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ELIXIR/PHOENIXBUILD YOUR OWN REAL-TIME WEB SERVICE WITH
PRESENTED BY: CHI-CHI EKWEOZOR AT:
MANCHESTER LAMBDA LOUNGE MON 17 OCT 2016
TODAY’S WEB:
Hundreds of millions of interconnected services continuously exchanging data.
Reliability, concurrency, fault-tolerance, scalability, all expected as the norm.
WHY ELIXIR? WHY PHOENIX?
BUILDING REAL-TIME WEB SERVICES
ABOUT ME:
▸ Chi-chi Ekweozor (@thisischichi):
▸ Contract Software engineer - C/C++, PHP, JavaScript, and now Elixir
▸ Previously a social media marketing consultant!
▸ Combined social media know how with Elixir/Phoenix to create Assenty, a real-time Question & Answer tool for event organisers.
INTENDED AUDIENCE:
This talk is intended for web developers with some familiarity with functional programming concepts.
It is a high level overview of the Phoenix web framework which is written in Elixir, a relatively new functional programming language.
No prior experience with Elixir is required.
WE’LL COVER:
▸ Why Elixir?
▸ What is Phoenix?
▸ What are Phoenix Channels?
▸ How do they work?
▸ Assenty Live Demo: Phoenix Channels in Production
IS IT FUNCTIONAL?WHY ELIXIR?
ELIXIR IS A DYNAMIC, FUNCTIONAL LANGUAGE DESIGNED FOR BUILDING …
elixir-lang.org
ELIXIR LEVERAGES THE ERLANG VM, KNOWN FOR RUNNING LOW-LATENCY,
elixir-lang.org
DISTRIBUTED AND FAULT-TOLERANT SYSTEMS, WHILE ALSO BEING SUCCESSFULLY
elixir-lang.org
ELIXIR’S STRENGTHS:
WHY ELIXIR?
▸ An extensible and well-documented dynamic language with Ruby-inspired syntax, undergirded by Erlang’s 30 year old, tried and tested virtual machine known as BEAM
▸ In-built pattern matching and the pipe operator |> makes it easy to work with and reason about immutable data
▸ Mix: an impressive tooling ecosystem that adds rock solid libraries for authentication, metrics, crypto, embedded systems support and much more
RATIONALE FOR CREATING ELIXIR:
“WHEN DESIGNING THE ERLANG LANGUAGE AND THE ERLANG VM,
José Valim, creator, Elixir
JOE, MIKE AND ROBERT DID NOT AIM TO IMPLEMENT A FUNCTIONAL PROGRAMMING LANGUAGE,
José Valim, creator, Elixir
THEY WANTED A RUNTIME WHERE THEY COULD BUILD DISTRIBUTED, FAULT-TOLERANT APPLICATIONS.
José Valim, creator, Elixir
IT JUST HAPPENED THAT THE FOUNDATION FOR WRITING SUCH SYSTEMS SHARE MANY OF THE FUNCTIONAL
José Valim, creator, Elixir
PROGRAMMING PRINCIPLES. AND IT REFLECTS IN BOTH ERLANG AND ELIXIR.
José Valim, creator, Elixir
BENEFIT OF CODING IN ELIXIR:
AT LEAST TWO THINGS YOU STAND TO GAIN WITH ELIXIR:
▸ Because of data immutability, concurrency is a lot easier to understand, and use:
▸ Your application or program will use all available cores on your machine to function. It just does.
▸ A single function definition lets you define different implementations depending on its arguments:
▸ Your application or program will be easier to modularise and test.
WE’LL COVER:
▸ Why Elixir?
▸ What is Phoenix?
▸ What are Phoenix Channels?
▸ How do they work?
▸ Assenty Live Demo: Phoenix Channels in Production
IS IT REAL-TIME?AND THIS PHOENIX?
INTRODUCING PHOENIX:
▸ Phoenix is a web development framework written in Elixir which implements the server-side MVC pattern.
▸ Many of its components and concepts will seem familiar to those of us with experience in other web frameworks like Ruby on Rails or Python's Django.
▸ Phoenix is made up of a number of distinct parts, each with its own purpose and role to play in building a web application.
