1# Working with the React UI 2 3This file explains how to work with the React-based Prometheus UI. 4 5## Introduction 6 7The [React-based](https://reactjs.org/) Prometheus UI was bootstrapped using [Create React App](https://github.com/facebook/create-react-app), a popular toolkit for generating React application setups. You can find general information about Create React App on [their documentation site](https://create-react-app.dev/). 8 9Instead of plain JavaScript, we use [TypeScript](https://www.typescriptlang.org/) to ensure typed code. 10 11## Development environment 12 13To work with the React UI code, you will need to have the following tools installed: 14 15* The [Node.js](https://nodejs.org/) JavaScript runtime. 16* The [Yarn](https://yarnpkg.com/) package manager. 17* *Recommended:* An editor with TypeScript, React, and [ESLint](https://eslint.org/) linting support. See e.g. [Create React App's editor setup instructions](https://create-react-app.dev/docs/setting-up-your-editor/). If you are not sure which editor to use, we recommend using [Visual Studio Code](https://code.visualstudio.com/docs/languages/typescript). Make sure that [the editor uses the project's TypeScript version rather than its own](https://code.visualstudio.com/docs/typescript/typescript-compiling#_using-the-workspace-version-of-typescript). 18 19**NOTE**: When using Visual Studio Code, be sure to open the `web/ui/react-app` directory in the editor instead of the root of the repository. This way, the right ESLint and TypeScript configuration will be picked up from the React workspace. 20 21## Installing npm dependencies 22 23The React UI depends on a large number of [npm](https://www.npmjs.com/) packages. These are not checked in, so you will need to download and install them locally via the Yarn package manager: 24 25 yarn 26 27Yarn consults the `package.json` and `yarn.lock` files for dependencies to install. It creates a `node_modules` directory with all installed dependencies. 28 29**NOTE**: Remember to change directory to `web/ui/react-app` before running this command and the following commands. 30 31## Running a local development server 32 33You can start a development server for the React UI outside of a running Prometheus server by running: 34 35 yarn start 36 37This will open a browser window with the React app running on http://localhost:3000/. The page will reload if you make edits to the source code. You will also see any lint errors in the console. 38 39Due to a `"proxy": "http://localhost:9090"` setting in the `package.json` file, any API requests from the React UI are proxied to `localhost` on port `9090` by the development server. This allows you to run a normal Prometheus server to handle API requests, while iterating separately on the UI. 40 41 [browser] ----> [localhost:3000 (dev server)] --(proxy API requests)--> [localhost:9090 (Prometheus)] 42 43## Running tests 44 45Create React App uses the [Jest](https://jestjs.io/) framework for running tests. To run tests in interactive watch mode: 46 47 yarn test 48 49To generate an HTML-based test coverage report, run: 50 51 CI=true yarn test --coverage 52 53This creates a `coverage` subdirectory with the generated report. Open `coverage/lcov-report/index.html` in the browser to view it. 54 55The `CI=true` environment variable prevents the tests from being run in interactive / watching mode. 56 57See the [Create React App documentation](https://create-react-app.dev/docs/running-tests/) for more information about running tests. 58 59## Linting 60 61We define linting rules for the [ESLint](https://eslint.org/) linter. We recommend integrating automated linting and fixing into your editor (e.g. upon save), but you can also run the linter separately from the command-line. 62 63To detect and automatically fix lint errors, run: 64 65 yarn lint 66 67This is also available via the `react-app-lint-fix` target in the main Prometheus `Makefile`. 68 69## Building the app for production 70 71To build a production-optimized version of the React app to a `build` subdirectory, run: 72 73 yarn build 74 75**NOTE:** You will likely not need to do this directly. Instead, this is taken care of by the `build` target in the main Prometheus `Makefile` when building the full binary. 76 77## Integration into Prometheus 78 79To build a Prometheus binary that includes a compiled-in version of the production build of the React app, change to the root of the repository and run: 80 81 make build 82 83This installs npm dependencies via Yarn, builds a production build of the React app, and then finally compiles in all web assets into the Prometheus binary. 84