Gain insights into building scalable backend applications with Elixir, OTP, and Phoenix. Learn about persistent connections via Phoenix Channels, and explore distinct, decoupled application layers.

Functional Web Development with  Elixir, OTP and Phoenix by The Pragmatic Programmer_ .png

elixir_islands_test.tar.gz

elixir-app

pheonix-app

elixir-app-guesses

island-interface

phoenix-app-compiled

phoenix-app-iex

phoenix-app-form

phoenix-app-new-module

client-connection

presence

phoenix-app-final

without-presence

Elixir and OTP provide exceptional tools to build rock-solid backend applications that scale. In this course, you’ll build a web application in a radically different way, with a backend that holds application state. You’ll use persistent Phoenix Channel connections instead of HTTP’s request-response, and create the full application in distinct, decoupled layers.

In Part 1, you’ll start by building the business logic as a separate application, without Phoenix. You’ll model the application domain with Elixir functions and simple data structures.

In Part 2, you’ll add in the GenServer Behaviour to make managing in-memory state a breeze. 

In Part 3, you’ll build a web interface with Phoenix where you’ll use Phoenix Channels to establish persistent connections between the stateful server and a stateful front-end client.

Needless to say, you’re going to love this way of building web apps!

Functional Web Development with Elixir, OTP and Phoenix

## Start dependency inside the BEAM

Applications are so independent, we can start and stop them individually in the BEAM. When we start an individual Application, OTP will start any necessary supervisor or worker processes with it. When we stop that same Application, OTP makes sure to stop those supervisors and workers as well.

The work of defining which processes to start comes together in the callbacks file. In the `IslandsEngine` project, that’s `/lib/islands_engine/application.ex`.

Back in [Process Supervision for Recovery](https://www.educative.io/courses/functional-web-development-elixir-otp-phoenix/introduction),  we took a good look at this file in the context of supervision trees. We won’t need to go over it in much detail, but we should point out the `use Application` line that makes this module an Application Behaviour.

We should also quickly mention the `start/2` function, which is there to start the top-level supervisor for the Application. Along the way, it makes sure that any child processes—supervisors or workers—start as well.

# Start dependency inside the BEAM

Applications are so independent, we can start and stop them individually in the BEAM. When we start an individual Application, OTP will start any necessary supervisor or worker processes with it. When we stop that same Application, OTP makes sure to stop those supervisors and workers as well.

The work of defining which processes to start comes together in the callbacks file. In the `IslandsEngine` project, that’s `/lib/islands_engine/application.ex`.

Back in [Process Supervision for Recovery](https://www.educative.io/courses/functional-web-development-elixir-otp-phoenix/introduction),  we took a good look at this file in the context of supervision trees. We won’t need to go over it in much detail, but we should point out the `use Application` line that makes this module an Application Behaviour.

We should also quickly mention the `start/2` function, which is there to start the top-level supervisor for the Application. Along the way, it makes sure that any child processes—supervisors or workers—start as well.

Understand the details of starting and stopping applications in IslandsEngine.

Introduction

Mapping Our Route

Model Data and Behavior

Working of State Machines

Add OTP for Concurrency and Fault Tolerance

Process Supervision for Recovery

Generate a New Web Interface with Phoenix

Create Persistent Connections with Phoenix Channels

Appendix

Start and Stop Applications

Start dependency inside the BEAM