Running development server with create-react-app inside of a docker container

If your changes are not being picked up, it is probably a problem with the file watching mechanism. A workaround for this issue is to configure polling. You can do that globally as explained by @Javascriptonian, but you can do this also locally via the webpack configuration. This has the benefit of specifying ignored folders (e.g. node_modules) which slow down the watching process (and lead to high CPU usage) when using polling.

In your webpack configuration, add the following configuration:

devServer: {
  watchOptions: {
    poll: true, // or use an integer for a check every x milliseconds, e.g. poll: 1000
    ignored: /node_modules/ // otherwise it takes a lot of time to refresh
  }
}

source: documentation webpack watchOptions

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If you are having the same issue with nodemon in a back-end Node.js project, you can use the --legacy-watch flag (short -L) which starts polling too.

npm exec nodemon -- --legacy-watch --watch src src/main.js

or in package.json:

"scripts": {
  "serve": "nodemon --legacy-watch --watch src src/main.js"
}

documentation: nodemon legacy watch

Polling, suggested in the other answer, will cause much higher CPU usage and drain your battery quickly. You should not need CHOKIDAR_USEPOLLING=true since file system events should be propagated to the container. Since recently this should work even if your host machine runs Windows: https://docs.docker.com/docker-for-windows/release-notes/#docker-desktop-community-2200 (search for "inotify").

However, when using Docker for Mac, this mechanism seems to be failing sometimes: https://github.com/docker/for-mac/issues/2417#issuecomment-462432314

Restarting the Docker daemon helps in my case.

Actually, I found an answer here. Apparently create-react-app uses chokidar to watch file changes, and it has a flag CHOKIDAR_USEPOLLING to use polling to watch for file changes instead. So CHOKIDAR_USEPOLLING=true npm start should fix the problem. As for me, I set CHOKIDAR_USEPOLLING=true in my environment variable for the docker container and just started the container.