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Docker Orchestration
Docker Orchestration

Docker Orchestration: A concise, fast-paced guide to orchestrating and deploying scalable services with Docker

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Profile Icon Arbezzano Profile Icon Randall Smith
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Paperback Jan 2017 284 pages 1st Edition
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Profile Icon Arbezzano Profile Icon Randall Smith
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Paperback Jan 2017 284 pages 1st Edition
eBook
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Paperback
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Docker Orchestration

Chapter 2. Building Multi-Container Applications with Docker Compose

Modern applications have a lot of moving parts. A web application almost always uses a database such as MySQL or MongoDB to store data. There may be a load balancer or SSL proxy. Often there are tasks scheduled to run regularly that perform routine maintenance or backups. On a traditional server, these tasks might all be installed on a single server or spread across numerous hosts. The challenge faced by system administrators is how are all these parts deployed consistently and reliably?

Rather than having a single container that does everything, you can split your application into smaller chunks. Each container has a specific task and does only that task. For example, you might have one image that is a Perl-based web application; a second that runs MySQL; a third that runs HAProxy to load balance and provide SSL termination for the Perl application. Each separate container can be run, upgraded, and tested independent...

Building an image with Docker Engine

They say the longest journey begins with a single step. In this case, an application begins with a single image. More often than not, existing images will not be perfect fits. This will certainly be the case if you are deploying your own services.

It all starts with a Dockerfile. This file provides detailed instructions to Docker for building an image. There are a lot of things that can be done in a Dockerfile. Specific operating system packages or language libraries can be installed; configuration files can be put into place; and a default command can be set. It is best to base a new image for an application off an official image, when possible. For example, an application written in Ruby should be based off of the official ruby image. A full reference of the Dockerfile directives can be found at https://docs.docker.com/engine/reference/builder/ .

Building from a Dockerfile

Back in Chapter 1 , Getting Started with Docker Orchestration, we started with...

Installing Docker Compose

Once your images are built, you need to tell Docker how to run them. Docker Engine is limited in allowing you to define how containers work together. The Docker project provides a solution called Docker Compose. Docker Compose is a great tool for testing out deployments, defining how containers will interact or what external storage they need, or even as a lightweight orchestration tool.

Installing Docker Compose is easy. For Windows and OS X users, docker-compose installs as part of the Docker Toolbox and Docker for Mac and Windows. For Linux users, docker-compose can be downloaded from the Docker repository on GitHub. The following command from the Docker Compose documentation shows you how:

# curl -L https://github.com/docker/compose/releases/download/1.8.0  /docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose
  • As shown, the curl command must be run as root in order to have the permissions to...

Writing a Docker Compose file

A Docker Compose file defines everything about an application. The services, volumes, networks, and dependencies can all be defined in one place. The configuration can be used locally to stand up a development environment, plugged into an existing continuous integration or continuous deployment system, or even used on a server to start production services. Later chapters will show better ways to manage running services.

Docker Compose looks for a file named docker-compose.yml in the current directory. An alternate file can be specified with the -f option. The file is formatted in YAML so it can be edited in any text editor.

Let's start with a very simple compose file that starts a single nginx container that listens on port 80. This is an analogous container started with docker run -p 80:80 nginx. The value for image can be any image on your server or on the registry just like in the docker run command:

version: '2' 
services: 
  web: 
    image...

Multi-container applications

The example in the previous section was fun but did not really gain us anything over using the docker command. Most Internet applications have multiple pieces. The most common example is a web application that loads data from a database.

In ch02/web-db of the docker-orchestration-examples repository there is a very simple application that loads a list of authors and books from MySQL and displays them on a web page. Here is a docker-compose.yml that defines the application:

version: '2' 
 
services: 
  web: 
    image: web-db:0.1 
    build: . 
    ports: 
      - 80:5000 
    env_file: 
      - db.env 
    entrypoint: ./start.pl --init --command shotgun 
  db: 
    image: mysql:5.7 
    env_file: 
      - db.env 

The first thing that you should notice is that there are two services defined. The first, web, is the web application. The second, db, is a MySQL container. Let's look at them one at a time.

The build key tells docker-compose that this service...

Building an image with Docker Engine


They say the longest journey begins with a single step. In this case, an application begins with a single image. More often than not, existing images will not be perfect fits. This will certainly be the case if you are deploying your own services.

It all starts with a Dockerfile. This file provides detailed instructions to Docker for building an image. There are a lot of things that can be done in a Dockerfile. Specific operating system packages or language libraries can be installed; configuration files can be put into place; and a default command can be set. It is best to base a new image for an application off an official image, when possible. For example, an application written in Ruby should be based off of the official ruby image. A full reference of the Dockerfile directives can be found at https://docs.docker.com/engine/reference/builder/ .

Building from a Dockerfile

Back in Chapter 1 , Getting Started with Docker Orchestration, we started with...

