Implementing Automatic Updates with Compose Watch and Adding Data Persistence

Now, run the following `docker compose up` command to start your application. ```console $ docker compose up --build ``` In Ruby on Rails, `db:migrate` is a Rake task that is used to run migrations on the database. Migrations are a way to alter the structure of your database schema over time in a consistent and easy way. ```console $ docker exec -it docker-ruby-on-rails-web-1 rake db:migrate RAILS_ENV=test ``` You will see a similar message like this: `console == 20240710193146 CreateWhales: migrating ===================================== -- create_table(:whales) -> 0.0126s == 20240710193146 CreateWhales: migrated (0.0127s) ============================ ` Refresh <http://localhost:3000> in your browser and add the whales. Press `ctrl+c` in the terminal to stop your application and run `docker compose up` again, the whales are being persisted. ## Automatically update services Use Compose Watch to automatically update your running Compose services as you edit and save your code. For more details about Compose Watch, see [Use Compose Watch](/manuals/compose/how-tos/file-watch.md). Open your `compose.yaml` file in an IDE or text editor and then add the Compose Watch instructions. The following is the updated `compose.yaml` file. ```yaml {hl_lines="13-16"} services: web: build: . command: bundle exec rails s -b '0.0.0.0' ports: - "3000:3000" depends_on: - db environment: - RAILS_ENV=test env_file: "webapp.env" develop: watch: - action: rebuild path: . db: image: postgres:latest secrets: - db-password environment: - POSTGRES_PASSWORD_FILE=/run/secrets/db-password volumes: - postgres_data:/var/lib/postgresql/data volumes: postgres_data: secrets: db-password: file: db/password.txt ``` Run the following command to run your application with Compose Watch. ```console $ docker compose watch ``` Any changes to the application's source files on your local machine will now be immediately reflected in the running container. Open `docker-ruby-on-rails/app/views/whales/index.html.erb` in an IDE or text editor and update the `Whales` string by adding an exclamation mark. ```diff - <h1>Whales</h1> + <h1>Whales!</h1> ``` Save the changes to `index.html.erb` and then wait a few seconds for the application to rebuild. Go to the application again and verify that the updated text appears. Press `ctrl+c` in the terminal to stop your application. ## Summary In this section, you took a look at setting up your Compose file to add a local database and persist data. You also learned how to use Compose Watch to automatically rebuild and run your container when you update your code. Related information: - [Compose file reference](/reference/compose-file/) - [Compose file watch](/manuals/compose/how-tos/file-watch.md) - [Multi-stage builds](/manuals/build/building/multi-stage.md) ## Next steps In the next section, you'll learn how you can locally test and debug your workloads on Kubernetes before deploying.

This section details how to implement automatic updates to a running Dockerized Rails application using Compose Watch. It starts by modifying the `compose.yaml` file to include Compose Watch instructions, specifically setting up a watch on the application's source files. It then guides on how to run the application with `docker compose watch` and demonstrates the automatic rebuilding and updating of the container upon changes to source files, like modifying the `index.html.erb` file. The section also summarizes the benefits of using Compose for local database setup and data persistence, as well as the automatic rebuilding of containers. Finally, it provides links to relevant documentation and introduces the next steps involving local testing and debugging on Kubernetes.