Continuous Deployment

Note! We are rewriting these parts to match Fly.io in the near future.

Continuous deployment refers to the process of deploying software to production whenever new code that passes the tests is added to the repository. There exists a range of ready github actions for deploying projects. For example, Deploy to Heroku action could be used to add continuous deployment to Heroku.

Let's continue with our continuous integration example and add continuous deployment to it. The github actions configuration file was as follows.

name: Run tests on project

on:
  push:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
      - name: Setup repo
        uses: actions/checkout@v2

      - name: Setup Deno
        uses: denoland/setup-deno@v1
        with:
          deno-version: "v1.42.2"

      - name: Run tests
        run: deno test --allow-all

Adding a new job

Let's first add a new job called deploy to the existing configuration file, also entering a new name Test and Deploy for the configuration. For the job deploy, we use needs-command to state that the new job requires that the previously configured job test passes. The deploy job uses the Deploy to Heroku action.

For the action, we need to configure an API key, our email, and the name of the application. For now, when these are not entered, the configuration looks as follows.

name: Test and Deploy

on:
  push:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
      - name: Setup repo
        uses: actions/checkout@v2

      - name: Setup Deno
        uses: denoland/setup-deno@v1
        with:
          deno-version: "v1.42.2"

      - name: Run tests
        run: deno test --allow-all

  deploy:
    runs-on: ubuntu-latest
    needs: test
    steps:
      - uses: actions/checkout@v2
      - uses: akhileshns/heroku-deploy@v3.12.12
        with:
          heroku_api_key: "my-very-secret-key"
          heroku_app_name: "my-app-name"
          heroku_email: "my-email-address"

Let's change the deno.yml file in GitHub to match the above one.

Not surprisingly, when we commit the above file to GitHub, nothing gets deployed.

Creating a project and extracting API key

Let's create a project to Heroku where the application could be deployed to. We set deno-ci-example as the name of the project and use https://github.com/chibat/heroku-buildpack-deno.git as the build pack. Furthermore, we use the following as the content for the Procfile.

web: deno run --allow-all app.js ${PORT}

And, as the application receives the port as a parameter, we adjust the app.js to start listening for requests if the application receives a port as a parameter.

import { Application, Router } from "https://deno.land/x/oak@v12.6.1/mod.ts";

const app = new Application();
const router = new Router();

const hello = ({ response }) => {
  response.body = "Hello world!";
};

router.get("/", hello);
app.use(router.routes());

if (Deno.args.length > 0) {
  const lastArgument = Deno.args[Deno.args.length - 1];
  app.listen({ port: Number(lastArgument) });
}

export { app };

For the deployment to work, we need an API key from Heroku. The API key is found in Account settings in Heroku; account settings are found at https://dashboard.heroku.com/account. The API Key can be found at the end of the page just before the Close Account option.

Click the Reveal button and copy the API Key for further use.

Adding Secrets

Now, go back to the project page on GitHub, and click Settings. Choose Secrets. This shows a page with the title Action secrets.

Now, click the button "New repository secret", and create a secret with the name HEROKU_API_KEY. Set the value of the secret to the API Key that you previously copied from Heroku.

Once the secret has been added, the Action secrets page should look something like the following one.

Proceed by adding two further secrets; (1) your email address to Heroku, and (2) the name of the application on Heroku. Label these secrets as HEROKU_EMAIL_ADDRESS and HEROKU_APPLICATION_NAME. At this point, there should be three secrets for the project.

Deploy configuration

Now that we have the secrets added to GitHub, we can add them to the deno.yml configuration file. Secrets are referred to using ${{secrets.SECRET_NAME}}, where SECRET_NAME refers to the name of a specific secret. For example, as we added our email address as a secret using the name HEROKU_EMAIL_ADDRESS, we can refer to it using ${{secrets.HEROKU_EMAIL_ADDRESS}} in the configuration file.

Below, we have added the three secrets to our configuration file.

name: Test and Deploy

on:
  push:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
      - name: Setup repo
        uses: actions/checkout@v2

      - name: Setup Deno
        uses: denoland/setup-deno@v1
        with:
          deno-version: "v1.42.2"

      - name: Run tests
        run: deno test --allow-all

  deploy:
    runs-on: ubuntu-latest
    needs: test
    steps:
      - uses: actions/checkout@v2
      - uses: akhileshns/heroku-deploy@v3.12.12
        with:
          heroku_api_key: ${{secrets.HEROKU_API_KEY}}
          heroku_app_name: ${{secrets.HEROKU_APPLICATION_NAME}}
          heroku_email: ${{secrets.HEROKU_EMAIL_ADDRESS}}

Now, whenever we add new content to GitHub, the application is also deployed to Heroku.