How to build a 12-Factor app rock

The following how-to guide provides instructions on managing and configuring rocks for 12-factor applications.

Include extra files in the OCI image

The following files are included in the image by default from the root of the project:

• app (does not apply to the go-framework)

• app.py (does not apply to the go-framework)

• migrate

• migrate.sh

• migrate.py (does not apply to the go-framework)

• static

• templates

To change this list, add the following snippet to the project file:

FlaskDjangoFastAPIGo

rockcraft.yaml

  parts:
    flask-framework/install-app:
      prime:
        - flask/app/.env
        - flask/app/app.py
        - flask/app/webapp
        - flask/app/templates
        - flask/app/static

Note the flask/app/ prefix that is required followed by the relative path to the project root.

Include additional debs in the OCI image

If your app requires debs – for example, to connect to a database – add the following snippet to the project file:

FlaskDjangoFastAPIGo

rockcraft.yaml

  parts:
    flask-framework/dependencies:
      stage-packages:
        # list required packages or slices for your flask application below.
        - libpq-dev

Update and deploy the OCI image

FlaskDjangoFastAPIGo

After making a change to your app:

1. Make sure that any new files will be included in the new OCI image.

2. Run rockcraft pack to create the new OCI image.

3. To upload the OCI image to the local Docker registry, run:

   rockcraft.skopeo --insecure-policy copy --dest-tls-verify=false \
   oci-archive:<path to rock file> \
   docker://localhost:32000/<rock name>:<rock version>
   

4. To deploy the new OCI image, run:

   juju refresh <app name> --path=<relative path to .charm file> \
   --resource flask-app-image=<localhost:32000/<rock name>:<rock version>>