Introduce Generic Settings Resource (#2997)

* WIP: Generic Settings Resource

* retries as before

* fix

* fix update

* Generic settings resource revamped

* Do not retry on reads, and only retry on resource conflict

* fix

provider/provider.go

@@ -105,7 +105,6 @@ func DatabricksProvider() *schema.Provider {
 			"databricks_cluster":                     clusters.ResourceCluster(),
 			"databricks_cluster_policy":              policies.ResourceClusterPolicy(),
 			"databricks_dbfs_file":                   storage.ResourceDbfsFile(),
-			"databricks_default_namespace_setting":   settings.ResourceDefaultNamespaceSetting(),
 			"databricks_directory":                   workspace.ResourceDirectory(),
 			"databricks_entitlements":                scim.ResourceEntitlements(),
 			"databricks_external_location":           catalog.ResourceExternalLocation(),
@@ -178,6 +177,9 @@ func DatabricksProvider() *schema.Provider {
 		},
 		Schema: providerSchema(),
 	}
+	for name, resource := range settings.AllSettingsResources() {
+		p.ResourcesMap[fmt.Sprintf("databricks_%s_setting", name)] = resource
+	}
 	p.ConfigureContextFunc = func(ctx context.Context, d *schema.ResourceData) (any, diag.Diagnostics) {
 		if p.TerraformVersion != "" {
 			useragent.WithUserAgentExtra("terraform", p.TerraformVersion)

settings/all_settings.go

@@ -0,0 +1,20 @@
+package settings
+
+import (
+	"github.com/databricks/databricks-sdk-go"
+	"github.com/databricks/databricks-sdk-go/service/settings"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+)
+
+// Instructions for adding a new setting:
+//
+//  1. Create a new file named resource_<SETTING_NAME>.go in this directory.
+//  2. In that file, create an instance of either the workspaceSettingDefinition or accountSettingDefinition interface for your setting.
+//     If the setting name is user-settable, it will be provided in the third argument to the updateFunc method. If not, you must set the
+//     SettingName field appropriately. You must also set AllowMissing: true and the field mask to the field to update.
+//  3. Add a new entry to the AllSettingsResources map below. The final resource name will be "databricks_<SETTING_NAME>_setting".
+func AllSettingsResources() map[string]*schema.Resource {
+	return map[string]*schema.Resource{
+		"default_namespace": makeSettingResource[settings.DefaultNamespaceSetting, *databricks.WorkspaceClient](defaultNamespaceSetting),
+	}
+}

