backstage/docs/getting-started/create-an-app.md

id, title, description

id	title	description
create-an-app	Create an App	Documentation on Creating an App

To get set up quickly with your own Backstage project you can create a Backstage App.

A Backstage App is a monorepo setup with lerna that includes everything you need to run Backstage in your own environment.

If you intend to develop a plugin or contribute to the Backstage project, you may want to Run Backstage Locally instead.

Create an app

To create a Backstage app, you will need to have Node.js Active LTS Release installed (currently v14).

Backstage provides a utility for creating new apps. It guides you through the initial setup of selecting the name of the app and a database for the backend. The database options are either SQLite or PostgreSQL, where the latter requires you to set up a separate database instance. If in doubt, choose SQLite, but don't worry about the choice, it's easy to change later! Here is a tutorial for it.

The easiest way to run the create app package is with npx:

npx @backstage/create-app

This will create a new Backstage App inside the current folder. The name of the app-folder is the name that was provided when prompted.

Inside that directory, it will generate all the files and folder structure needed for you to run your app.

General folder structure

Below is a simplified layout of the files and folders generated when creating an app.

app
├── app-config.yaml
├── catalog-info.yaml
├── lerna.json
├── package.json
└── packages
    ├── app
    └── backend

• app-config.yaml: Main configuration file for the app. See Configuration for more information.
• catalog-info.yaml: Catalog Entities descriptors. See Descriptor Format of Catalog Entities to get started.
• lerna.json: Contains information about workspaces and other lerna configuration needed for the monorepo setup.
• package.json: Root package.json for the project. Note: Be sure that you don't add any npm dependencies here as they probably should be installed in the intended workspace rather than in the root.
• packages/: Lerna leaf packages or "workspaces". Everything here is going to be a separate package, managed by lerna.
• packages/app/: An fully functioning Backstage frontend app, that acts as a good starting point for you to get to know Backstage.
• packages/backend/: We include a backend that helps power features such as Authentication, Software Catalog, Software Templates and TechDocs amongst other things.

Troubleshooting

The create app command doesn't always work as expected, this is a collection of some of the commonly encountered issues and solutions.

Couldn't find any versions for "file-saver"

You may encounter the following error message:

Couldn't find any versions for "file-saver" that matches "eligrey-FileSaver.js-1.3.8.tar.gz-art-external"

This is likely because you have a globally configured npm proxy, which breaks the installation of the material-table dependency. This is a known issue and being worked on in material-table, but for now you can work around it using the following:

NPM_CONFIG_REGISTRY=https://registry.npmjs.org npx @backstage/create-app

Can't find Python executable "python"

The install process may also fail if no Python installation is available. Python is commonly available in most systems already, but if it isn't you can head for example here to install it.

Could not execute command yarn install

Install yarn on your system with npm install --global yarn or for more details refer to the prerequisites

Run the app

When the installation is complete you can open the app folder and start the app.

cd my-backstage-app
yarn dev

The yarn dev command will run both the frontend and backend as separate processes (named [0] and [1]) in the same window. When the command finishes running, it should open up a browser window displaying your app. If not, you can open a browser and directly navigate to the frontend at http://localhost:3000.

Now you're free to hack away on your own Backstage installation!

As you get more experienced with the app, in future you can run just the frontend with yarn start in one window, and the backend with yarn start-backend in a different window.

Linking in local Backstage packages

It can often be useful to try out changes to the packages in the main Backstage repo within your own app. For example if you want to make modifications to @backstage/core-plugin-api and try them out in your app.

To link in external packages, add them to your package.json and lerna.json workspace paths. These can be either relative or absolute paths with or without globs. For example:

"packages": [
  "packages/*",
  "plugins/*",
  "../backstage/packages/core-plugin-api", // New path added to work on @backstage/core-plugin-api
],

Then reinstall packages to make yarn set up symlinks:

yarn install

With this in place you can now modify the @backstage/core-plugin-api package within the main repo, and have those changes be reflected and tested in your app. Simply run your app using yarn dev (or yarn start for just frontend) as normal.

Note that for backend packages you need to make sure that linked packages are not dependencies of any non-linked package. If you for example want to work on @backstage/backend-common, you need to also link in other backend plugins and packages that depend on @backstage/backend-common, or temporarily disable those plugins in your backend. This is because the transformation of backend module tree stops whenever a non-local package is encountered, and from that point node will require packages directly for that entire module subtree.

Type checking can also have issues when linking in external packages, since the linked in packages will use the types in the external project and dependency version mismatches between the two projects may cause errors. To fix any of those errors you need to sync versions of the dependencies in the two projects. A simple way to do this can be to copy over yarn.lock from the external project and run yarn install, although this is quite intrusive and can cause other issues in existing projects, so use this method with care. It can often be best to simply ignore the type errors, as app serving will work just fine anyway.

Another issue with type checking is that the incremental type cache doesn't invalidate correctly for the linked in packages, causing type checking to not reflect changes made to types. You can work around this by either setting compilerOptions.incremental = false in tsconfig.json, or by deleting the types cache folder dist-types before running yarn tsc.