lab-2-answer-key.md

Lab 2 - Creating Docker and Kubernetes configurations

Overview

In this lab we will look through the Dockerfile and Kubernetes configuration files, as well as the health check that will be used on the pods.

Procedure

Step 1 - Examine Dockerfile

A few lines of note:

1. We set the application's port: ENV PORT 3000

2. We build the backend of the application: RUN bundle install

3. We build the frontend of the application:

RUN yarn upgrade webpack@^4.0.0 && bundle exec rake assets:precompile

4. We start the Puma server at the end:

CMD ["bundle", "exec", "puma", "-C", "config/puma.rb"]

Step 2 - Examine app deployment yaml

1. We select the type of resource: kind: "Deployment"
2. We specify the name of the app: name: "link-app"
3. We specify the container image: image: link-container
4. Because the image will be local, we add imagePullPolicy: Never
5. We configure the requested resources in the resources section.
6. We provide values for environment variables:

        env:
        - name: "DATABASE_URL"
          value: "postgresql://postgres@172.16.100.20:5432/link"
        - name: "REDIS_URL"
          value: "redis://172.16.100.20:6379/15"

Step 3 - Examine app service yaml

1. We select type of resource: kind: "Service"
2. We specify the name of the app: name: "link-app"
3. We specify the port mapping for incoming requests:

    port: 3000
    targetPort: 3000
    nodePort: 30000

Step 4 - Examine sidekiq deployment yaml

This file is very similar to the app deployment yaml. It includes this section to indicate what app deploymenty it is connected to:

  selector:
    matchLabels:
      app: "link-app"

Step 5 - Examine health check

You can find the health check under lib/health_check.rb. It has been implemented as rack middleware for the purposes of this workshop. You can find the health check configured under each different environment in config/environments.