1. Erlang Open Telecom Platform EAB/UPD/S Ulf Wiger

3. History of Erlang 1984-86: Experiments programming POTS with several languages 1998: Open Source Erlang 1987: Early Erlang Prototype projects 1991: First fast implementation 1993: Distributed Erlang 1995: Several new projects 1996: Open Telecom Platform AXD and GPRS started How to design SW for future telecoms systems?

7. Pattern Matching and Single Assignment

8. List Operations

9. List Operations (2)

10. List Comprehensions

11. Anonymous Functions

12. Functions (cont.)

15. Erlang Example Creating a new process using spawn -module(ex3). -export([activity/3]). activity(Name,Pos,Size) -> ………… Pid = spawn(ex3,activity,[Joe,75,1024]) activity(Joe,75,1024)

16. Erlang Example Processes communicate by asynchronous message passing Pid ! {data,12,13} receive {start} -> ……… {stop} -> ……… {data,X,Y} -> ……… end receive {start} -> ……… {stop} -> ……… {data,X,Y} -> ……… end

17. Erlang Examples 4 Concurrency - Finite State Machine ringing_B_side(PidA) -> receive {lim, offhook} -> lim:stop_ringing(), PidA ! {hc, {connect, self()}}, speech(PidA); {hc, {cancel, PidA}} -> cancel(PidA); {lim, {digit, _Digit}} -> ringing_B_side(PidA); {hc, {request_connection, Pid}} -> Pid ! {hc, {reject, self()}}, ringing_B_side(PidA) after 30000 -> cancel(PidA) end. Selective receive True encapsulation of sub-states Optional timeout Asynchronous send

19. Process creation times (LOG/LOG scale) Source: Joe Armstrong SICS > 200,000 processes 10 100 1,000 10,000 100,000 Number of processes 1 10 100 1,000 Microseconds/process erlang java C#

20. Message passing times (LOG/LOG scale) Source: Joe Armstrong SICS > 200,000 processes 10 100 1,000 10,000 100,000 Number of processes 1 10 1,000 100,000 Microseconds/message erlang java C# 10,000 100 1

22. Erlang Example Cooperating processes may be linked together using spawn_link(…,…,…) or link(Pid)

23. Erlang Example When a process terminates, an exit signal is sent to all linked processes … and the termination is propagated

24. Erlang Example Exit signals can be trapped and received as messages receive {‘EXIT’,Pid,...} -> ... end process_flag(trap_exit,true), ...

25. Erlang Example Robust systems can be built by layering “ Supervisors” “ Workers”

29. Transparent Distribution Erlang Run-Time System Erlang Run-Time System B ! Msg network C ! Msg Message passing between processes in different computer is just as easy as between processes in the same computer A B C

30. Simple RPC loop() -> receive {From, {apply, M, F, A}} -> Answer = (catch apply(M, F, A)), From ! {rex, node(), Answer} loop(); _Other -> loop() end. {rex, Node} ! {self(), {apply, M, F, A}}, receive {rex, Node, What} -> What end {rex, Node} ! {self(), {apply, M, F, A}}, receive {rex, Node, What} -> What end {rex, Node} ! {self(), {apply, M, F, A}}, receive {rex, Node, What} -> What end loop() -> receive {From, {apply, M, F, A}} -> Answer = (catch apply(M, F, A)), From ! {rex, node(), Answer} loop(); _Other -> loop() end. loop() -> receive {From, {apply, M, F, A}} -> Answer = (catch apply(M, F, A)), From ! {rex, node(), Answer} loop(); _Other -> loop() end. loop() -> receive {From, {apply, M, F, A}} -> Answer = (catch apply(M, F, A)), From ! {rex, node(), Answer} loop(); _Other -> loop() end.

32. Erlang Example Version 1 Version 2 change_code

34. Erlang Example Port External process Port ! {self(), {command, [1,2,3]}}

35. Erlang Example Port External process receive {Port, {data, Info}} -> end A port can use e.g. a TCP, UDP, SSL socket, UNIX pipe, or custom transport (e.g. SAAL)

37. Systems Overview OTP Components Standard Libraries Erlang Run-Time System Hardware and Operating System Applications written in Erlang Applications written in C, C++ or Java

43. Downloads since Open Source Launch ’98 Grouping: 6 months

49. Questions?