Configure Ephemeral Resources

Ephemeral Resources may require provider-level data or remote system clients to operate correctly. The framework supports the ability to configure this data and/or clients once within the provider, then pass that information to ephemeral resources by adding the Configure method.

Prepare Provider Configure Method

Implement the provider.ConfigureResponse.EphemeralResourceData field in the Provider interface Configure method. This value can be set to any type, whether an existing client or vendor SDK type, a provider-defined custom type, or the provider implementation itself. It is recommended to use pointer types so that ephemeral resources can determine if this value was configured before attempting to use it.

During execution of the terraform plan and terraform apply commands, Terraform calls the ConfigureProvider RPC, in which the framework calls the provider.Provider interface Configure method.

In this example, the Go standard library net/http.Client is configured in the provider, and made available for ephemeral resources:

// With the provider.Provider implementation
func (p *ExampleCloudProvider) Configure(ctx context.Context, req provider.ConfigureRequest, resp *provider.ConfigureResponse) {
  resp.EphemeralResourceData = &http.Client{/* ... */}
}

In this example, the code defines an ExampleClient type that is made available for ephemeral resources:

type ExampleClient struct {
  /* ... */
}

// With the provider.Provider implementation
func (p *ExampleCloudProvider) Configure(ctx context.Context, req provider.ConfigureRequest, resp *provider.ConfigureResponse) {
  resp.EphemeralResourceData = &ExampleClient{/* ... */}
}

In this example, the ExampleCloudProvider type itself is made available for ephemeral resources:

// With the provider.Provider implementation
type ExampleCloudProvider struct {
  /* ... */
}

func (p *ExampleCloudProvider) Configure(ctx context.Context, req provider.ConfigureRequest, resp *provider.ConfigureResponse) {
  resp.EphemeralResourceData = p
}

Define Ephemeral Resource Configure Method

Implement the ephemeral.EphemeralResourceWithConfigure interface which receives the provider configured data from the Provider interface Configure method and saves it into the ephemeral.EphemeralResource interface implementation.

The ephemeral.EphemeralResourceWithConfigure interface Configure method is called during execution of the terraform validate, terraform plan and terraform apply commands when the ValidateEphemeralResourceConfig RPC is sent. Additionally, the ephemeral.EphemeralResourceWithConfigure interface Configure method is called during execution of the terraform plan and terraform apply commands when the OpenEphemeralResource RPC is sent.

Note that Terraform calling the ValidateEphemeralResourceConfig RPC would not call the ConfigureProvider RPC first, so implementations need to account for that situation. Configuration validation in Terraform occurs without provider configuration ("offline").

In this example, the provider configured the Go standard library net/http.Client which the ephemeral resource uses during Open:

// With the ephemeral.EphemeralResource implementation
type ThingEphemeralResource struct {
  client *http.Client
}

func (d *ThingEphemeralResource) Configure(ctx context.Context, req ephemeral.ConfigureRequest, resp *ephemeral.ConfigureResponse) {
  // Always perform a nil check when handling ProviderData because Terraform
  // sets that data after it calls the ConfigureProvider RPC.
  if req.ProviderData == nil {
    return
  }

  client, ok := req.ProviderData.(*http.Client)

  if !ok {
    resp.Diagnostics.AddError(
      "Unexpected Ephemeral Resource Configure Type",
      fmt.Sprintf("Expected *http.Client, got: %T. Please report this issue to the provider developers.", req.ProviderData),
    )

    return
  }

  d.client = client
}

func (d *ThingEphemeralResource) Open(ctx context.Context, req ephemeral.OpenRequest, resp *ephemeral.OpenResponse) {
  // Prevent panic if the provider has not been configured.
  if d.client == nil {
    resp.Diagnostics.AddError(
      "Unconfigured HTTP Client",
      "Expected configured HTTP client. Please report this issue to the provider developers.",
    )

    return
  }

  httpResp, err := d.client.Get("https://example.com")
  /* ... */
}