When you generate a new Amber project, we include Dockerfile and docker-compose.yml files to simplify development. This is an alternative way of getting an Amber project up and running quickly and doesn't require installing a database.


The Dockerfile will have everything you need to build and run your amber project. This includes all the needed libraries, Nodejs, Crystal and Amber command line tools. It starts from the official crystallang/crystal:{version} docker image.

It will also add the project to the /app folder on the image so you can use this in production as well.


The docker-compose.yml file will allow you to easily get up and running. It includes the database, mailcatcher, migrate, app, and web containers.

The database container

This container is using an image based on the -d option you chose when you created the project. Right now, we support pg, mysql, sqlite

A db volume is also created so you can start and stop the containers but the data will still be available.

The mailcatcher container

Mail Catcher is a simple smtp server that will allow you to see the email that gets generated. You can access the user interface by hitting http://localhost:1080. If you generate mailers, it will configure the SMTP_URL to point to the mail catcher container.

The migrate container

This container will run the migrations using amber db migrate seed. It will wait for the database port to be available before running the migrations. This container will exit after completing the migrations.

The app container

This container will run amber watch on port 3000. You can access the application at http://localhost:3000. The external project directory is mapped to /app/local so as you make changes to your project and amber will watch for changes, recompile and re-launch the application.

The web container

This container will run npm install && npm run watch. This will compile your front-end assets and will watch for changes. You can see the webpack configuration in the config/webpack directory to see what assets are compiled.


You can launch the docker-compose environment by running:

docker-compose up

Once all the docker containers are launched, you can access the site using:

open http://localhost:3000

And you can access the mailcatcher at:

open http://localhost:1080

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