settings/generic_setting.go

@@ -0,0 +1,311 @@
+package settings
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"reflect"
+
+	"github.com/databricks/databricks-sdk-go"
+	"github.com/databricks/databricks-sdk-go/apierr"
+	"github.com/databricks/terraform-provider-databricks/common"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+)
+
+func retryOnEtagError[Req, Resp any](f func(req Req) (Resp, error), firstReq Req, updateReq func(req *Req, newEtag string), retriableErrors []error) (Resp, error) {
+	req := firstReq
+	// Retry once on etag error.
+	res, err := f(req)
+	if err == nil {
+		return res, nil
+	}
+	if !isRetriableError(err, retriableErrors) {
+		return res, err
+	}
+	etag, err := getEtagFromError(err)
+	if err != nil {
+		return res, err
+	}
+	updateReq(&req, etag)
+	return f(req)
+}
+
+func isRetriableError(err error, retriableErrors []error) bool {
+	for _, retriableError := range retriableErrors {
+		if errors.Is(err, retriableError) {
+			return true
+		}
+	}
+	return false
+}
+
+func getEtagFromError(err error) (string, error) {
+	errorInfos := apierr.GetErrorInfo(err)
+	if len(errorInfos) > 0 {
+		metadata := errorInfos[0].Metadata
+		if etag, ok := metadata["etag"]; ok {
+			return etag, nil
+		}
+	}
+	return "", fmt.Errorf("error fetching the default workspace namespace settings: %w", err)
+}
+
+type genericSettingDefinition[T, U any] interface {
+	// Returns the struct corresponding to the setting. The schema of the Terraform resource will be generated from this struct.
+	SettingStruct() T
+
+	// Read the setting from the server. The etag is provided as the third argument.
+	Read(ctx context.Context, c U, etag string) (*T, error)
+
+	// Update the setting to the value specified by t, and return the new etag.
+	Update(ctx context.Context, c U, t T) (string, error)
+
+	// Delete the setting with the given etag, and return the new etag.
+	Delete(ctx context.Context, c U, etag string) (string, error)
+
+	// Get the etag from the setting.
+	GetETag(t *T) string
+
+	// Update the etag in the setting.
+	SetETag(t *T, newEtag string)
+}
+
+func getEtag[T any](t T) string {
+	rv := reflect.ValueOf(t)
+	if rv.Kind() == reflect.Ptr {
+		rv = rv.Elem()
+	}
+	return rv.FieldByName("Etag").String()
+}
+
+func setEtag[T any](t T, newEtag string) {
+	rv := reflect.ValueOf(t)
+	if rv.Kind() == reflect.Ptr {
+		rv = rv.Elem()
+	}
+	rv.FieldByName("Etag").SetString(newEtag)
+}
+
+type workspaceSettingDefinition[T any] genericSettingDefinition[T, *databricks.WorkspaceClient]
+
+// A workspace setting is a setting that is scoped to a workspace.
+type workspaceSetting[T any] struct {
+	// The struct corresponding to the setting. The schema of the Terraform resource will be generated from this struct.
+	// This struct must have an Etag field of type string.
+	settingStruct T
+
+	// Read the setting from the server. The etag is provided as the third argument.
+	readFunc func(ctx context.Context, w *databricks.WorkspaceClient, etag string) (*T, error)
+
+	// Update the setting to the value specified by t, and return the new etag. If the setting name is user-settable,
+	// it will be provided in the third argument. If not, you must set the SettingName field appropriately. You must
+	// also set AllowMissing: true and the field mask to the field to update.
+	updateFunc func(ctx context.Context, w *databricks.WorkspaceClient, setting T) (string, error)
+
+	// Delete the setting with the given etag, and return the new etag.
+	deleteFunc func(ctx context.Context, w *databricks.WorkspaceClient, etag string) (string, error)
+}
+
+func (w workspaceSetting[T]) SettingStruct() T {
+	return w.settingStruct
+}
+func (w workspaceSetting[T]) Read(ctx context.Context, c *databricks.WorkspaceClient, etag string) (*T, error) {
+	return w.readFunc(ctx, c, etag)
+}
+func (w workspaceSetting[T]) Update(ctx context.Context, c *databricks.WorkspaceClient, t T) (string, error) {
+	return w.updateFunc(ctx, c, t)
+}
+func (w workspaceSetting[T]) Delete(ctx context.Context, c *databricks.WorkspaceClient, etag string) (string, error) {
+	return w.deleteFunc(ctx, c, etag)
+}
+func (w workspaceSetting[T]) GetETag(t *T) string {
+	return getEtag(t)
+}
+func (w workspaceSetting[T]) SetETag(t *T, newEtag string) {
+	setEtag(t, newEtag)
+}
+
+var _ workspaceSettingDefinition[struct{}] = workspaceSetting[struct{}]{}
+
+type accountSettingDefinition[T any] genericSettingDefinition[T, *databricks.AccountClient]
+
+// An account setting is a setting that is scoped to a workspace.
+type accountSetting[T any] struct {
+	// The struct corresponding to the setting. The schema of the Terraform resource will be generated from this struct.
+	// This struct must have an Etag field of type string.
+	settingStruct T
+
+	// Read the setting from the server. The etag is provided as the third argument.
+	readFunc func(ctx context.Context, w *databricks.AccountClient, etag string) (*T, error)
+
+	// Update the setting to the value specified by t, and return the new etag. If the setting name is user-settable,
+	// it will be provided in the third argument. If not, you must set the SettingName field appropriately. You must
+	// also set AllowMissing: true and the field mask to the field to update.
