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Overview

The ui directory contains static files and templates used in the web UI. For easier distribution they are compressed (c.f. Makefile) and statically compiled into the Prometheus binary using the embed package.

During development it is more convenient to always use the files on disk to directly see changes without recompiling. To make this work, remove the builtinassets build tag in the flags entry in .promu.yml, and then make build (or build Prometheus using go build ./cmd/prometheus).

This will serve all files from your local filesystem. This is for development purposes only.

React-app

Introduction

The react application is a monorepo composed by multiple different npm packages. The main one is react-app which contains the code of the react application.

Then you have different npm packages located in the folder modules. These packages are supposed to be used by the react-app and also by others consumers (like Thanos)

Pre-requisite

To be able to build the react application you need:

  • npm >= v7
  • node >= v20

Installing npm dependencies

The React UI depends on a large number of npm packages. These are not checked in, so you will need to move to the directory web/ui and then download and install them locally via the npm package manager:

npm install

npm consults the package.json and package-lock.json files for dependencies to install. It creates a node_modules directory with all installed dependencies.

NOTE: Do not run npm install in the react-app folder or in any sub folder of the module directory.

Upgrading npm dependencies

As it is a monorepo, when upgrading a dependency, you have to upgrade it in every packages that composed this monorepo ( aka, in all sub folder of module and in react-app)

Then you have to run the command npm install in web/ui and not in a sub folder / sub package. It won't simply work.

Running a local development server

You can start a development server for the React UI outside of a running Prometheus server by running:

npm start

This 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.

NOTE: It will reload only if you change the code in react-app folder. Any code changes in the folder module is not considered by the command npm start. In order to see the changes in the react-app you will have to run npm run build:module

Due 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.

[browser] ----> [localhost:3000 (dev server)] --(proxy API requests)--> [localhost:9090 (Prometheus)]

Running tests

To run the test for the react-app and for all modules, you can simply run:

npm test

if you want to run the test only for a specific module, you need to go to the folder of the module and run again npm test.

For example, in case you only want to run the test of the react-app, go to web/ui/react-app and run npm test

To generate an HTML-based test coverage report, run:

CI=true npm test:coverage

This creates a coverage subdirectory with the generated report. Open coverage/lcov-report/index.html in the browser to view it.

The CI=true environment variable prevents the tests from being run in interactive / watching mode.

See the Create React App documentation for more information about running tests.

Building the app for production

To build a production-optimized version of the React app to a build subdirectory, run:

npm run build

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.

Integration into Prometheus

To 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:

make build

This installs dependencies via npm, builds a production build of the React app, and then finally compiles in all web assets into the Prometheus binary.