString,
                Required:         true,
                ForceNew:         true,
                ValidateDiagFunc: validation.ToDiagFunc(validation.StringInSlice([]string{'a', 'b'}, false)),
            },
            /* ... */

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

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

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

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

func (r *exampleResource) Schema(_ context.Context, _ resource.SchemaRequest, resp *resource.SchemaResponse) {
    resp.Schema = schema.Schema{
        Attributes: map[string]schema.Attribute{
            // Required attributes
            "attribute": schema.StringAttribute{
                Required: true,
                PlanModifiers: []planmodifier.String{
                    stringplanmodifier.RequiresReplace(),
                },
                Validators: []validator.String{
                    stringvalidator.OneOf([]string{"a", "b"}...),
                },
            },
            /* ... */
        },
    }
}

Refer to the Migrating schema page in this migration guide to learn how to migrate your resource's schema to the framework.

Migrating resource implementation

Once you have migrated your resource schema to the framework, you must implement the resource functionality in your resource's type. To do so, write code that satisfies the resource.Resource interface. At a minimum, you must migrate the create, read, update, delete (CRUD) functions for your resource, as well as import functionality if your SDKv2 provider supports it. Some resources may implement additional functionality that you must migrate to the framework, as well.

1. To migrate your resource's CRUD functionality, refer to the Resources - CRUD functions page in this guide.
2. To migrate import functionality, refer to the Resources - Resource import page in this guide.
3. Some resources may require plan modification during Terraform operations. If your SDKv2 resource uses CustomizeDiff functions to modify the plan, refer to the Resources - Plan modification page in this guide.
4. When a resource's implmentation changes in your provider in ways that break compatability with older versions, your provider may implement state upgraders to migrate resource state from one version to another. If your SDKv2 provider implements StateUpgraders, refer to the Resources - State upgrading page in this guide to migrate them to UpgradeState functions in the framework.
5. Some resources may require timeouts for long-running operations. Refer to the Resources - Timeouts page in this guide to implement resource timeouts in the framework.