Erlang 101 provides an overview of the Erlang programming language. It discusses Erlang's history and current status, key features like concurrency, distribution, and fault tolerance. These features make Erlang well-suited for building large, distributed, highly-available systems. Examples are given of companies using Erlang like Amazon, Facebook, Twitter, and of applications and frameworks built with Erlang like Apache CouchDB, RabbitMQ, and Riak. Resources for learning more about Erlang are also provided.

1. Erlang 101
Istanbul Hacker Space
https://istanbulhs.org/
25 Kasim 2012
Gokhan Boranalp
gokhan@zetaops.com

2. ● Nereden nereye.
○ Tarihçe ve şimdiki durum.
● Dil
● Önemli Noktalar
● Kullananlar
● Made with Erlang
● Sorular

3. Tarihçe

4. ● SHARED MEMORY WITH LOCKS
● SOFTWARE TRANSACTIONAL MEMORY
(STM)
● FUTURES, PROMISES, AND SIMILAR
● MESSAGE PASSING
Process Modelleri

5. Karakteristik Özellikler
■ Message Passing
■ Dynamic typed
■ Actor model
■ Share Nothing
■ Immutable Objects

6. Dil
1> io:format("Naber dunya~n").
Naber dunya
ok
2> io:format("Naber, ~s!~n", [kanka]).
Naber, kanka!
ok
- ~s = %s printf C
- ~n = n

7. Dil
Atoms
- true, false, test_me, kunthar@local, 'EXIT'
Integers
- 10, -200, 12345678909999999999999999999
- 16#FFffFFff=4294967295
- 16#FF= 255
- $A = 65 (ASCII kod A)
Floats
3.14
-0.123
299792458.0
6.022137e23
6.6720e-11

8. Dil
Tuples
- {1, 2, 3}
{bir, iki, uc, dort} {buradan, "IHS", "sizi selamlar"}
{complex, {nested, "structure", {here}}}
Lists
[]
[1, 2, 3]
[bir, iki, uc]
[[1,2,3],[4,5,6]]
[{yarin, "biraz oku"}, {sonra, "yuruyus yap"}, {enson, "otur da yaz"}]

9. Dil
String (list of ASCII codes)
"merhaba" = [$m, $e, $r, $h, $a, $b, $a] = [109,101,114,104,97,98,97]
Binaries
<<0, 1, 2, ..., 255>>
<<109,101,114,104,97,98,97>> = <<"merhaba">>
Binaries with Bit Syntax
<<1:1,32787:15>> = 2#1111111111111111
Diger Data Tipleri
Funs (lambda expression or closure)
Function-as-data-object

10. Dil
Pids (Process Identifiers)
self().
<0.31.0>
Ports
#Port<0.472>.
References
5> make_ref().
#Ref<0.0.0.42>

11. Noktalama
○ (.) when hariç herşeyi sonlandir
○ (;) koşulu sonlandır
○ (,) ifadeyi (expressions) sonlandır

12. List Comprehensions
{2n : n in L}
in Erlang:
○ brackets ({}) become square brackets ([]),
○ the colon (:) becomes two pipes (||)
○ and the word 'in' becomes the arrow (<-).
1> [2*N || N <- [1,2,3,4]].
[2,4,6,8]

13. List Operations

14. List Operations

15. Anonymous Functions

16. Functions

17. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Functional programming
language
○ High abstraction level
○ Pattern matching
○ Readable programs

18. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Solid concurrency model
○ Scales to handle complex
concurrency
○ Simple abstractions
Örnekler

19. spawn ile yeni bir process yaratmak
Pid = spawn(ex3,activity,[Joe,75,1024])
activity(Joe,75,1024)

20. Asenkron mesajlar

21. hard core concurrency

22. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Lightweight processes
○ Fast message passing
○ Response times in the order of
milliseconds efficient garbage
collection
Oynat Uğurcuğum

23. process creation times

24. message passing times

25. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Simple and consistent error
recovery
○ Supervision hierarchies
Örnekler

26. process'ler birbirine bağlı çalışabilir!

27. proses hata kontrolü
- Proses sonlandığında, bağlı tüm proseslere exit sinyali
gönderilir.

