Fix databricks_metastore_assignment config drift (#1156)

* Fix `databricks_metastore_assignment` config drift

Fixed `databricks_metastore_assignment` configuration drift by properly deleting metastore assignment and detecting manual changes from Account console. This also means that de-assigned metastore from a workspace would mark it as remotely removed. Manual assignment of different metastore would also trigger resource updates.

Fixes #1146
Closes #1147

Author: nfx

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Version changelog
 
+## 0.5.2
+
+* Fixed `databricks_metastore_assignment` configuration drift by properly deleting metastore assignment and detecting manual changes from Account console. This also means that de-assigned metastore from a workspace would mark it as remotely removed. Manual assignment of different metastore would also trigger resource updates ([#1146](https://github.com/databrickslabs/terraform-provider-databricks/issues/1146)).
+
 ## 0.5.1
 
 * Added an extended documentation from provisioning AWS PrivateLink workspace ([#1084](https://github.com/databrickslabs/terraform-provider-databricks/pull/1084)).

catalog/resource_metastore_assignment.go

@@ -33,9 +33,17 @@ func (a MetastoreAssignmentAPI) updateMetastoreAssignment(ma MetastoreAssignment
 	return a.client.Patch(a.context, path, ma)
 }
 
-func (a MetastoreAssignmentAPI) clearMetastoreAssignment(workspaceID string) error {
+func (a MetastoreAssignmentAPI) getAssignedMetastoreID() (string, error) {
+	var ma MetastoreAssignment
+	err := a.client.Get(a.context, "/unity-catalog/metastore_summary", nil, &ma)
+	return ma.MetastoreID, err
+}
+
+func (a MetastoreAssignmentAPI) deleteMetastoreAssignment(workspaceID, metastoreID string) error {
 	path := fmt.Sprintf("/unity-catalog/workspaces/%s/metastore", workspaceID)
-	return a.client.Patch(a.context, path, map[string]string{})
+	return a.client.Delete(a.context, path, map[string]string{
+		"metastore_id": metastoreID,
+	})
 }
 
 func ResourceMetastoreAssignment() *schema.Resource {
@@ -56,20 +64,21 @@ func ResourceMetastoreAssignment() *schema.Resource {
 			return nil
 		},
 		Read: func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient) error {
-			// there are no working APIs at the moment to read the assignment
-			return nil
+			metastoreID, err := NewMetastoreAssignmentAPI(ctx, c).getAssignedMetastoreID()
+			d.Set("metastore_id", metastoreID)
+			return err
 		},
 		Update: func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient) error {
 			var ma MetastoreAssignment
 			common.DataToStructPointer(d, s, &ma)
 			return NewMetastoreAssignmentAPI(ctx, c).updateMetastoreAssignment(ma)
 		},
 		Delete: func(ctx context.Context, d *schema.ResourceData, c *common.DatabricksClient) error {
-			workspaceID, _, err := pi.Unpack(d)
+			workspaceID, metastoreID, err := pi.Unpack(d)
 			if err != nil {
 				return err
 			}
-			return NewMetastoreAssignmentAPI(ctx, c).clearMetastoreAssignment(workspaceID)
+			return NewMetastoreAssignmentAPI(ctx, c).deleteMetastoreAssignment(workspaceID, metastoreID)
 		},
 	}.ToResource()
 }

catalog/resource_metastore_assignment_test.go

@@ -24,6 +24,13 @@ func TestMetastoreAssignment_Create(t *testing.T) {
 					DefaultCatalogName: "hive_metastore",
 				},
 			},
+			{
+				Method:   "GET",
+				Resource: "/api/2.0/unity-catalog/metastore_summary",
+				Response: MetastoreAssignment{
+					MetastoreID: "a",
+				},
+			},
 		},
 		Resource: ResourceMetastoreAssignment(),
 		Create:   true,