Erlang 101 giriş semineri istanbul hackerspace

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/