Docker Learning Note (iv)

E.Y.

3 min readAug 8, 2020

This is a series blogs about Docker and Kubernetes — This is the 4th blog following up to my last one.

In last blog, we will focus on Docker compose file.

Docker compose acts like a CLI tool that helps to start up multiple docker containers at the same time; it helps to specify what images are required, what ports they need to expose, and so on. Common commands exclude:

- docker run my_image
docker-compose up- docker build. && docker run myimage
docker-compose up --build$docker-compose up - launch in the background 
docker-compose up -d- stop contianers
docker-compose down- look for container status (from root directory with the yaml file)
docker-compose ps

Replace Dockerfile with docker-compose.yml

A common use case for multiple files is changing a development Compose app for a production-like environment (which may be production, staging or CI). To support these differences, you can split your Compose configuration into a few different files. In the example we have web and tests for dev environment.

version: “3” //version 3 of the tool
services:
  web:
    stdin_open: true 
    build:
      context: .  //the content to build the Dockerfile 
      dockerfile: Dockerfile.dev //get the name more clear
    ports:
      - “3000:3000”
    volumes: //mapping local file to docker container == setting up reference to the local file
      - /app/node_modules //make this reserved in container, so this dir won't be overwritten by the copy command below
      - .:/app. //map the parent directory /app in the container
  tests: //2nd service solely to run the test live
    stdin_open: true
    build:
      context: .
      dockerfile: Dockerfile.dev
    volumes: 
      - /app/node_modules
      - .:/app
    command: ["npm", "run", "test"] //override original npm run start command

As reference, the Dockerfile.dev that is mentioned above:

Dockerfile.dev
=====================FROM node:alpine
WORKDIR '/app'
COPY package.json .
RUN npm install
COPY . .
CMD ["npm", "run", "start"]

A more complex but common configure with client, server, worker and nginx:

//docker-compose.yml
version: “3”services:
  postgres:
    image: “postgres:latest”
    environment:
      - POSTGRES_PASSWORD=postgres_password
  redis:
    image: “redis:latest”  server:
    build:
      dockerfile: Dockerfile.dev
      context: ./server
    volumes:
      - /app/node_modules
      - ./server:/app
    environment: //set up envName=value
      - REDIS_HOST=redis
      - REDIS_PORT=6379
      - PGHOST=postgres
      - PGUSER=postgres
      - PGDATABASE=postgres
      - PGPASSWORD=postgres_password
      - PGPORT=5432  client:
    stdin_open: true
    build:
     dockerfile: Dockerfile.dev
     context: ./client
    volumes:
     - /app/node_modules
     - ./client:/app  worker:
    build:
     dockerfile: Dockerfile.dev
     context: ./worker
    volumes:
     - /app/node_modules
     - ./worker:/app  nginx:
   restart: always
   build:
    dockerfile: Dockerfile.dev
    context: ./nginx
   ports:
    - "3050:80"

And the Dockerfiles mentioned above are:

//server 
FROM node:alpine
WORKDIR '/app'
COPY ./package.json ./
RUN npm install
COPY . .
CMD ["npm", "run", "dev"]//worker
FROM node:alpine
WORKDIR '/app'
COPY ./package.json ./
RUN npm install
COPY . .
CMD ["npm", "run", "dev"]//nginx
FROM nginx
COPY ./default.conf /etc/nginx/conf.d/default.conf//client
FROM node:alpine
WORKDIR '/app'
COPY ./package.json ./
RUN npm install
COPY . .
CMD ["npm", "run", "start"]

That’s so much of it. Happy Reading!

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Docker Learning Note (iv)

Replace Dockerfile with docker-compose.yml

Written by E.Y.