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Mastering Elixir
Mastering Elixir

Mastering Elixir: Build and scale concurrent, distributed, and fault-tolerant applications

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Mastering Elixir

Innards of an Elixir Project

After looking at the building blocks in the past chapter, we will now explore the fundamental aspects of any Elixir project. There are a few rules that need to be followed, but fortunately every one of them is simple to adopt and contributes to an understandable project structure. An application that doesn't get in the way of the evolution and maintenance tasks during all its years in production is a joy for the people who work with it, and this is exactly what we aim for.

We will start by learning what an Elixir application is and how we can structure an Elixir project, along with some of the existing good practices that you can leverage. We will introduce Umbrella applications and how they can help you to define more rigid boundaries between your project's components. When creating our umbrella project, we will use some common...

Elixir applications

Elixir inherits a lot of concepts from Erlang/OTP, and the application's behaviour is one of those concepts. For the Erlang VM, an application is a component that can be started and stopped as a single unit, and is described by an .app file (for example, hello_world.app) that defines, among other things, the Application Module Callback. This is a module that needs to implement a  start/2 function that's responsible for kickstarting the application, usually by spawning its top-level supervisor (in the next chapter, you'll learn all about supervisors). In a way, you can think about the start/2 function as the common main entry point on applications developed with other programming languages.

Because we're using Elixir, we don't need to explicitly specify the .app file. The Elixir compiler...

Elixir project structure

In the previous section, we created a sample project with Mix, but we didn't explore it thoroughly. Despite not enforcing a rigid structure and looking really simple, the Elixir project structure sets the baseline of every project, enabling you to get up to speed when facing a new codebase.

Let's create a simpler project, using mix new simple_project to generate the initial folder structure for us. Besides creating the .gitignore and README.md files, it also created the mix.exs file and three separate folders: config, lib and test. Take a look at this:

$ mix new simple_project
* creating README.md
* creating .gitignore
* creating mix.exs
* creating config
* creating config/config.exs
* creating lib
* creating lib/simple_project.ex
* creating test
* creating test/test_helper.exs
* creating test/simple_project_test.exs

Your Mix project...

Umbrella projects

In the previous section, we started by defining and creating a sample Elixir application with Mix. By using the application's behaviour, we were able to start and stop it as a unit, and other applications could depend on it by pointing to this application in their dependencies.

As time passes, and your application gets bigger, you start thinking about how to divide it into smaller independent components with well-defined responsibilities. At this point, will you create a project from scratch for your recently extracted logic and add it as a dependency? Probably not, since, for now, those extracted components only make sense in the context of your original application.

An umbrella project helps you in this situation, because it allows you to have more than one application under the same Elixir project. Mix lets you achieve this by placing your individual...

ElixirDrip – our showcase application

To clearly illustrate how you may incorporate the concepts and strategies in this book, we will develop a fully fledged web application named ElixirDrip, which was kick-started by the umbrella project we have just created.

ElixirDrip aims to be a fast and scalable web storage service, allowing the user to easily store and share their files living on the cloud. Our users will be able to upload files to their cloud storage and then share those files with other ElixirDrip users.

We will be adding features to the ElixirDrip umbrella application as we progress, taking it closer to our final goal with each chapter. The most important features of our application will be tackled in specific chapters throughout this book. Consider the following:

  • The design and implementation of our domain model will be analyzed in Chapter 7Persisting...

Adopting a consistent coding style

During your project inception, one of the most important steps is deciding on how to structure your project. The choices made here will, in the long term, affect how you maintain and evolve your application. The usage of static code analysis tools also contribute to the ease of maintenance of your project, letting you catch bugs, syntax errors and weird code style as soon as possible.

Here, we'll configure Credo to analyze our code, looking for possible refactors, common mistakes and inconsistencies and then use the Elixir 1.6 formatter to format all the code of our application.

We do not want to run our static analysis tools in production, so we will only add Credo as a dependency for the dev and test environments. We'll also make sure that Credo stays put when we run our project, by setting its runtime option as false...

Summary

In this chapter, we looked at an Elixir project from different angles. Accompanied by the versatile Mix tool that comes with Elixir, we ended the chapter by kick-starting our ElixirDrip umbrella project with two umbrella applications. These were the key ideas we addressed here:

  • An Elixir application defines an application callback function that is called when the VM starts any project, such as the main entry point of other languages. If you don't need to start your application, you don't need to implement the callback function. In this case, your code will amount to a simple bundle of modules and functions without any state.
  • The Mix compile task compiles our code to BEAM bytecode and places every module under a flat folder structure, automatically creating an .app file for our project, so that the VM knows how to start every needed application.
  • An...
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Key benefits

  • •Enhance your Elixir programming skills using its powerful tools and abstractions
  • •Discover how to develop a full-fledged file server
  • •Understand how to use Phoenix to create a web interface for your application.

