Using Docker

Chapter 6. Creating a Simple Web App

In this chapter, we’ll turn our “Hello World!” program into a simple web app that generates a unique image for users when they enter some text. These images are sometimes known as identicons and can be used to identify users by providing a unique image generated from their username or IP address. At the end of this chapter, you’ll have a basic working application that we will extend and play with in the following chapters. By creating this application, we’ll see how to compose Docker containers to build a fully functioning system and how this naturally leads to a microservice approach.

Identicons

Identicons are images that are automatically generated from a value, normally the hash of an IP address or username. They provide a visual representation of the object so that it can be readily identified. Use cases include providing identifying images for users on a website by hashing their username or IP address and providing automatic favicons for websites.

They were originally developed by Don Park in early 2007 to identify commenters on his blog; the code is still available on his GitHub project page.

Since then, there have been several further implementations with different graphical styles. Two large adopters of identicons are Stack Overflow and GitHub, both of which use them for users who haven’t set their own. Stack Overflow uses ones generated by the Gravatar service, which in turn uses the WP_Identicon project, among others. GitHub generates ...