Terraform Provider Actions Implementation Guide

Overview

Terraform Actions enable imperative operations during the Terraform lifecycle. Actions are experimental features that allow performing provider operations at specific lifecycle events (before/after create, update, destroy).

References:

• Terraform Plugin Framework
• Terraform Actions RFC

File Structure

Actions follow the standard service package structure:

internal/service/<service>/
├── <action_name>_action.go       # Action implementation
├── <action_name>_action_test.go  # Action tests
└── service_package_gen.go        # Auto-generated service registration

Documentation structure:

website/docs/actions/
└── <service>_<action_name>.html.markdown  # User-facing documentation

Changelog entry:

.changelog/
└── <pr_number_or_description>.txt  # Release note entry

Action Schema Definition

Actions use the Terraform Plugin Framework with a standard schema pattern:

func (a *actionType) Schema(ctx context.Context, req action.SchemaRequest, resp *action.SchemaResponse) {
    resp.Schema = schema.Schema{
        Attributes: map[string]schema.Attribute{
            // Required configuration parameters
            "resource_id": schema.StringAttribute{
                Required:    true,
                Description: "ID of the resource to operate on",
            },
            // Optional parameters with defaults
            "timeout": schema.Int64Attribute{
                Optional:    true,
                Description: "Operation timeout in seconds",
                Default:     int64default.StaticInt64(1800),
                Computed:    true,
            },
        },
    }
}

Common Schema Issues

Pay special attention to the schema definition - common issues after a first draft:

1. Type Mismatches

   • Using types.String instead of fwtypes.String in model structs
   • Using types.StringType instead of fwtypes.StringType in schema
   • Mixing framework types with plugin-framework types

2. List/Map Element Types

   // WRONG - missing ElementType
   "items": schema.ListAttribute{
       Optional: true,
   }
   
   // CORRECT
   "items": schema.ListAttribute{
       Optional:    true,
       ElementType: fwtypes.StringType,
   }
   

3. Computed vs Optional

   • Attributes with defaults must be both Optional: true and Computed: true
   • Don't mark action inputs as Computed unless they have defaults

4. Validator Imports

   // Ensure proper imports
   "github.com/hashicorp/terraform-plugin-framework-validators/int64validator"
   "github.com/hashicorp/terraform-plugin-framework-validators/stringvalidator"
   

5. Region/Provider Attribute

   • Use framework-provided region handling when available
   • Don't manually define provider-specific config in schema if framework handles it

6. Nested Attributes

   • Use appropriate nested object types for complex structures
   • Ensure nested types are properly defined

Schema Validation Checklist

Before submitting, verify:

• All attributes have descriptions
• List/Map attributes have ElementType defined
• Validators are imported and applied correctly
• Model struct uses correct framework types
• Optional attributes with defaults are marked Computed
• Code compiles without type errors
• Run go build to catch type mismatches

Action Invoke Method

The Invoke method contains the action logic:

func (a *actionType) Invoke(ctx context.Context, req action.InvokeRequest, resp *action.InvokeResponse) {
    var data actionModel
    resp.Diagnostics.Append(req.Config.Get(ctx, &data)...)

    // Create provider client
    conn := a.Meta().Client(ctx)

    // Progress updates for long-running operations
    resp.Progress.Set(ctx, "Starting operation...")

    // Implement action logic with error handling
    // Use context for timeout management
    // Poll for completion if async operation

    resp.Progress.Set(ctx, "Operation completed")
}

Key Implementation Requirements

1. Progress Reporting

• Use resp.SendProgress(action.InvokeProgressEvent{...}) for real-time updates
• Provide meaningful progress messages during long operations
• Update progress at key milestones
• Include elapsed time for long operations

2. Timeout Management

• Always include configurable timeout parameter (default: 1800s)
• Use context.WithTimeout() for API calls
• Handle timeout errors gracefully
• Validate timeout ranges (typically 60-7200 seconds)

3. Error Handling

• Add diagnostics with resp.Diagnostics.AddError()
• Provide clear error messages with context
• Include API error details when relevant
• Map provider error types to user-friendly messages
• Document all possible error cases

Example error handling:

// Handle specific errors
var notFound *types.ResourceNotFoundException
if errors.As(err, &notFound) {
    resp.Diagnostics.AddError(
        "Resource Not Found",
        fmt.Sprintf("Resource %s was not found", resourceID),
    )
    return
}

// Generic error handling
resp.Diagnostics.AddError(
    "Operation Failed",
    fmt.Sprintf("Could not complete operation for %s: %s", resourceID, err),
)

4. Provider SDK Integration

• Use provider SDK clients from a.Meta().<Service>Client(ctx)
• Handle pagination for list operations
• Implement retry logic for transient failures
• Use appropriate error types

5. Parameter Validation

• Use framework validators for input validation
• Validate resource existence before operations
• Check for conflicting parameters
• Validate against provider naming requirements

6. Polling and Waiting

For operations that require waiting for completion:

result, err := wait.WaitForStatus(ctx,
    func(ctx context.Context) (wait.FetchResult[*ResourceType], error) {
        // Fetch current status
        resource, err := findResource(ctx, conn, id)
        if err != nil {
            return wait.FetchResult[*ResourceType]{}, err
        }
        return wait.FetchResult[*ResourceType]{
            Status: wait.Status(resource.Status),
            Value:  resource,
        }, nil
    },
    wait.Options[*ResourceType]{
        Timeout:            timeout,
        Interval:           wait.FixedInterval(5 * time.Second),
        SuccessStates:      []wait.Status{"AVAILABLE", "COMPLETED"},
        TransitionalStates: []wait.Status{"CREATING", "PENDING"},
        ProgressInterval:   30 * time.Second,
        ProgressSink: func(fr wait.FetchResult[any], meta wait.ProgressMeta) {
            resp.SendProgress(action.InvokeProgressEvent{
                Message: fmt.Sprintf("Status: %s, Elapsed: %v", fr.Status, meta.Elapsed.Round(time.Second)),
            }