+	updateFunc func(ctx context.Context, w *databricks.AccountClient, setting T) (string, error)
+
+	// Delete the setting with the given etag, and return the new etag.
+	deleteFunc func(ctx context.Context, w *databricks.AccountClient, etag string) (string, error)
+}
+
+func (w accountSetting[T]) SettingStruct() T {
+	return w.settingStruct
+}
+func (w accountSetting[T]) Read(ctx context.Context, c *databricks.AccountClient, etag string) (*T, error) {
+	return w.readFunc(ctx, c, etag)
+}
+func (w accountSetting[T]) Update(ctx context.Context, c *databricks.AccountClient, t T) (string, error) {
+	return w.updateFunc(ctx, c, t)
+}
+func (w accountSetting[T]) Delete(ctx context.Context, c *databricks.AccountClient, etag string) (string, error) {
+	return w.deleteFunc(ctx, c, etag)
+}
+func (w accountSetting[T]) GetETag(t *T) string {
+	return getEtag(t)
+}
+func (w accountSetting[T]) SetETag(t *T, newEtag string) {
+	setEtag(t, newEtag)
+}
+
+var _ accountSettingDefinition[struct{}] = accountSetting[struct{}]{}
+
+func makeSettingResource[T, U any](defn genericSettingDefinition[T, U]) *schema.Resource {
+	resourceSchema := common.StructToSchema(defn.SettingStruct(),
+		func(s map[string]*schema.Schema) map[string]*schema.Schema {
+			s["etag"].Computed = true
+			// Note: this may not always be computed, but it is for the default namespace setting. If other settings
+			// are added for which setting_name is not computed, we'll need to expose this somehow as part of the setting
+			// definition.
+			s["setting_name"].Computed = true
+			return s
+		})
+	createOrUpdateRetriableErrors := []error{apierr.ErrNotFound, apierr.ErrResourceConflict}
+	deleteRetriableErrors := []error{apierr.ErrResourceConflict}
+	createOrUpdate := func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient, setting T) error {
+		common.DataToStructPointer(d, resourceSchema, &setting)
+		var res string
+		switch defn := defn.(type) {
+		case workspaceSettingDefinition[T]:
+			w, err := c.WorkspaceClient()
+			if err != nil {
+				return err
+			}
+			res, err = retryOnEtagError[T, string](
+				func(setting T) (string, error) {
+					return defn.Update(ctx, w, setting)
+				},
+				setting,
+				defn.SetETag,
+				createOrUpdateRetriableErrors)
+			if err != nil {
+				return err
+			}
+		case accountSettingDefinition[T]:
+			a, err := c.AccountClient()
+			if err != nil {
+				return err
+			}
+			res, err = retryOnEtagError(
+				func(setting T) (string, error) {
+					return defn.Update(ctx, a, setting)
+				},
+				setting,
+				defn.SetETag,
+				createOrUpdateRetriableErrors)
+			if err != nil {
+				return err
+			}
+		default:
+			return fmt.Errorf("unexpected setting type: %T", defn)
+		}
+		d.SetId(res)
+		return nil
+	}
+
+	return common.Resource{
+		Schema: resourceSchema,
+		Create: func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient) error {
+			var setting T
+			return createOrUpdate(ctx, d, c, setting)
+		},
+		Read: func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient) error {
+			var res *T
+			switch defn := defn.(type) {
+			case workspaceSettingDefinition[T]:
+				w, err := c.WorkspaceClient()
+				if err != nil {
+					return err
+				}
+				res, err = defn.Read(ctx, w, d.Id())
+				if err != nil {
+					return err
+				}
+			case accountSettingDefinition[T]:
+				a, err := c.AccountClient()
+				if err != nil {
+					return err
+				}
+				res, err = defn.Read(ctx, a, d.Id())
+				if err != nil {
+					return err
+				}
+			default:
+				return fmt.Errorf("unexpected setting type: %T", defn)
+			}
+			err := common.StructToData(res, resourceSchema, d)
+			if err != nil {
+				return err
+			}
+			// Update the etag. The server will accept any etag and respond
+			// with a response which is at least as recent as the etag.
+			// Updating, while not always necessary, ensures that the
+			// server responds with an updated response.
+			d.SetId(defn.GetETag(res))
+			return nil
+		},
+		Update: func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient) error {
+			var setting T
+			defn.SetETag(&setting, d.Id())
+			return createOrUpdate(ctx, d, c, setting)
+		},
+		Delete: func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient) error {
+			var etag string
+			updateETag := func(req *string, newEtag string) { *req = newEtag }
+			switch defn := defn.(type) {
+			case workspaceSettingDefinition[T]:
+				w, err := c.WorkspaceClient()
+				if err != nil {
+					return err
+				}
+				etag, err = retryOnEtagError(
+					func(etag string) (string, error) {
+						return defn.Delete(ctx, w, etag)
+					},
+					d.Id(),
+					updateETag,
+					deleteRetriableErrors)
+				if err != nil {
+					return err
+				}
+			case accountSettingDefinition[T]:
+				a, err := c.AccountClient()
+				if err != nil {
+					return err
+				}
+				etag, err = retryOnEtagError(
+					func(etag string) (string, error) {
+						return defn.Delete(ctx, a, etag)
+					},
+					d.Id(),
+					updateETag,
+					deleteRetriableErrors)
+				if err != nil {
+					return err
+				}
+			default:
+				return fmt.Errorf("unexpected setting type: %T", defn)
+			}
+			d.SetId(etag)
+			return nil
+		},
+	}.ToResource()
+}