Installing Docker Compose


Once your images are built, you need to tell Docker how to run them. Docker Engine is limited in allowing you to define how containers work together. The Docker project provides a solution called Docker Compose. Docker Compose is a great tool for testing out deployments, defining how containers will interact or what external storage they need, or even as a lightweight orchestration tool.

Installing Docker Compose is easy. For Windows and OS X users, docker-compose installs as part of the Docker Toolbox and Docker for Mac and Windows. For Linux users, docker-compose can be downloaded from the Docker repository on GitHub. The following command from the Docker Compose documentation shows you how:

# curl -L https://github.com/docker/compose/releases/download/1.8.0  /docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose
  • As shown, the curl command must be run as root in order to have the permissions to write the...

Writing a Docker Compose file


A Docker Compose file defines everything about an application. The services, volumes, networks, and dependencies can all be defined in one place. The configuration can be used locally to stand up a development environment, plugged into an existing continuous integration or continuous deployment system, or even used on a server to start production services. Later chapters will show better ways to manage running services.

Docker Compose looks for a file named docker-compose.yml in the current directory. An alternate file can be specified with the -f option. The file is formatted in YAML so it can be edited in any text editor.

Let's start with a very simple compose file that starts a single nginx container that listens on port 80. This is an analogous container started with docker run -p 80:80 nginx. The value for image can be any image on your server or on the registry just like in the docker run command:

version: '2' 
services: 
  web: 
    image...

Multi-container applications


The example in the previous section was fun but did not really gain us anything over using the docker command. Most Internet applications have multiple pieces. The most common example is a web application that loads data from a database.

In ch02/web-db of the docker-orchestration-examples repository there is a very simple application that loads a list of authors and books from MySQL and displays them on a web page. Here is a docker-compose.yml that defines the application:

version: '2' 
 
services: 
  web: 
    image: web-db:0.1 
    build: . 
    ports: 
      - 80:5000 
    env_file: 
      - db.env 
    entrypoint: ./start.pl --init --command shotgun 
  db: 
    image: mysql:5.7 
    env_file: 
      - db.env 

The first thing that you should notice is that there are two services defined. The first, web, is the web application. The second, db, is a MySQL container. Let's look at them one...

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Key benefits

  • - Explore the new features added to the core Docker Engine to make multi-container orchestration easy
  • - Leverage tools such as Docker Machine, Swarm, Compose, and third-party tools such as Kubernetes, Mesosphere, and CoreOS to orchestrate containers
  • - Use Docker Compose with Swarm and apply rolling updates for zero downtime deployments

Description

Docker orchestration is what you need when transitioning from deploying containers individually on a single host to deploying complex multi-container apps on many machines. This book covers the new orchestration features of Docker 1.12 and helps you efficiently build, test, and deploy your application using Docker. You will be shown how to build multi-container applications using Docker Compose. You will also be introduced to the building blocks for multi-host Docker clusters such as registry, overlay networks, and shared storage using practical examples. This book gives an overview of core tools such as Docker Machine, Swarm, and Compose which will enhance your orchestration skills. You’ll learn how to set up a swarm using the decentralized building block. Next, you’ll be shown how to make the most out of the in-built orchestration feature of Docker engine and you’ll use third-party tools such as Kubernetes, Mesosphere, and CoreOS to orchestrate your existing process. Finally, you will learn to deploy cluster hosts on cloud services and automate your infrastructure.

Who is this book for?

This book is aimed at Sysadmins and DevOps engineers who know what Docker does and are now looking to manage multiple containers on multiple hosts using the orchestration feature.

What you will learn

  • - Build scalable, reliable services with Docker
  • - See how to manage a service in Docker using Docker Swarm, Kubernetes, and Mesosphere
  • - Discover simpler orchestration tools such as CoreOS/Fleet and Rancher Cattle
  • - Understand cluster-wide logging, system monitoring, and troubleshooting
  • - Build, test, and deploy containers using Continuous Integration
  • - Deploy cluster hosts on cloud services and automate your infrastructure

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Jan 24, 2017
Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781787122123
Vendor :
Docker
Languages :
Tools :

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Product Details

Publication date : Jan 24, 2017
Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781787122123
Vendor :
Docker
Languages :
Tools :

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Table of Contents

10 Chapters
1. Getting Started with Docker Orchestration Chevron down icon Chevron up icon
2. Building Multi-Container Applications with Docker Compose Chevron down icon Chevron up icon
3. Cluster Building Blocks – Registry, Overlay Networks, and Shared Storage Chevron down icon Chevron up icon
4. Orchestration with Docker Swarm Chevron down icon Chevron up icon
5. Deploying and Managing Services with Kubernetes Chevron down icon Chevron up icon
6. Working with Mesosphere Chevron down icon Chevron up icon
7. Using Simpler Orchestration Tools – Fleet and Cattle Chevron down icon Chevron up icon
8. Monitoring Your Cluster Chevron down icon Chevron up icon
9. Using Continuous Integration to Build, Test, and Deploy Containers Chevron down icon Chevron up icon
10. Why Stop at Containers? Automating Your Infrastructure Chevron down icon Chevron up icon
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