Elixir Cookbook

Book Image

Elixir Cookbook

By : Paulo Pereira

Book Image

Elixir Cookbook

By: Paulo Pereira

Overview of this book

Elixir Cookbook

Elixir Cookbook

Credits

About the Author

About the Author

About the Reviewers

About the Reviewers

www.PacktPub.com

www.PacktPub.com

Preface

Free Chapter

Command Line

Using the terminal to prototype and test ideas

Loading and compiling modules

Getting help and accessing documentation within IEx

Using Erlang from Elixir

Inspecting your system in IEx

Inspecting your system with Observer

Creating a simple application

Managing dependencies

Generating a supervised application

Generating umbrella applications

Managing application configuration

Creating custom Mix tasks

Data Types and Structures

Data Types and Structures

Understanding immutability

Adding and subtracting lists

Combining tuples into a list

Creating and manipulating keyword lists

Using pattern matching

Pattern matching an HTTPoison response

Creating a key/value store with a map

Mapping and reducing enumerables

Generating lazy (even infinite) sequences

Streaming a file as a resource

Strings and Binaries

Strings and Binaries

Joining strings

Splitting strings

Replacing string codepoints with patterns

Slicing strings with ranges

Using regular expressions

Combining operations with the |> operator

Creating a word list

Determining the word frequency in a text

Reading and writing metadata from MP3 files

Modules and Functions

Modules and Functions

Namespacing modules

Using module attributes as constants

Enforcing behaviors

Documenting modules

Using module directives

Using a module in the scripted mode

Defining functions with default arguments

Using guard clauses and pattern matching in function definitions

Processes and Nodes

Processes and Nodes

Sending messages between processes

Making code run on all available CPUs

Using tasks to perform multiple concurrent computations

Creating a stateful server process (messages with counters)

Using agents as an abstraction around states

Using an ETS table to share the state

Creating named nodes

Connecting nodes

Executing code in a different node

OTP – Open Telecom Platform

OTP – Open Telecom Platform

Implementing a GenServer

Expanding our server

Creating a supervisor

Using Observer to inspect supervisors and processes

Handling errors and managing exceptions

Packaging and releasing an OTP application

Deploying applications and updating a running system

Cowboy and Phoenix

Cowboy and Phoenix

Setting up Cowboy

Serving static files

Implementing a websocket handler

Creating a Phoenix application

Defining routes

Creating a controller

Creating views and templates

Implementing topics

Protecting the Phoenix app with SSL

Interactions

Using Redis and Postgres

Using OS commands from within Elixir

Getting Twitter data

Installation and Further Reading

Installation and Further Reading

Installing Elixir

Installing PostgreSQL

Installing Redis

Some useful links

Index

Customer Reviews

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Using Observer to inspect supervisors and processes

The Observer tool we already used in a couple of recipes throughout the book allows us to have a better insight on supervision trees and to have information on the processes. It also allows us to "kill" a process and watch it be replaced by another one!

How to do it…

To start inspecting our supervisors and processes, we will follow these steps:

Open a new IEx session:
```
> iex
```
Start the Observer tool:
```
iex(1)> :observer.start
```
Select the Applications tab in the graphical interface.
In the logger application info, right-click on Elixir.Logger.Watcher and select the Kill process option, and then confirm the option in the popup.
Take a look at the PIDs for some processes. They have changed! This means that Elixir.Logger.Supervisor restarted some processes when one of its supervised processes terminated.
Note
We are the culprits for the failure but it serves the purpose of illustrating the power of a supervision tree and how it makes the task of...