Stability Index · Backstage

Overview

The purpose of the Backstage Stability Index is to communicate the stability of various parts of the project. It is tracked using a scoring system where a higher score indicates a higher level of stability and is a commitment to smoother transitions between breaking changes. Importantly, the Stability Index does not supersede semver, meaning we will still adhere to semver and only do breaking changes in minor releases as long as we are on 0.x.

Each package or section is assigned a stability score between 0 and 3, with each point building on top of the previous one:

0 - Breaking changes are noted in the changelog, and documentation is updated.
1 - The changelog entry includes a clearly documented upgrade path, providing guidance for how to migrate previous usage patterns to the new version.
2 - Breaking changes always include a deprecation phase where both the old and the new APIs can be used in parallel. This deprecation must have been released for at least two weeks before the deprecated API is removed in a minor version bump.
3 - The time limit for the deprecation is 3 months instead of two weeks.

TL;DR:

0 - There's a changelog entry.
1 - There's a migration guide.
2 - 2 weeks of deprecation.
3 - 3 months of deprecation.

Packages

`example-app`

This is the packages/app package, and it serves as an example as well as utility for local development in the main Backstage repo.

Stability: N/A

`example-backend`

This is the packages/backend package, and it serves as an example as well as utility for local development in the main Backstage repo.

Stability: N/A

`backend-common`

A collection of common helpers to be used by both backend plugins, and for constructing backend packages.

Stability: 1

`catalog-client`

An HTTP client for interacting with the catalog backend. Usable both in frontend and Backend.

Stability: 0. This is a very new addition and we have some immediate changes planned.

`catalog-model`

Contains the core catalog model, and utilities for working with entities. Usable both in frontend and Backend.

Stability: 2. The catalog model is evolving, but because of the broad usage we

want to ensure some stability.

`cli`

The main toolchain used for Backstage development. The interface that is considered for stability are the various commands and options passed to those commands, as well as the environment variables read by the CLI. The build output may change over time and is not considered a breaking change unless it is likely to affect external tooling.

Stability: 2

`cli-common`

Lightweight utilities used by the various Backstage CLIs, not intended for external use.

Stability: N/A

`config`

Provides the logic and interfaces for reading static configuration.

Stability: 2

`config-loader`

Used to load in static configuration, mainly for use by the CLI and @backstage/backend-common.

Stability: 1. Mainly intended for internal use.

`core`

Section: React Components

All of the React components exported from src/components/ and src/layout/

Stability: 1. These components have not received a proper review of the API, but we also want to ensure stability.

Section: Plugin API

The parts of the core API that are used by plugins, and the way plugins expose functionality to apps and other plugins. Includes for example createPlugin, createRouteRef, createApiRef.

Stability: 2. There are planned breaking changes around the way that plugins expose features and do routing. We still commit to keeping a short deprecation period so that plugins outside of the main repo have time to migrate.

Section: App API

The APIs used exclusively in the app, such as createApp and the system icons.

Stability: 2

Section: Utility API Definitions

The type declarations of the core Utility APIs.

Stability: 2. Changes to the Utility API type declarations need time to propagate.

Section: Utility API Implementations

The interfaces and default implementations for various Utility APIs, such as ErrorApi, IdentityApi, the auth APIs, etc.

Stability: 1. Most changes to the core utility APIs will not lead to widespread breaking changes since most apps rely on the default implementations.

`core-api`

The non-visual parts of @backstage/core. Everything in this packages is re-exported from @backstage/core, and this package should not be used directly.

Stability: See @backstage/core

`create-app`

The CLI used to scaffold new Backstage projects.

Stability: 2

`dev-utils`

Provides utilities for developing plugins in isolation.

Stability: 0. This package is largely broken and needs updates.

`docgen`

Internal CLI utility for generating API Documentation.

Stability: N/A

`e2e-test`

Internal CLI utility for running e2e tests.

Stability: N/A

`storybook`

Internal storybook build for publishing stories to https://backstage.io/storybook

Stability: N/A

`test-utils`

Utilities for writing tests for Backstage plugins and apps.

Stability: 2

`test-utils-core`

Internal testing utilities that are separated out for usage in @backstage/core-api. All exports are re-exported by @backstage/test-utils. This package should not be depended on directly.

Stability: See @backstage/test-utils

`theme`

The core Backstage MUI theme along with customization utilities.

Section: TypeScript

This is the TypeScript API exported by the theme package.

Stability: 2

Section: Visual Theme

The visual theme exported by the theme packages, where for example changing a color could be considered a breaking change.

Stability: 1

Plugins

Plugins are rarely marked as stable as the @backstage/core plugin API is under heavy development.

Many backend plugins are split into "REST API" and "TypeScript Interface" sections. The "TypeScript Interface" refers to the API used to integrate the plugin into the backend.

Any plugin that is not listed below is untracked and can generally be considered unstable with a score of 0. Open a Pull Request if you want your plugin to be added!

`api-docs`

Components to discover and display API entities as an extension to the catalog plugin.

Stability: 0

`app-backend`

A backend plugin that can be used to serve the frontend app and inject configuration.

Stability: 2

`auth-backend`

A backend plugin that implements the backend portion of the various authentication flows used in Backstage.

Section: REST API

Stability: 2

Section: TypeScript Interface

Stability: 1

`catalog`

The frontend plugin for the catalog, with the table and building blocks for the entity pages.

Stability: 1. We're planning some work to overhaul how entity pages are constructed.

`catalog-backend`

The backend API for the catalog, also exposes the processing subsystem for customization of the catalog. Powers the @backstage/plugin-catalog frontend plugin.

Section: REST API

Stability: 1. There are plans to remove and rework some endpoints.

Section: TypeScript Interface

Stability: 1. There are plans to rework parts of the Processor interface.