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Week 1 — App Containerization

References

Good Article for Debugging Connection Refused https://pythonspeed.com/articles/docker-connection-refused/

VSCode Docker Extension

Docker for VSCode makes it easy to work with Docker

https://code.visualstudio.com/docs/containers/overview

Gitpod is preinstalled with theis extension

Containerize Backend

Run Python

cd backend-flask
export FRONTEND_URL="*"
export BACKEND_URL="*"
python3 -m flask run --host=0.0.0.0 --port=4567
cd ..
  • make sure to unlock the port on the port tab
  • open the link for 4567 in your browser
  • append to the url to /api/activities/home
  • you should get back json

Add Dockerfile

Create a file here: backend-flask/Dockerfile

FROM python:3.10-slim-buster

WORKDIR /backend-flask

COPY requirements.txt requirements.txt
RUN pip3 install -r requirements.txt

COPY . .

ENV FLASK_ENV=development

EXPOSE ${PORT}
CMD [ "python3", "-m" , "flask", "run", "--host=0.0.0.0", "--port=4567"]

Build Container

docker build -t  backend-flask ./backend-flask

Run Container

Run

docker run --rm -p 4567:4567 -it backend-flask
FRONTEND_URL="*" BACKEND_URL="*" docker run --rm -p 4567:4567 -it backend-flask
export FRONTEND_URL="*"
export BACKEND_URL="*"
docker run --rm -p 4567:4567 -it -e FRONTEND_URL='*' -e BACKEND_URL='*' backend-flask
docker run --rm -p 4567:4567 -it  -e FRONTEND_URL -e BACKEND_URL backend-flask
unset FRONTEND_URL="*"
unset BACKEND_URL="*"

Run in background

docker container run --rm -p 4567:4567 -d backend-flask

Return the container id into an Env Vat

CONTAINER_ID=$(docker run --rm -p 4567:4567 -d backend-flask)

docker container run is idiomatic, docker run is legacy syntax but is commonly used.

Get Container Images or Running Container Ids

docker ps
docker images

Send Curl to Test Server

curl -X GET http://localhost:4567/api/activities/home -H "Accept: application/json" -H "Content-Type: application/json"

Check Container Logs

docker logs CONTAINER_ID -f
docker logs backend-flask -f
docker logs $CONTAINER_ID -f

Debugging adjacent containers with other containers

docker run --rm -it curlimages/curl "-X GET http://localhost:4567/api/activities/home -H \"Accept: application/json\" -H \"Content-Type: application/json\""

busybosy is often used for debugging since it install a bunch of thing

docker run --rm -it busybosy

Gain Access to a Container

docker exec CONTAINER_ID -it /bin/bash

You can just right click a container and see logs in VSCode with Docker extension

Delete an Image

docker image rm backend-flask --force

docker rmi backend-flask is the legacy syntax, you might see this is old docker tutorials and articles.

There are some cases where you need to use the --force

Overriding Ports

FLASK_ENV=production PORT=8080 docker run -p 4567:4567 -it backend-flask

Look at Dockerfile to see how ${PORT} is interpolated

Containerize Frontend

Run NPM Install

We have to run NPM Install before building the container since it needs to copy the contents of node_modules

cd frontend-react-js
npm i

Create Docker File

Create a file here: frontend-react-js/Dockerfile

FROM node:16.18

ENV PORT=3000

COPY . /frontend-react-js
WORKDIR /frontend-react-js
RUN npm install
EXPOSE ${PORT}
CMD ["npm", "start"]

Build Container

docker build -t frontend-react-js ./frontend-react-js

Run Container

docker run -p 3000:3000 -d frontend-react-js

Multiple Containers

Create a docker-compose file

Create docker-compose.yml at the root of your project.

version: "3.8"
services:
  backend-flask:
    environment:
      FRONTEND_URL: "https://3000-${GITPOD_WORKSPACE_ID}.${GITPOD_WORKSPACE_CLUSTER_HOST}"
      BACKEND_URL: "https://4567-${GITPOD_WORKSPACE_ID}.${GITPOD_WORKSPACE_CLUSTER_HOST}"
    build: ./backend-flask
    ports:
      - "4567:4567"
    volumes:
      - ./backend-flask:/backend-flask
  frontend-react-js:
    environment:
      REACT_APP_BACKEND_URL: "https://4567-${GITPOD_WORKSPACE_ID}.${GITPOD_WORKSPACE_CLUSTER_HOST}"
    build: ./frontend-react-js
    ports:
      - "3000:3000"
    volumes:
      - ./frontend-react-js:/frontend-react-js

# the name flag is a hack to change the default prepend folder
# name when outputting the image names
networks: 
  internal-network:
    driver: bridge
    name: cruddur

Adding DynamoDB Local and Postgres

We are going to use Postgres and DynamoDB local in future labs We can bring them in as containers and reference them externally

Lets integrate the following into our existing docker compose file:

Postgres

services:
  db:
    image: postgres:13-alpine
    restart: always
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=password
    ports:
      - '5432:5432'
    volumes: 
      - db:/var/lib/postgresql/data
volumes:
  db:
    driver: local

To install the postgres client into Gitpod

  - name: postgres
    init: |
      curl -fsSL https://www.postgresql.org/media/keys/ACCC4CF8.asc|sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/postgresql.gpg
      echo "deb http://apt.postgresql.org/pub/repos/apt/ `lsb_release -cs`-pgdg main" |sudo tee  /etc/apt/sources.list.d/pgdg.list
      sudo apt update
      sudo apt install -y postgresql-client-13 libpq-dev

DynamoDB Local

services:
  dynamodb-local:
    # https://stackoverflow.com/questions/67533058/persist-local-dynamodb-data-in-volumes-lack-permission-unable-to-open-databa
    # We needed to add user:root to get this working.
    user: root
    command: "-jar DynamoDBLocal.jar -sharedDb -dbPath ./data"
    image: "amazon/dynamodb-local:latest"
    container_name: dynamodb-local
    ports:
      - "8000:8000"
    volumes:
      - "./docker/dynamodb:/home/dynamodblocal/data"
    working_dir: /home/dynamodblocal

Example of using DynamoDB local https://github.com/100DaysOfCloud/challenge-dynamodb-local

Volumes

directory volume mapping

volumes: 
- "./docker/dynamodb:/home/dynamodblocal/data"

named volume mapping

volumes: 
  - db:/var/lib/postgresql/data

volumes:
  db:
    driver: local