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

# Channel module

The first thing we need is a Channel module. Let’s get one started at `islands_interface/lib/islands_interface_web/channels/game_channel.ex`:
```Elixir
defmodule IslandsInterfaceWeb.GameChannel do
  use IslandsInterfaceWeb, :channel

  alias IslandsEngine.{Game, GameSupervisor}
```

To make it behave like a Channel, we use `IslandsInterfaceWeb :channel`. This triggers the existing `channel/0` function in the `IslandsInterfaceWeb` module, located at `islands_interface/lib/islands_interface_web/islands_interface_web.ex`.

```Elixir
def channel do
  quote do
    use Phoenix.Channel
    import IslandsInterfaceWeb.Gettext
  end
end
```

We later work with the `Game` and `GameSupervisor` modules, so we need to alias them here.

With the proto-Channel module in place, there are two pieces of housekeeping we need to check in on routing requests to our socket and registering our Channel with a socket.

The “route” to our socket appears in our project’s endpoint at `islands_interface/lib/islands_interface_web/endpoint.ex`. Phoenix generates this for us when it create our project:

```Elixir
defmodule IslandsInterfaceWeb.Endpoint do
  use Phoenix.Endpoint, otp_app: :islands_interface
  socket "/socket", IslandsInterface.UserSocket
```

Let's define a new module in the game code.

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

Define a New Module

Channel module