Working with Containers: Docker & Docker Compose/

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Automating Deployments Using Docker Stack

Automating Deployments Using Docker Stack

A docker-compose alternative for swarm cluster

We'll cover the following...

In this lesson, we will automate all the steps we took to create and deploy our app using services.

Clone the project using git clone https://github.com/venky8283/Docker.git
Type git checkout fc0a9af7f7fb2c8d61e4777befdbf451568cf578 to get the exact code used in this lesson.

We did the same thing while working with docker-compose. In docker-compose, we created a docker-compose file and automated all the steps in it.

We will modify the same docker-compose file to run with docker-swarm because Compose and Docker stack are similar on some level.

Let’s list all the steps we need to automate as follows:

  • Pull the Flask_app v3.0 image from Docker Hub

  • Increase the number of replicas of the Flask app to three

  • Create a database service

  • Establish communication between services using the network

  • Create a visualizer service to monitor the swarm

Docker stack implementation

Docker stack is a bundle of services. When you want to deploy a set of services to a machine, instead of creating each service separately, Docker stack allows users to deploy the full-stack of the services at once.

Let’s see changes in our docker-compose file below.

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version: '3.8'
services:
  web:
    
    image: venky8283/flask_app:3.0
    # Mapping of container port to host
    
    ports:
      - "5000:5000"
    # Mount volume 
    volumes:
      - "./:/code"
    
    networks:
      - app
    
    deploy:
      replicas: 3
    
  database:
    # image to fetch from docker hub
    image: mysql/mysql-server:5.7
    # Environment variables for startup script
    # container will use these variables
    # to start the container with these defined variables. 
    env_file:
      - ./.env
    # Mount init.sql file to automatically run 
    # and create tables for us.
    # everything in docker-entrypoint-initdb.d folder
    # is executed as soon as container is up nd running.
    volumes:
      - "./db/init.sql:/docker-entrypoint-initdb.d/init.sql"
    
    deploy:
      replicas: 2
    networks:
      - app
  
  viz:
    # Visualizer image for swarm cluster.
    image: dockersamples/visualizer
    # Mapping container ports to host port
    ports: 
      - "8080:8080"
    # Mounting docker socket to container.
    
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    
    networks:
      - app
    
  
networks:
  app:

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