In this example, we’ll walk through an example of enabling preview environments for a Python (Django) application that connects to a Postgres database. The sample repository can be found here.

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preview.yaml File Walkthrough

The preview.yaml file to define both a Postgres database and a web application is as follows:

version: v1
resources:
  - name: postgres
    source:
      name: postgresql
    config:
      postgresqlPassword: testing
  - name: web
    depends_on:
      - postgres
    source:
      name: web
    config:
      build:
        method: pack
        builder: heroku/buildpacks:20
      values:
        container:
          command: web
          port: 8000
          env:
            normal:
              POSTGRES_USERNAME: "{ .postgres.postgresqlUsername }"
              POSTGRES_PASSWORD: "{ .postgres.postgresqlPassword }"
  • postgres.source: by setting the source.name field to postgresql, Porter will look for a supported addon called postgresql.
  • postgres.config: the postgresql addon accepts the postgresqlPassword field to set the default Postgres password.
  • web.source: by setting the source.name field to web, Porter will deploy this resource as a web application.
  • web.depends_on: by setting the depends_on field to include postgres, Porter will wait for the postgres resource to be created before deploying the web application.
  • web.config.build: specifying the config.build.method field as pack instructs Porter to build this application using cloud-native buildpacks, and setting the builder to heroku/buildpacks:20 means that this buildpack will be used.
  • web.config.values: here, we set common configuration settings, such as the start command, the port that the application runs on, and environment variables for the application. Also, note that configuration references an output variable from the postgres resource.
Basic Web ApplicationDjango