slidenumbers: true Erlang.

Fault-tolerant, concurrent programming.

A brief history of Erlang

^ Telefontornet in Stockholm, around 1890. Used until 1913.

^ Telephones were operated manually at Switchboards. Anyone old enough to remember? I'm certainly not.

fit

^ Eventually we did that in software, and we got better at it over time. Ericsson AXD 301, first commercial Erlang switch. But lets take a step back.

Phone switches must be ...

Highly concurrent

Fault-tolerant

Distributed

(Fast!)

right 150%

... and so is Erlang!

Erlang as a whole:

Unique process model (actors!)
Built-in fault-tolerance & error handling
Distributed processes
Three parts!

Part 1: Erlang, the language

Functional
Prolog-inspired syntax
Everything is immutable
Extreme pattern-matching

Hello Joe

hello_joe.

Hello Joe

-module(hello1).
-export([hello_joe/0]).

hello_joe() ->
    hello_joe.

Hello Joe

-module(hello1).
-export([hello_joe/0]).

hello_joe() ->
    hello_joe.
    
% 1> c(hello1).
% {ok,hello1}
% 2> hello1:hello_joe().
% hello_joe

Hello Joe

-module(hello2).
-export([hello/1]).

hello(Name) ->
    io:format("Hello ~s!~n", [Name]).

% 3> c(hello2).
% {ok,hello2}
% 4> hello2:hello("Joe").
% Hello Joe!
% ok

[fit] Hello world Joe is boring!

[fit] Lets do it with processes.

Hello Server

-module(hello_server).
-export([start_server/0]).

start_server() ->
    spawn(fun() -> server() end).

server() ->
    receive
        {greet, Name} ->
            io:format("Hello ~s!~n", [Name]),
            server()
    end.

[fit] Some issues with that ...

What about unused messages?
What if the server crashes?

[fit] Part 2: Open Telecom Platform

It's called Erlang/OTP for a reason.

OTP: An Application Framework

Supervision - keep processes alive!
OTP Behaviours - common process patterns
Extensive standard library
Error handling, debuggers, testing, ...
Lots more!

^ Standard library includes lots of things from simple network libraries over testing frameworks to cryptography, complete LDAP clients etc.

Supervision

inline

^ Supervision keeps processes alive, different restart behaviours, everything should be supervised to avoid "process" (and therefore memory) leaks

OTP Behaviours

gen_server
gen_statem
gen_event
supervisor

^ gen = generic. explain server, explain statem, event = event handling with registered handlers, supervisor ...

gen_server

[fit] Part 3: BEAM

Bogdan/Bjørn Erlang Abstract machine

A VM for Erlang

Many were written, BEAM survived
Concurrent garbage-collection
Lower-level bytecode than JVM
Very open to new languages (Elixir, LFE, Joxa, ...)

What next?

Ole's talk, obviously!
Learn You Some Erlang! www.learnyousomeerlang.com
Watch Erlang the Movie
(soon!) Join the Oslo BEAM meetup group

[fit] Questions?

@tazjin