Book Image

Docker Quick Start Guide

By : Earl Waud
Book Image

Docker Quick Start Guide

By: Earl Waud

Overview of this book

Docker is an open source software platform that helps you with creating, deploying, and running your applications using containers. This book is your ideal introduction to Docker and containerization. You will learn how to set up a Docker development environment on a Linux, Mac, or Windows workstation, and learn your way around all the commands to run and manage your Docker images and containers. You will explore the Dockerfile and learn how to build your own enterprise-grade Docker images. Then you will learn about Docker networks, Docker swarm, and Docker volumes, and how to use these features with Docker stacks in order to define, deploy, and maintain highly-scalable, fault-tolerant multi-container applications. Finally, you will learn how to leverage Docker with Jenkins to automate the building of Docker images and the deployment of Docker containers. By the end of this book, you will be well prepared when it comes to using Docker for your next project.
Table of Contents (10 chapters)

The HEALTHCHECK instruction

The HEALTHCHECK instruction, which is a fairly new addition to the Dockerfile, is used to define the command to run inside a container to test the container's application health. When a container has a HEALTHCHECK, it gets a special status variable. Initially, that variable will be set to starting. Any time a HEALTHCHECK is performed successfully, the status will be set to healthy. When a HEALTHCHECK is performed and fails, the fail count value will be incremented and then checked against a retries value. If the fail count equals or exceeds the retries value, the status is set to unhealthy. The syntax of the HEALTHCHECK instruction is as follows:

# HEALTHCHECK instruction syntax
HEALTHCHECK [OPTIONS] CMD command (check container health by running a command inside the container)
HEALTHCHECK NONE (disable any HEALTHCHECK inherited from the base image...