Excerpted from the Phoenix Framework Guides
ENDPOINTPHOENIX FRAMEWORK COMPONENT:
HANDLES ALL ASPECTS OF REQUESTS UP UNTIL THE POINT WHERE THE ROUTER TAKES OVER
ROUTERPHOENIX FRAMEWORK COMPONENT:
PARSES INCOMING REQUESTS AND DISPATCHES THEM TO THE CORRECT CONTROLLER/ACTION, PASSING PARAMETERS AS NEEDED
MODELSPHOENIX FRAMEWORK COMPONENT:
USES ECTO, AN ELIXIR FRAMEWORK FOR PERSISTENCE TO READ AND PERSIST DATA TO AN UNDERLYING DATABASE
CONTROLLERSPHOENIX FRAMEWORK COMPONENT:
PROVIDE FUNCTIONS, CALLED ACTIONS, TO HANDLE REQUESTS
VIEWSPHOENIX FRAMEWORK COMPONENT:
RENDER TEMPLATES AND ACT AS A PRESENTATION LAYER
TEMPLATESPHOENIX FRAMEWORK COMPONENT:
HTML FILES INTO WHICH WE PASS DATA TO FORM COMPLETE HTTP RESPONSES
CHANNELSPHOENIX FRAMEWORK COMPONENT:
MANAGE (WEB) SOCKETS FOR EASY REAL-TIME COMMUNICATION
PUBSUBPHOENIX FRAMEWORK COMPONENT:
UNDERGIRDS THE CHANNEL LAYER AND ALLOWS CLIENTS TO SUBSCRIBE TO TOPICS
WE’LL COVER:
▸ Why Elixir?
▸ What is Phoenix?
▸ What are Phoenix Channels?
▸ How do they work?
▸ Assenty Live Demo: Phoenix Channels in Production
WHAT ARE PHOENIX CHANNELS?
▸ Channels are a really exciting and powerful part of Phoenix that allow us to easily add soft real-time features to our applications.
▸ Channels are based on a simple idea - sending and receiving messages. Senders broadcast messages about topics.
▸ Receivers subscribe to topics so that they can get those messages. Senders and receivers can switch roles on the same topic at any time.
Excerpted from the Phoenix Framework Guides
CHARACTERISTICS OF SOFT REAL-TIME SYSTEMS:
▸ You don’t have to hit every deadline, as opposed to the case in hard real-time systems.
▸ Performance will degrade if too many are missed but results are still valid after the deadline.
▸ Examples: airline reservation systems.
▸ Contrast with hard real-time systems where you must absolutely hit every deadline. Examples: nuclear systems, aircraft control systems, defence applications.
TRADITIONAL STATELESS REQUEST-RESPONSE MODEL:Image taken from Programming Phoenix by Chris McCord, Bruce Tate, and José Valim
PHOENIX CHANNELS GIVE YOU STATEFUL CONVERSATIONS:Image taken from Programming Phoenix by Chris McCord, Bruce Tate, and José Valim
A SINGLE CLIENT ON A PAGE CONNECTS DIRECTLY WITH A PROCESS ON THE SERVER…
Chris McCord, Phoenix creator
CALLED A CHANNEL.
Chris McCord, Phoenix creator
SINCE ELIXIR CAN SCALE TO MILLIONS OF SIMULTANEOUS PROCESSES THAT MANAGE
Chris McCord, Phoenix creator
MILLIONS OF CONCURRENT CONNECTIONS, YOU DO NOT HAVE TO RESORT TO THE …
Chris McCord, Phoenix creator
REQUEST/RESPONSE MODEL TO MAKE THINGS EASY TO SCALE OR EVEN MANAGE.
Chris McCord, Phoenix creator
A CLIENT CONNECTS TO A CHANNEL AND THEN SENDS AND RECEIVES MESSAGES.
Chris McCord, Phoenix creator
THAT’S IT.
Chris McCord, Phoenix creator
WHAT PHOENIX CHANNELS MAKE POSSIBLE:
▸ With Channels, neither senders nor receivers have to be Elixir processes.
▸ They can be anything that we can teach to communicate over a Channel - a JavaScript client, an iOS app, another Phoenix application, our watch.
▸ Whereas request/response interactions are stateless, conversations in a long-running process can be stateful.
Excerpted from the Phoenix Framework Guides
WE’LL COVER:
▸ Why Elixir?
▸ What is Phoenix?
▸ What are Phoenix channels?
▸ How do they work?
▸ Assenty Live Demo: Phoenix Channels in Production
WHAT’S INSIDE?UNDERSTANDING PHOENIX CHANNELS
HOW DO PHOENIX CHANNELS WORK?
▸ A Phoenix channel is a conversation.