28. hata kontrolü (2)
- Exit sinyalleri "tuzaklanarak" (trap) messages şeklinde alınabilir.

29. Supervisors & Workers

30. Error handling
● No global variables -- fewer side-effects
● No direct memory access -- no pointer errors
● No malloc/free bugs
● Solid concurrency model -- reduces synchronization
problems, reduces the state space (simpler programs)
● Fault isolation -- memory-protected lightweight
processes
● Built-in error recovery support -- more consistency
Concurrency & Fault Tolerance were designed into the
language from the start!

31. Debugging and Profiling Support
● Symbolic crash reports
○ Usually sufficient info to locate bugs within minutes
● Built-in trace support
○ Function calls (ability to filter on module name,
function and args)
○ Messages (+ sequence trace)
○ Process events (context switch, spawn, link, exit)
○ Garbage collections
○ Optionally with timestamps (can be used for profiling,
benchmarks)
○ Trace to process, file, or port (network socket)
○ Also available on live systems

32. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Explicit or transparent
distribution
○ Network-aware runtime
system
Örnekler

33. Transparent Distribution
- başka bir bilgisayara prosesler arası mesaj gönderimi, aynı
bilgisayarda mesaj gönderimi kadar kolaydır.

34. Simple RPC

35. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Easily change code in a
running system
○ Enables non-stop operation
○ Simplifies testing

36. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Ports to the outside world
○ behave as Erlang processes
- Erlang Port Drivers

37. Erlang Önemli Noktalar
● Declarative
● Concurrency
● Soft real-time
● Robustness
● Distribution
● Hot code loading
● External Interfaces
● Portability
○ Any UNIX
○ Windows
○ VxWorks etc.

38. Systems Overview

39. Erlang/OTP (Open Telecom Platform)
● Middleware for Erlang development
● Designed for fault tolerance and portability
● Behaviors: A formalization of design patterns
● Components
○ Error handling, reporting and logging
○ Mnesia, distributed real-time database management
system CORBA, IDL Compiler, Java & C Interface Support
○ HTTP Server + Client, FTP Client
○ SNMP Agent + ASN.1 Compiler
○ H.248
○ XML
○ ...

40. OTP Behaviors
● "A formalization of design patterns"
○ A framework + generic code to solve a common problem
○ Built-in support for debugging and software upgrade
○ Makes it easier to reason about the behavior of a program
● Examples of OTP behaviors
application defines how an application is implemented
supervisor used to write fault-tolerant supervision trees
gen_server for writing client-server applications
gen_event for writing event handlers
gen_fsm for finite state machine programming

41. Büyük Projelerde Erlang
● Easy to build a first runnable application
● Easy to debug
● Easy to maintain
● Very strong support for fault tolerance
● Suitable for large systems/projects
● Great for prototyping
● Impressive performance/scalability in real applications
Outstanding tool for test automation
● High programmer satisfaction

42. Kullananlar
● Amazon Web Servisleri - SQS ve SimpleDB
● Facebook, chat
● Twitter
● Mochimedia
● del.icio.us / Yahoo
● T-Mobile
● Telia
● Bluetail/Alteon/Nortel
● Github

43. Made with Erlang
○ Apache CouchDB – document-based DB with REST
○ Disco – Map/Reduce framework for Erlang
○ Fuzed – Generic clustering framework (Powerset)
○ Mochiweb – Fast lightweight web server framework
(like Java Servlets for Erlang)
○ DHT – Distributed Key/Value Stores – 90% of all
implementations in Erlang – Dynomite, Scalaris, etc.
○ Yaws web server
○ Cowboy
○ Nitrogen
○ RabbitMQ
○ Riak

44. Good fit for
● Irregular concurrency
○ Task-level parallelism
○ Fine-grained parallelism
● Network servers
● Distributed systems
● Middleware:
○ Parallel databases
○ Message Queue servers
● Soft Real-Time / Embedded applications
● Monitoring, control and testing tools

45. Kaynaklar
http://en.wikipedia.org/wiki/Abstraction_%28computer_science%29
http://is.gd/xHWvZ3
http://www.erlang.org
http://learnyousomeerlang.com/