222 lines
3.5 KiB
Markdown
222 lines
3.5 KiB
Markdown
slidenumbers: true
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Erlang.
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======
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### Fault-tolerant, concurrent programming.
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---
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## A brief history of Erlang
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---
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^ Telefontornet in Stockholm, around 1890. Used until 1913.
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---
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^ Telephones were operated manually at Switchboards. Anyone old enough to remember? I'm certainly not.
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---
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^ 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.
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---
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## Phone switches must be ...
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Highly concurrent
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Fault-tolerant
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Distributed
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(Fast!)
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---
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## ... and so is Erlang!
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---
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## Erlang as a whole:
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- Unique process model (actors!)
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- Built-in fault-tolerance & error handling
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- Distributed processes
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- Three parts!
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---
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## Part 1: Erlang, the language
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- Functional
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- Prolog-inspired syntax
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- Everything is immutable
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- *Extreme* pattern-matching
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---
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### Hello Joe
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```erlang
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hello_joe.
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```
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---
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### Hello Joe
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```erlang
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-module(hello1).
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-export([hello_joe/0]).
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hello_joe() ->
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hello_joe.
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```
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---
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### Hello Joe
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```erlang
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-module(hello1).
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-export([hello_joe/0]).
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hello_joe() ->
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hello_joe.
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% 1> c(hello1).
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% {ok,hello1}
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% 2> hello1:hello_joe().
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% hello_joe
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```
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---
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### Hello Joe
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```erlang
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-module(hello2).
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-export([hello/1]).
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hello(Name) ->
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io:format("Hello ~s!~n", [Name]).
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% 3> c(hello2).
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% {ok,hello2}
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% 4> hello2:hello("Joe").
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% Hello Joe!
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% ok
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```
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---
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## [fit] Hello ~~world~~ Joe is boring!
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## [fit] Lets do it with processes.
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---
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### Hello Server
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```erlang
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-module(hello_server).
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-export([start_server/0]).
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start_server() ->
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spawn(fun() -> server() end).
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server() ->
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receive
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{greet, Name} ->
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io:format("Hello ~s!~n", [Name]),
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server()
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end.
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```
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---
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## [fit] Some issues with that ...
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- What about unused messages?
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- What if the server crashes?
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---
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## [fit] Part 2: Open Telecom Platform
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### **It's called Erlang/OTP for a reason.**
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---
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# OTP: An Application Framework
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- Supervision - keep processes alive!
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- OTP Behaviours - common process patterns
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- Extensive standard library
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- Error handling, debuggers, testing, ...
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- Lots more!
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^ Standard library includes lots of things from simple network libraries over testing frameworks to cryptography, complete LDAP clients etc.
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---
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# Supervision
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^ Supervision keeps processes alive, different restart behaviours, everything should be supervised to avoid "process" (and therefore memory) leaks
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---
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# OTP Behaviours
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* `gen_server`
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* `gen_statem`
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* `gen_event`
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* `supervisor`
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^ gen = generic. explain server, explain statem, event = event handling with registered handlers, supervisor ...
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---
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`gen_server`
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---
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## [fit] Part 3: BEAM
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### Bogdan/Bjørn Erlang Abstract machine
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---
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## A VM for Erlang
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* Many were written, BEAM survived
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* Concurrent garbage-collection
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* Lower-level bytecode than JVM
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* Very open to new languages
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(Elixir, LFE, Joxa, ...)
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---
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## What next?
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* Ole's talk, obviously!
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* Learn You Some Erlang!
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www.learnyousomeerlang.com
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* Watch *Erlang the Movie*
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* (soon!) Join the Oslo BEAM meetup group
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---
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# [fit] Questions?
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`@tazjin`
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