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Example apps

Ruby on Rails

This guide explains how to create and deploy a Ruby on Rails app. To run this example, follow these steps:

1. Install the unikraft CLI. You need a BuildKit builder. The easiest way to get one is via Docker. Alternatively, you can also directly set up and use BuildKit, see the quick start.

2. Clone the examples repository and cd into the examples/ruby3.2-rails/ directory:

   Code
   git clone https://github.com/unikraft-cloud/examples
   cd examples/ruby3.2-rails/

Make sure to log into Unikraft Cloud and pick a metro close to you. This guide uses fra (Frankfurt, 🇩🇪):

Code
unikraft login

When done, invoke the following command to deploy this app on Unikraft Cloud:

Code
unikraft build . --output <my-org>/ruby32-rails:latest
unikraft run --metro fra \
  -m 1G \
  -p 443:3000/tls+http \
  --scale-to-zero policy=idle,cooldown-time=1000,stateful=true \
  -e GEM_HOME=/usr/local/bundle \
  -e BUNDLE_APP_CONFIG=/usr/local/bundle \
  --image <my-org>/ruby32-rails:latest

The output shows the instance address and other details:

Code
metro:        fra
name:         ruby32-rails-apa93
uuid:         2f85b9db-94f8-45d2-8e38-ed9b56cb8695
state:        starting
image:        <my-org>/ruby32-rails
resources:
  memory:     1024MiB
  vcpus:      1
service:
  uuid:       42265dab-df44-6d66-0075-fc07455178c8
  name:       aged-waterfall-qraz0s7d
  domains:
  - fqdn:     aged-waterfall-qraz0s7d.fra.unikraft.app
networks:
- uuid:       7ae3414b-1d87-c831-d26a-506a4cf9ac71
  private-ip: 10.0.3.3
  mac:        12:b0:39:3e:b5:36
timestamps:
  created:    just now

In this case, the instance name is ruby32-rails-apa93 and the address is https://aged-waterfall-qraz0s7d.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the Python-based HTTP web server:

Code
curl https://aged-waterfall-qraz0s7d.fra.unikraft.app/hello

Code
[...]
  <body>
    <h1>Hello World</h1>
Hello, World!

  </body>
[...]

You can list information about the instance by running:

Code
unikraft instances list

Code
METRO  NAME                STATE    IMAGE                  ARGS  MEMORY  VCPUS  FQDN                                      CREATED
fra    ruby32-rails-apa93  running  <my-org>/ruby32-rails        1.0GiB  1      aged-waterfall-qraz0s7d.fra.unikraft.app  2 minutes ago

When done, you can remove the instance:

Code
unikraft instances delete ruby32-rails-apa93

Customize your app

To customize the app, update the files in the repository, listed below:

• app/ and config/: the contents to update the Rails setup
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem

The app/ and config/ directories contain files that are to overwrite generated Rails files:

Code
tree app/ config/

Code
app/
|-- controllers/
|   `-- hello_controller.rb
`-- views/
    `-- hello/
        `-- index.html.erb
config/
|-- environments/
|   `-- development.rb
`-- routes.rb

These files add the configuration (controller, view, route) to print the Hello, World! message in Rails. They overwrite the generated Rails configuration to provide the app setup. Update these files, and other files, with required contents for your own app.

Lines in the Kraftfile have the following roles:

• spec: v0.7: The current Kraftfile specification version is 0.7.

• runtime: base-compat:latest: The runtime kernel to use is the base compatibility kernel.

• rootfs: Build the app root filesystem. source: ./Dockerfile means the filesystem is built using the Dockerfile. format: erofs means the filesystem type is EROFS.

• cmd: ["/usr/bin/ruby", "/app/bin/rails", "server", "-b", "0.0.0.0"]: Use /usr/bin/ruby /app/bin/rails server -b 0.0.0.0 as the starting command of the instance.

Lines in the Dockerfile have the following roles:

• The RUN lines install Rails and generate the default app setup for a hello app.

• COPY . /app/: Copies the local files (from app/ and config/) to the app, overwriting generated contents to provide the user-specified app.

• FROM scratch: Build the filesystem from the scratch container image, to create a base image.

• COPY --from=build /app /app: Copy the app directory to the filesystem.

The following options are available for customizing the app:

• If you only update the implementation in the app/ or config/ directories, or adding new directories or files to overwrite Rails generated files, you don't need to make any other changes.

• If changing the app name, change the hello name in RUN rails generate controller hello to a new one. The file names in the app/ and config/ directories have to be similarly updated.

• More extensive changes may require extending the Dockerfile (see Dockerfile syntax reference).

Learn more

Use the --help option for detailed information on using Unikraft Cloud:

Code
unikraft --help

Or visit the CLI Reference.