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tvl-depot/users/tazjin/presentations/erlang-2016/presentation.md
Vincent Ambo 2e3b03b5ae chore(tazjin): Move my presentations to my user directory 
Change-Id: I72b25680e7167c3a55477111c28b1d4936c60e2c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/606
Reviewed-by: tazjin <mail@tazj.in>
2020-06-26 19:51:51 +00:00

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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