Configure Data Sources

Data sources 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 data sources by adding the Configure method.

Prepare Provider Configure Method

Implement the provider.ConfigureResponse.DataSourceData 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 data sources 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 data sources:

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

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

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

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

In this example, the ExampleCloudProvider type itself is made available for data sources:

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

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

Define Data Source Configure Method

Implement the datasource.DataSourceWithConfigure interface which receives the provider configured data from the Provider interface Configure method and saves it into the datasource.DataSource interface implementation.

The datasource.DataSourceWithConfigure interface Configure method is called during execution of the terraform validate, terraform plan and terraform apply commands when the ValidateDataResourceConfig RPC is sent. Additionally, the datasource.DataSourceWithConfigure interface Configure method is called during execution of the terraform plan and terraform apply commands when the ReadDataSource RPC is sent.

Note that Terraform calling the ValidateDataResourceConfig 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 data source uses during Read:

// With the datasource.DataSource implementation
type ThingDataSource struct {
  client *http.Client
}

func (d *ThingDataSource) Configure(ctx context.Context, req datasource.ConfigureRequest, resp *datasource.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 Data Source 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 *ThingDataSource) Read(ctx context.Context, req datasource.ReadRequest, resp *datasource.ReadResponse) {
  // 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")
  /* ... */
}