OTP Course

What's in this preview?

We want you to get the feel for typical Groxio content and the reasons we provide each type of content. Each Groxio module comes in four scheduled releases consisting of the central PDF, videos, and resource links. Later releases have projects as well. You can see part of the first release here.

Did you try turning it off and on again?

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Programmer Passport OTP

Why a book?

The scientific teaching method we follow is the Dreyfus learning model. Books provide the metaphors experts need to build context, step-by-step instructions for beginners, and the exercises that intermediates need to learn.


1. OTP Basics

Why an itinerary?

The itinerary is a virtual guide. This optional list describes the highlights of each release to maximize your learning time.


OTP is the heart and soul of Elixir’s concurrency and reliability. It is based on 30 years of experience with the Erlang framework that provided the core reliability and availability of Erickson phone switches for many years. OTP gets its reliability by separating the concerns of reusable project lifecycle from project custom code.

Elixir developers use OTP by creating a generic service layer and then augmenting that template with their own custom code. Instead of starting their own application directly, they use a supervisor, a process server of sorts that knows how to stop, start, and detect failure in processes.

This slight separation may seem like a small thing, but it is the basis of extraordinary availability metrics for the Erlang language. You can leverage OTP to build your own services into your own Elixir applications, whether you’re using Phoenix, Nerves, or some other kind of service.


In 1988, Joe Armstrong, Robert Virding, and Michael Williams were working on making software more reliable at Ericsson. They built a library called the Open Telecom Protocol. That acronym was an exercise in marketing, but the acronym was eventually dropped.

The project was opensourced as part of the Erlang project, and the popularity of the programming framework began to pick up. In 2012, Elixir was created, expanding OTP’s footprint. Scala’s Akka framework extends OTP to the Java virtual machine.


Public & Private

Why videos?

Groxio language modules have two kinds of videos. Our overview videos set the history and context of a language, or wrap up the work we've done, and are free to support language ecosystems. Our coding instruction videos, mostly starting with the second release, are paid content, and each one offers a live coding project.

Every learning level benefits from pair programming. Our videos are professional, but do not scrub away every tiny mistake. That way, you can see how experienced programmers deal with errors and changes in code organization.


3. When Not to OTP

Sometimes, OTP looks too much like a golden hammer. When you have a golden hammer, everything looks like a nail. In this video, you'll learn why some applications are *not* nails. This video will walk you through an example that intentionally builds in a race condition.
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2. mix new --sup

When the mix tool was created, projects always had a supervisor. Shortly after, supervisors were removed in favor of the --sup flag. This video will show you precisely what happens when you create a project with --sup. You will find out how Elixir builds OTP applications, and what you need to do to integrate them.

1. OTP. Did you try turning it off and on again?

OTP is the reason Erlang developers say to "Just let it crash." In this video, you'll learn why. Rather than building an application in a process and starting it direcly, OTP has a *process server* called a supervisor that's responsible for the whole application lifecycle. In short, the supervisor knows how to "turn it off and on again!"

0. Bring On the Workerbees

If you like what you find here and want to design software concepts that use these systems, you can use this book that teaches you how to build software using the layered approach talked about in these videos and the book. This video talks about the layers you'll find in there.

Community Resources

Cool quick trips for OTP

Why resource links?

Each new chapter has a set of links, separated into three categories. The categories reflect different competency levels and resources that match that stage of learning, for each Groxio release.

Learn It

These resources will get you on the path to learning with background information, tooling and exercises.

Do It

You decide how deep to go. These resources are exercises and projects to cement your learning.

Grok It

These resources will help you put your new knowledge into context so you'll be better at your everyday job.


Longer Excursions (chapters 3 and 4)

Why projects?

The Dreyfus model is originally instruction for pilots. A typical pilot course is based on reading material to understand context, and then flying a plane. Our videos and PDFs are important, but in the end, programmers need to program in order to learn. Our projects offer different levels of assistance, from "give me the answer" to "make this test pass".