Description

Running concurrent, fault-tolerant applications that scale is a very demanding responsibility. After learning the abstractions that Elixir gives us, developers are able to build such applications with inconceivable low effort. There is a big gap between playing around with Elixir and running it in production, serving live requests. This book will help you fll this gap by going into detail on several aspects of how Elixir works and showing concrete examples of how to apply the concepts learned to a fully ?edged application. In this book, you will learn how to build a rock-solid application, beginning by using Mix to create a new project. Then you will learn how the use of Erlang's OTP, along with the Elixir abstractions that run on top of it (such as GenServer and GenStage), that allow you to build applications that are easy to parallelize and distribute. You will also master supervisors (and supervision trees), and comprehend how they are the basis for building fault-tolerant applications. Then you will use Phoenix to create a web interface for your application. Upon fnishing implementation, you will learn how to take your application to the cloud, using Kubernetes to automatically deploy, scale, and manage it. Last, but not least, you will keep your peace of mind by learning how to thoroughly test and then monitor your application.

Who is this book for?

Mastering Elixir is for you if you have experience in Elixir programming and want to take it to the next level. This Elixir book shows you how to build, deploy, and maintain robust applications, allowing you to go from tinkering with Elixir on side projects to using it in a live environment. However, no prior knowledge of Elixir is required to enjoy the complex topics covered in the book.

What you will learn

  • •Use Elixir tools, including IEx and Mix
  • •Find out how an Elixir project is structured and how to create umbrella applications
  • •Discover the power of supervision trees, the basis for fault-tolerance
  • •Create a Domain-Specifc Language (DSL) that abstracts complexity
  • •Create a blazing-fast web interface for your application with Phoenix
  • •Set up an automatic deployment process for the cloud
  • •Monitor your application and be warned if anything unexpected happens
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Publication date, Length, Edition, Language, ISBN-13
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Length: 574 pages
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Language : English
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Product Details

Publication date : Jul 30, 2018
Length: 574 pages
Edition : 1st
Language : English
ISBN-13 : 9781788472678
Vendor :
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Table of Contents

12 Chapters
Preparing for the Journey Ahead Chevron down icon Chevron up icon
Innards of an Elixir Project Chevron down icon Chevron up icon
Processes – The Bedrock of Concurrency and Fault Tolerance Chevron down icon Chevron up icon
Powered by Erlang/OTP Chevron down icon Chevron up icon
Demand-Driven Processing Chevron down icon Chevron up icon
Metaprogramming – Code That Writes Itself Chevron down icon Chevron up icon
Persisting Data Using Ecto Chevron down icon Chevron up icon
Phoenix – A Flying Web Framework Chevron down icon Chevron up icon
Finding Zen through Testing Chevron down icon Chevron up icon
Deploying to the Cloud Chevron down icon Chevron up icon
Keeping an Eye on Your Processes Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
(2 Ratings)
5 star 50%
4 star 0%
3 star 50%
2 star 0%
1 star 0%
Tyler Munyon Jul 10, 2019
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Love the book so far, especially since we get to build an application that uses concepts that we are learning. Am wondering how to get the online version of the book on packt??
Amazon Verified review Amazon
Sean Bergstedt Apr 21, 2020
Full star icon Full star icon Full star icon Empty star icon Empty star icon 3
[REVISION]After re-referencing it a few more times, I've had time to reconsider my previous 1 star vote. There are some good sections on leveraging elixir's GenStage abstraction with Flow, which is unique and a pretty new addition to the Elixir scene. There are also some good sections on how to setup umbrella projects, how to integrate with SQL backend and best practices preserving coding style.The book is a bit rough around the edges, though, in terms of organization and just getting how the code works on your first read. Like I mentioned in my original review, you kind of have to hunt for what you want to learn and if you want to follow the code, you need to already have some familiarity with mix and the language. So, if you're just starting with Elixir, I'd recommend looking for one of the introductory books instead.[ORIGINAL]Lots of cross referencing and looking at the on-line source code to make sure your book code is tracking along nicely. Sometimes you have to look at something in later chapters in order to run code in earlier chapters. I ended up spending more time organizing the information the editors should have organized for me.I continue to be disappointed with Pakt Publishing. They just crank out books on volume instead of quality. At the end of the day, I don't blame the authors as I'm sure they spent a great deal of time on this, but the organization of code and flow of content is wildly out of sync with the quality one should expect for a book this price.
Amazon Verified review Amazon
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