▸ The channel sends messages, receives messages, and keeps state. We call the messages events.
▸ A Phoenix conversation is about a topic, and it maps onto application concepts like a chat room, a game, or in Assenty's case, the question board for an event.
Excerpted from Programming Phoenix by Chris McCord, Bruce Tate, and José Valim
BENEFIT OF USING PHOENIX CHANNELS:
▸ For sophisticated user interactions like interactive pages or multiplayer games, you don’t have to work so hard to keep track of the conversation by using cookies, databases, or the like.
▸ Each call to a channel simply picks up where the last one left off.
▸ A client establishes a new connection with a web socket. That socket is transformed through the life of the conversation with the server.
Excerpted from Programming Phoenix by Chris McCord, Bruce Tate, and José Valim
COMPONENTS OF A PHOENIX CHANNEL:
USER SOCKETPHOENIX CHANNEL COMPONENT:
THIS MODULE SERVES AS THE STARTING POINT FOR ALL SOCKET CONNECTIONS
RESPONSIBLE FOR AUTHENTICATING, IT ALSO DEFINES THE TRANSPORT
LAYERS THAT WILL HANDLE THE CONNECTION BETWEEN THE CLIENT AND THE SERVER.
TOPICPHOENIX CHANNEL COMPONENT:
JUST AS A CONTROLLER PASSES AN ID PARAMETER TO REPRESENT A RESOURCE
FOR A CONTROLLER, WE USE A TOPIC ID TO SCOPE A CHANNEL CONNECTION.
WHEN CLIENTS JOIN A CHANNEL, THEY MUST PROVIDE A TOPIC. CLIENTS CAN JOIN
ANY NUMBER OF CHANNELS AND ANY NUMBER OF TOPICS ON A CHANNEL.
CHANNELPHOENIX CHANNEL COMPONENT:
THIS MODULE ALLOWS CONNECTIONS AND LETS USERS DISCONNECT AND SEND EVENTS
IT SUPPORTS 4 CALLBACKS: JOIN(), HANDLE_IN(), HANDLE_OUT(), HANDLE_INFO()
1. JOIN(): CLIENTS JOIN TOPICS ON A CHANNEL
2. HANDLE_IN(): RECEIVES DIRECT CHANNEL EVENTS
3. HANDLE_OUT(): INTERCEPTS BROADCAST EVENTS
4. HANDLE_INFO(): RECEIVES PLATFORM (OTP) MESSAGES
CLIENT LIBRARYPHOENIX CHANNEL COMPONENT:
A CONSTRUCT THAT CAN CONNECT DIRECTLY TO THE SERVER
PHOENIX CURRENTLY SHIPS WITH ITS OWN JAVASCRIPT CLIENT.
IOS, ANDROID, AND C# CLIENTS HAVE BEEN RELEASED WITH PHOENIX 1.0.
YOUR CLIENT CODEPHOENIX CHANNEL COMPONENT:
THIS JAVASCRIPT OBJECT ADDS REAL-TIME FUNCTIONALITY TO YOUR APPLICATION BY LISTENING FOR EVENTS GENERATED BY THE CALLBACKS (JOIN(), HANDLE_* ETC) DEFINED IN ELIXIR AND RESPONDING APPROPRIATELY.
WE’LL COVER:
▸ Why Elixir?
▸ What is Phoenix?
▸ What are Phoenix channels?
▸ How do they work?
▸ Assenty Live Demo: Phoenix Channels in Production
WHAT IS ASSENTY?
▸ Assenty is a real-time question and answer tool for event organisers.
▸ Written in Elixir, and running on the Phoenix framework, it provides a platform for capturing and persisting questions posted to an event’s ‘question board’
▸ A question board is an online archive of questions and answers discussed at a physical or virtual event.
▸ As each question and answer submitted to a question board is persisted to the database, it is easily shared via social media.
PHOENIX CHANNELS LIVE DEMO:
▸ Visit the Question Board created during the live demo
▸ Thank you to all the participants!
THE ENDTHAT’S ALL FOLKS!
REFERENCES & RESOURCES
▸ Elixir website http://elixir-lang.org/
▸ On Functional Elixir http://blog.plataformatec.com.br/2016/05/beyond-functional-programming-with-elixir-and-erlang/
▸ Elixir Guides http://elixir-lang.org/getting-started/introduction.html
▸ Phoenix Overview http://www.phoenixframework.org/docs/overview
▸ Erlang and Functional Programming link
